]> git.sur5r.net Git - openocd/blobdiff - src/jtag/drivers/stlink_usb.c
jtag: drivers: stlink: handle all versions with single config
[openocd] / src / jtag / drivers / stlink_usb.c
index 3b262f9310a475b1eb3e98a20b2abc025ee8ae1c..64868ea9e3d2eed26775196d85f20f93c730feda 100644 (file)
@@ -1,7 +1,10 @@
 /***************************************************************************
- *   Copyright (C) 2011 by Mathias Kuester                                 *
+ *   Copyright (C) 2011-2012 by Mathias Kuester                            *
  *   Mathias Kuester <kesmtp@freenet.de>                                   *
  *                                                                         *
+ *   Copyright (C) 2012 by Spencer Oliver                                  *
+ *   spen@spen-soft.co.uk                                                  *
+ *                                                                         *
  *   This code is based on https://github.com/texane/stlink                *
  *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
@@ -15,9 +18,7 @@
  *   GNU General Public License for more details.                          *
  *                                                                         *
  *   You should have received a copy of the GNU General Public License     *
- *   along with this program; if not, write to the                         *
- *   Free Software Foundation, Inc.,                                       *
- *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
+ *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  ***************************************************************************/
 
 #ifdef HAVE_CONFIG_H
 /* project specific includes */
 #include <helper/binarybuffer.h>
 #include <jtag/interface.h>
-#include <jtag/stlink/stlink_layout.h>
-#include <jtag/stlink/stlink_interface.h>
+#include <jtag/hla/hla_layout.h>
+#include <jtag/hla/hla_transport.h>
+#include <jtag/hla/hla_interface.h>
 #include <target/target.h>
 
+#include <target/cortex_m.h>
+
 #include "libusb_common.h"
 
-#define ENDPOINT_IN    0x80
-#define ENDPOINT_OUT   0x00
+#define ENDPOINT_IN  0x80
+#define ENDPOINT_OUT 0x00
+
+#define STLINK_WRITE_TIMEOUT 1000
+#define STLINK_READ_TIMEOUT 1000
+
+#define STLINK_NULL_EP        0
+#define STLINK_RX_EP          (1|ENDPOINT_IN)
+#define STLINK_TX_EP          (2|ENDPOINT_OUT)
+#define STLINK_TRACE_EP       (3|ENDPOINT_IN)
+
+#define STLINK_V2_1_TX_EP     (1|ENDPOINT_OUT)
+#define STLINK_V2_1_TRACE_EP  (2|ENDPOINT_IN)
+
+#define STLINK_SG_SIZE        (31)
+#define STLINK_DATA_SIZE      (4096)
+#define STLINK_CMD_SIZE_V2    (16)
+#define STLINK_CMD_SIZE_V1    (10)
+
+#define STLINK_V1_PID         (0x3744)
+#define STLINK_V2_PID         (0x3748)
+#define STLINK_V2_1_PID       (0x374B)
 
-#define STLINK_RX_EP   (1|ENDPOINT_IN)
-#define STLINK_TX_EP   (2|ENDPOINT_OUT)
-#define STLINK_CMD_SIZE        (16)
-#define STLINK_TX_SIZE (4*128)
-#define STLINK_RX_SIZE (4*128)
+/* the current implementation of the stlink limits
+ * 8bit read/writes to max 64 bytes. */
+#define STLINK_MAX_RW8         (64)
+
+/* "WAIT" responses will be retried (with exponential backoff) at
+ * most this many times before failing to caller.
+ */
+#define MAX_WAIT_RETRIES 8
+
+enum stlink_jtag_api_version {
+       STLINK_JTAG_API_V1 = 1,
+       STLINK_JTAG_API_V2,
+};
+
+/** */
+struct stlink_usb_version {
+       /** */
+       int stlink;
+       /** */
+       int jtag;
+       /** */
+       int swim;
+       /** highest supported jtag api version */
+       enum stlink_jtag_api_version jtag_api_max;
+};
 
 /** */
 struct stlink_usb_handle_s {
@@ -49,216 +93,664 @@ struct stlink_usb_handle_s {
        /** */
        struct libusb_transfer *trans;
        /** */
-       uint8_t txbuf[STLINK_TX_SIZE];
+       uint8_t rx_ep;
+       /** */
+       uint8_t tx_ep;
+       /** */
+       uint8_t trace_ep;
+       /** */
+       uint8_t cmdbuf[STLINK_SG_SIZE];
+       /** */
+       uint8_t cmdidx;
+       /** */
+       uint8_t direction;
+       /** */
+       uint8_t databuf[STLINK_DATA_SIZE];
+       /** */
+       uint32_t max_mem_packet;
+       /** */
+       enum hl_transports transport;
+       /** */
+       struct stlink_usb_version version;
+       /** */
+       uint16_t vid;
+       /** */
+       uint16_t pid;
+       /** this is the currently used jtag api */
+       enum stlink_jtag_api_version jtag_api;
        /** */
-       uint8_t rxbuf[STLINK_RX_SIZE];
+       struct {
+               /** whether SWO tracing is enabled or not */
+               bool enabled;
+               /** trace module source clock */
+               uint32_t source_hz;
+       } trace;
+       /** reconnect is needed next time we try to query the
+        * status */
+       bool reconnect_pending;
 };
 
-#define STLINK_OK                      0x80
-#define STLINK_FALSE                   0x81
-#define STLINK_CORE_RUNNING            0x80
-#define STLINK_CORE_HALTED             0x81
-#define STLINK_CORE_STAT_UNKNOWN       -1
-
-#define STLINK_GET_VERSION             0xf1
-#define STLINK_GET_CURRENT_MODE                0xf5
-
-#define STLINK_DEBUG_COMMAND           0xF2
-#define STLINK_DFU_COMMAND             0xF3
-#define STLINK_DFU_EXIT                        0x07
-
-#define STLINK_DEV_DFU_MODE            0x00
-#define STLINK_DEV_MASS_MODE           0x01
-#define STLINK_DEV_DEBUG_MODE          0x02
-#define STLINK_DEV_UNKNOWN_MODE                -1
-
-#define STLINK_DEBUG_ENTER             0x20
-#define STLINK_DEBUG_EXIT              0x21
-#define STLINK_DEBUG_READCOREID                0x22
-
-#define STLINK_DEBUG_GETSTATUS         0x01
-#define STLINK_DEBUG_FORCEDEBUG                0x02
-#define STLINK_DEBUG_RESETSYS          0x03
-#define STLINK_DEBUG_READALLREGS       0x04
-#define STLINK_DEBUG_READREG           0x05
-#define STLINK_DEBUG_WRITEREG          0x06
-#define STLINK_DEBUG_READMEM_32BIT     0x07
-#define STLINK_DEBUG_WRITEMEM_32BIT    0x08
-#define STLINK_DEBUG_RUNCORE           0x09
-#define STLINK_DEBUG_STEPCORE          0x0a
-#define STLINK_DEBUG_SETFP             0x0b
-#define STLINK_DEBUG_WRITEMEM_8BIT     0x0d
-#define STLINK_DEBUG_CLEARFP           0x0e
-#define STLINK_DEBUG_WRITEDEBUGREG     0x0f
-#define STLINK_DEBUG_ENTER_SWD         0xa3
-#define STLINK_DEBUG_ENTER_JTAG                0x00
-
-#define STLINK_SWD_ENTER               0x30
-#define STLINK_SWD_READCOREID          0x32
-
-/** */
-int stlink_usb_recv(void *handle, uint8_t *txbuf, int txsize, uint8_t *rxbuf,
-                   int rxsize)
+#define STLINK_DEBUG_ERR_OK            0x80
+#define STLINK_DEBUG_ERR_FAULT         0x81
+#define STLINK_SWD_AP_WAIT             0x10
+#define STLINK_SWD_AP_FAULT            0x11
+#define STLINK_SWD_AP_ERROR            0x12
+#define STLINK_SWD_AP_PARITY_ERROR     0x13
+#define STLINK_JTAG_WRITE_ERROR        0x0c
+#define STLINK_JTAG_WRITE_VERIF_ERROR  0x0d
+#define STLINK_SWD_DP_WAIT             0x14
+#define STLINK_SWD_DP_FAULT            0x15
+#define STLINK_SWD_DP_ERROR            0x16
+#define STLINK_SWD_DP_PARITY_ERROR     0x17
+
+#define STLINK_SWD_AP_WDATA_ERROR      0x18
+#define STLINK_SWD_AP_STICKY_ERROR     0x19
+#define STLINK_SWD_AP_STICKYORUN_ERROR 0x1a
+
+#define STLINK_CORE_RUNNING            0x80
+#define STLINK_CORE_HALTED             0x81
+#define STLINK_CORE_STAT_UNKNOWN       -1
+
+#define STLINK_GET_VERSION             0xF1
+#define STLINK_DEBUG_COMMAND           0xF2
+#define STLINK_DFU_COMMAND             0xF3
+#define STLINK_SWIM_COMMAND            0xF4
+#define STLINK_GET_CURRENT_MODE        0xF5
+#define STLINK_GET_TARGET_VOLTAGE      0xF7
+
+#define STLINK_DEV_DFU_MODE            0x00
+#define STLINK_DEV_MASS_MODE           0x01
+#define STLINK_DEV_DEBUG_MODE          0x02
+#define STLINK_DEV_SWIM_MODE           0x03
+#define STLINK_DEV_BOOTLOADER_MODE     0x04
+#define STLINK_DEV_UNKNOWN_MODE        -1
+
+#define STLINK_DFU_EXIT                0x07
+
+#define STLINK_SWIM_ENTER              0x00
+#define STLINK_SWIM_EXIT               0x01
+
+#define STLINK_DEBUG_ENTER_JTAG            0x00
+#define STLINK_DEBUG_GETSTATUS             0x01
+#define STLINK_DEBUG_FORCEDEBUG            0x02
+#define STLINK_DEBUG_APIV1_RESETSYS        0x03
+#define STLINK_DEBUG_APIV1_READALLREGS     0x04
+#define STLINK_DEBUG_APIV1_READREG         0x05
+#define STLINK_DEBUG_APIV1_WRITEREG        0x06
+#define STLINK_DEBUG_READMEM_32BIT         0x07
+#define STLINK_DEBUG_WRITEMEM_32BIT        0x08
+#define STLINK_DEBUG_RUNCORE               0x09
+#define STLINK_DEBUG_STEPCORE              0x0a
+#define STLINK_DEBUG_APIV1_SETFP           0x0b
+#define STLINK_DEBUG_READMEM_8BIT          0x0c
+#define STLINK_DEBUG_WRITEMEM_8BIT         0x0d
+#define STLINK_DEBUG_APIV1_CLEARFP         0x0e
+#define STLINK_DEBUG_APIV1_WRITEDEBUGREG   0x0f
+#define STLINK_DEBUG_APIV1_SETWATCHPOINT   0x10
+
+#define STLINK_DEBUG_ENTER_JTAG            0x00
+#define STLINK_DEBUG_ENTER_SWD             0xa3
+
+#define STLINK_DEBUG_APIV1_ENTER           0x20
+#define STLINK_DEBUG_EXIT                  0x21
+#define STLINK_DEBUG_READCOREID            0x22
+
+#define STLINK_DEBUG_APIV2_ENTER           0x30
+#define STLINK_DEBUG_APIV2_READ_IDCODES    0x31
+#define STLINK_DEBUG_APIV2_RESETSYS        0x32
+#define STLINK_DEBUG_APIV2_READREG         0x33
+#define STLINK_DEBUG_APIV2_WRITEREG        0x34
+#define STLINK_DEBUG_APIV2_WRITEDEBUGREG   0x35
+#define STLINK_DEBUG_APIV2_READDEBUGREG    0x36
+
+#define STLINK_DEBUG_APIV2_READALLREGS     0x3A
+#define STLINK_DEBUG_APIV2_GETLASTRWSTATUS 0x3B
+#define STLINK_DEBUG_APIV2_DRIVE_NRST      0x3C
+
+#define STLINK_DEBUG_APIV2_START_TRACE_RX  0x40
+#define STLINK_DEBUG_APIV2_STOP_TRACE_RX   0x41
+#define STLINK_DEBUG_APIV2_GET_TRACE_NB    0x42
+#define STLINK_DEBUG_APIV2_SWD_SET_FREQ    0x43
+
+#define STLINK_DEBUG_APIV2_DRIVE_NRST_LOW   0x00
+#define STLINK_DEBUG_APIV2_DRIVE_NRST_HIGH  0x01
+#define STLINK_DEBUG_APIV2_DRIVE_NRST_PULSE 0x02
+
+#define STLINK_TRACE_SIZE               4096
+#define STLINK_TRACE_MAX_HZ             2000000
+#define STLINK_TRACE_MIN_VERSION        13
+
+/** */
+enum stlink_mode {
+       STLINK_MODE_UNKNOWN = 0,
+       STLINK_MODE_DFU,
+       STLINK_MODE_MASS,
+       STLINK_MODE_DEBUG_JTAG,
+       STLINK_MODE_DEBUG_SWD,
+       STLINK_MODE_DEBUG_SWIM
+};
+
+#define REQUEST_SENSE        0x03
+#define REQUEST_SENSE_LENGTH 18
+
+static const struct {
+       int speed;
+       int speed_divisor;
+} stlink_khz_to_speed_map[] = {
+       {4000, 0},
+       {1800, 1}, /* default */
+       {1200, 2},
+       {950,  3},
+       {480,  7},
+       {240, 15},
+       {125, 31},
+       {100, 40},
+       {50,  79},
+       {25, 158},
+       {15, 265},
+       {5,  798}
+};
+
+static void stlink_usb_init_buffer(void *handle, uint8_t direction, uint32_t size);
+
+/** */
+static int stlink_usb_xfer_v1_get_status(void *handle)
 {
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       /* read status */
+       memset(h->cmdbuf, 0, STLINK_SG_SIZE);
+
+       if (jtag_libusb_bulk_read(h->fd, h->rx_ep, (char *)h->cmdbuf,
+                       13, STLINK_READ_TIMEOUT) != 13)
+               return ERROR_FAIL;
+
+       uint32_t t1;
+
+       t1 = buf_get_u32(h->cmdbuf, 0, 32);
 
-       if (jtag_libusb_bulk_write(h->fd, STLINK_TX_EP, (char *)txbuf, txsize,
-                                  1000) != txsize) {
+       /* check for USBS */
+       if (t1 != 0x53425355)
+               return ERROR_FAIL;
+       /*
+        * CSW status:
+        * 0 success
+        * 1 command failure
+        * 2 phase error
+        */
+       if (h->cmdbuf[12] != 0)
+               return ERROR_FAIL;
+
+       return ERROR_OK;
+}
+
+/** */
+static int stlink_usb_xfer_rw(void *handle, int cmdsize, const uint8_t *buf, int size)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       if (jtag_libusb_bulk_write(h->fd, h->tx_ep, (char *)h->cmdbuf, cmdsize,
+                       STLINK_WRITE_TIMEOUT) != cmdsize) {
                return ERROR_FAIL;
        }
-       if (rxsize && rxbuf) {
-               if (jtag_libusb_bulk_read(h->fd, STLINK_RX_EP, (char *)rxbuf,
-                                         rxsize, 1000) != rxsize) {
+
+       if (h->direction == h->tx_ep && size) {
+               if (jtag_libusb_bulk_write(h->fd, h->tx_ep, (char *)buf,
+                               size, STLINK_WRITE_TIMEOUT) != size) {
+                       LOG_DEBUG("bulk write failed");
+                       return ERROR_FAIL;
+               }
+       } else if (h->direction == h->rx_ep && size) {
+               if (jtag_libusb_bulk_read(h->fd, h->rx_ep, (char *)buf,
+                               size, STLINK_READ_TIMEOUT) != size) {
+                       LOG_DEBUG("bulk read failed");
                        return ERROR_FAIL;
                }
        }
+
        return ERROR_OK;
 }
 
 /** */
-void stlink_usb_init_buffer(void *handle)
+static int stlink_usb_xfer_v1_get_sense(void *handle)
 {
-       struct stlink_usb_handle_s *h;
+       int res;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       stlink_usb_init_buffer(handle, h->rx_ep, 16);
+
+       h->cmdbuf[h->cmdidx++] = REQUEST_SENSE;
+       h->cmdbuf[h->cmdidx++] = 0;
+       h->cmdbuf[h->cmdidx++] = 0;
+       h->cmdbuf[h->cmdidx++] = 0;
+       h->cmdbuf[h->cmdidx++] = REQUEST_SENSE_LENGTH;
+
+       res = stlink_usb_xfer_rw(handle, REQUEST_SENSE_LENGTH, h->databuf, 16);
+
+       if (res != ERROR_OK)
+               return res;
+
+       if (stlink_usb_xfer_v1_get_status(handle) != ERROR_OK)
+               return ERROR_FAIL;
 
-       memset(h->txbuf, 0, STLINK_CMD_SIZE);
+       return ERROR_OK;
 }
 
 /** */
-int stlink_usb_version(void *handle)
+static int stlink_usb_xfer(void *handle, const uint8_t *buf, int size)
 {
-       int res;
-       uint16_t v;
-       struct stlink_usb_handle_s *h;
+       int err, cmdsize = STLINK_CMD_SIZE_V2;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->version.stlink == 1)
+               cmdsize = STLINK_SG_SIZE;
 
-       stlink_usb_init_buffer(handle);
+       err = stlink_usb_xfer_rw(handle, cmdsize, buf, size);
 
-       h->txbuf[0] = STLINK_GET_VERSION;
+       if (err != ERROR_OK)
+               return err;
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 6);
+       if (h->version.stlink == 1) {
+               if (stlink_usb_xfer_v1_get_status(handle) != ERROR_OK) {
+                       /* check csw status */
+                       if (h->cmdbuf[12] == 1) {
+                               LOG_DEBUG("get sense");
+                               if (stlink_usb_xfer_v1_get_sense(handle) != ERROR_OK)
+                                       return ERROR_FAIL;
+                       }
+                       return ERROR_FAIL;
+               }
+       }
 
-       if (res != ERROR_OK)
+       return ERROR_OK;
+}
+
+
+/**
+    Converts an STLINK status code held in the first byte of a response
+    to an openocd error, logs any error/wait status as debug output.
+*/
+static int stlink_usb_error_check(void *handle)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       /* TODO: no error checking yet on api V1 */
+       if (h->jtag_api == STLINK_JTAG_API_V1)
+               h->databuf[0] = STLINK_DEBUG_ERR_OK;
+
+       switch (h->databuf[0]) {
+               case STLINK_DEBUG_ERR_OK:
+                       return ERROR_OK;
+               case STLINK_DEBUG_ERR_FAULT:
+                       LOG_DEBUG("SWD fault response (0x%x)", STLINK_DEBUG_ERR_FAULT);
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_WAIT:
+                       LOG_DEBUG("wait status SWD_AP_WAIT (0x%x)", STLINK_SWD_AP_WAIT);
+                       return ERROR_WAIT;
+               case STLINK_SWD_DP_WAIT:
+                       LOG_DEBUG("wait status SWD_DP_WAIT (0x%x)", STLINK_SWD_DP_WAIT);
+                       return ERROR_WAIT;
+               case STLINK_JTAG_WRITE_ERROR:
+                       LOG_DEBUG("Write error");
+                       return ERROR_FAIL;
+               case STLINK_JTAG_WRITE_VERIF_ERROR:
+                       LOG_DEBUG("Verify error");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_FAULT:
+                       /* git://git.ac6.fr/openocd commit 657e3e885b9ee10
+                        * returns ERROR_OK with the comment:
+                        * Change in error status when reading outside RAM.
+                        * This fix allows CDT plugin to visualize memory.
+                        */
+                       LOG_DEBUG("STLINK_SWD_AP_FAULT");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_PARITY_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_PARITY_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_DP_FAULT:
+                       LOG_DEBUG("STLINK_SWD_DP_FAULT");
+                       return ERROR_FAIL;
+               case STLINK_SWD_DP_ERROR:
+                       LOG_DEBUG("STLINK_SWD_DP_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_DP_PARITY_ERROR:
+                       LOG_DEBUG("STLINK_SWD_DP_PARITY_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_WDATA_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_WDATA_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_STICKY_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_STICKY_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_STICKYORUN_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_STICKYORUN_ERROR");
+                       return ERROR_FAIL;
+               default:
+                       LOG_DEBUG("unknown/unexpected STLINK status code 0x%x", h->databuf[0]);
+                       return ERROR_FAIL;
+       }
+}
+
+
+/** Issue an STLINK command via USB transfer, with retries on any wait status responses.
+
+    Works for commands where the STLINK_DEBUG status is returned in the first
+    byte of the response packet.
+
+    Returns an openocd result code.
+*/
+static int stlink_cmd_allow_retry(void *handle, const uint8_t *buf, int size)
+{
+       int retries = 0;
+       int res;
+       while (1) {
+               res = stlink_usb_xfer(handle, buf, size);
+               if (res != ERROR_OK)
+                       return res;
+               res = stlink_usb_error_check(handle);
+               if (res == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                       usleep((1<<retries++) * 1000);
+                       continue;
+               }
                return res;
+       }
+}
 
-       v = (h->rxbuf[0] << 8) | h->rxbuf[1];
+/** */
+static int stlink_usb_read_trace(void *handle, const uint8_t *buf, int size)
+{
+       struct stlink_usb_handle_s *h = handle;
 
-       LOG_DEBUG("STLINK v%d", (v >> 12) & 0x0f);
-       LOG_DEBUG("JTAG   v%d", (v >> 6) & 0x3f);
-       LOG_DEBUG("SWIM   v%d", v & 0x3f);
-       LOG_DEBUG("VID    %04X", buf_get_u32(h->rxbuf, 16, 16));
-       LOG_DEBUG("PID    %04X", buf_get_u32(h->rxbuf, 32, 16));
+       assert(handle != NULL);
+
+       assert(h->version.stlink >= 2);
+
+       if (jtag_libusb_bulk_read(h->fd, h->trace_ep, (char *)buf,
+                       size, STLINK_READ_TIMEOUT) != size) {
+               LOG_ERROR("bulk trace read failed");
+               return ERROR_FAIL;
+       }
 
        return ERROR_OK;
 }
 
 /** */
-int stlink_usb_current_mode(void *handle, uint8_t *mode)
+static void stlink_usb_xfer_v1_create_cmd(void *handle, uint8_t direction, uint32_t size)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       /* fill the send buffer */
+       strcpy((char *)h->cmdbuf, "USBC");
+       h->cmdidx += 4;
+       /* csw tag not used */
+       h->cmdidx += 4;
+       buf_set_u32(h->cmdbuf+h->cmdidx, 0, 32, size);
+       h->cmdidx += 4;
+       h->cmdbuf[h->cmdidx++] = (direction == h->rx_ep ? ENDPOINT_IN : ENDPOINT_OUT);
+       h->cmdbuf[h->cmdidx++] = 0; /* lun */
+       h->cmdbuf[h->cmdidx++] = STLINK_CMD_SIZE_V1;
+}
+
+/** */
+static void stlink_usb_init_buffer(void *handle, uint8_t direction, uint32_t size)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       h->direction = direction;
+
+       h->cmdidx = 0;
+
+       memset(h->cmdbuf, 0, STLINK_SG_SIZE);
+       memset(h->databuf, 0, STLINK_DATA_SIZE);
+
+       if (h->version.stlink == 1)
+               stlink_usb_xfer_v1_create_cmd(handle, direction, size);
+}
+
+/** */
+static int stlink_usb_version(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       uint16_t v;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle);
+       stlink_usb_init_buffer(handle, h->rx_ep, 6);
 
-       h->txbuf[0] = STLINK_GET_CURRENT_MODE;
+       h->cmdbuf[h->cmdidx++] = STLINK_GET_VERSION;
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 2);
+       res = stlink_usb_xfer(handle, h->databuf, 6);
 
        if (res != ERROR_OK)
                return res;
 
-       *mode = h->rxbuf[0];
+       v = (h->databuf[0] << 8) | h->databuf[1];
+
+       h->version.stlink = (v >> 12) & 0x0f;
+       h->version.jtag = (v >> 6) & 0x3f;
+       h->version.swim = v & 0x3f;
+       h->vid = buf_get_u32(h->databuf, 16, 16);
+       h->pid = buf_get_u32(h->databuf, 32, 16);
+
+       /* set the supported jtag api version
+        * API V2 is supported since JTAG V11
+        */
+       if (h->version.jtag >= 11)
+               h->version.jtag_api_max = STLINK_JTAG_API_V2;
+       else
+               h->version.jtag_api_max = STLINK_JTAG_API_V1;
+
+       LOG_INFO("STLINK v%d JTAG v%d API v%d SWIM v%d VID 0x%04X PID 0x%04X",
+               h->version.stlink,
+               h->version.jtag,
+               (h->version.jtag_api_max == STLINK_JTAG_API_V1) ? 1 : 2,
+               h->version.swim,
+               h->vid,
+               h->pid);
 
        return ERROR_OK;
 }
 
-/** */
-int stlink_usb_dfu_mode_leave(void *handle)
+static int stlink_usb_check_voltage(void *handle, float *target_voltage)
 {
-       int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
+       uint32_t adc_results[2];
+
+       /* only supported by stlink/v2 and for firmware >= 13 */
+       if (h->version.stlink == 1 || h->version.jtag < 13)
+               return ERROR_COMMAND_NOTFOUND;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 8);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_GET_TARGET_VOLTAGE;
+
+       int result = stlink_usb_xfer(handle, h->databuf, 8);
+
+       if (result != ERROR_OK)
+               return result;
+
+       /* convert result */
+       adc_results[0] = le_to_h_u32(h->databuf);
+       adc_results[1] = le_to_h_u32(h->databuf + 4);
+
+       *target_voltage = 0;
+
+       if (adc_results[0])
+               *target_voltage = 2 * ((float)adc_results[1]) * (float)(1.2 / adc_results[0]);
+
+       LOG_INFO("Target voltage: %f", (double)*target_voltage);
+
+       return ERROR_OK;
+}
+
+static int stlink_usb_set_swdclk(void *handle, uint16_t clk_divisor)
+{
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       /* only supported by stlink/v2 and for firmware >= 22 */
+       if (h->version.stlink == 1 || h->version.jtag < 22)
+               return ERROR_COMMAND_NOTFOUND;
 
-       stlink_usb_init_buffer(handle);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
-       h->txbuf[0] = STLINK_DFU_COMMAND;
-       h->txbuf[1] = STLINK_DFU_EXIT;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_SWD_SET_FREQ;
+       h_u16_to_le(h->cmdbuf+h->cmdidx, clk_divisor);
+       h->cmdidx += 2;
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, 0, 0);
+       int result = stlink_cmd_allow_retry(handle, h->databuf, 2);
 
-       if (res != ERROR_OK)
-               return res;
+       if (result != ERROR_OK)
+               return result;
 
        return ERROR_OK;
 }
 
 /** */
-int stlink_usb_swd_mode_enter(void *handle)
+static int stlink_usb_current_mode(void *handle, uint8_t *mode)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
-       stlink_usb_init_buffer(handle);
+       h->cmdbuf[h->cmdidx++] = STLINK_GET_CURRENT_MODE;
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_ENTER;
-       h->txbuf[2] = STLINK_DEBUG_ENTER_SWD;
+       res = stlink_usb_xfer(handle, h->databuf, 2);
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, 0, 0);
        if (res != ERROR_OK)
                return res;
 
+       *mode = h->databuf[0];
+
        return ERROR_OK;
 }
 
 /** */
-int stlink_usb_debug_mode_leave(void *handle)
+static int stlink_usb_mode_enter(void *handle, enum stlink_mode type)
 {
-       int res;
-       struct stlink_usb_handle_s *h;
+       int rx_size = 0;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       /* on api V2 we are able the read the latest command
+        * status
+        * TODO: we need the test on api V1 too
+        */
+       if (h->jtag_api == STLINK_JTAG_API_V2)
+               rx_size = 2;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, rx_size);
+
+       switch (type) {
+               case STLINK_MODE_DEBUG_JTAG:
+                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+                       if (h->jtag_api == STLINK_JTAG_API_V1)
+                               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_ENTER;
+                       else
+                               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_ENTER;
+                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_ENTER_JTAG;
+                       break;
+               case STLINK_MODE_DEBUG_SWD:
+                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+                       if (h->jtag_api == STLINK_JTAG_API_V1)
+                               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_ENTER;
+                       else
+                               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_ENTER;
+                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_ENTER_SWD;
+                       break;
+               case STLINK_MODE_DEBUG_SWIM:
+                       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+                       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_ENTER;
+                       break;
+               case STLINK_MODE_DFU:
+               case STLINK_MODE_MASS:
+               default:
+                       return ERROR_FAIL;
+       }
+
+       return stlink_cmd_allow_retry(handle, h->databuf, rx_size);
+}
+
+/** */
+static int stlink_usb_mode_leave(void *handle, enum stlink_mode type)
+{
+       int res;
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
 
-       stlink_usb_init_buffer(handle);
+       stlink_usb_init_buffer(handle, STLINK_NULL_EP, 0);
+
+       switch (type) {
+               case STLINK_MODE_DEBUG_JTAG:
+               case STLINK_MODE_DEBUG_SWD:
+                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_EXIT;
+                       break;
+               case STLINK_MODE_DEBUG_SWIM:
+                       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+                       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_EXIT;
+                       break;
+               case STLINK_MODE_DFU:
+                       h->cmdbuf[h->cmdidx++] = STLINK_DFU_COMMAND;
+                       h->cmdbuf[h->cmdidx++] = STLINK_DFU_EXIT;
+                       break;
+               case STLINK_MODE_MASS:
+               default:
+                       return ERROR_FAIL;
+       }
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_EXIT;
+       res = stlink_usb_xfer(handle, 0, 0);
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, 0, 0);
        if (res != ERROR_OK)
                return res;
 
        return ERROR_OK;
 }
 
+static int stlink_usb_assert_srst(void *handle, int srst);
+
+static enum stlink_mode stlink_get_mode(enum hl_transports t)
+{
+       switch (t) {
+       case HL_TRANSPORT_SWD:
+               return STLINK_MODE_DEBUG_SWD;
+       case HL_TRANSPORT_JTAG:
+               return STLINK_MODE_DEBUG_JTAG;
+       case HL_TRANSPORT_SWIM:
+               return STLINK_MODE_DEBUG_SWIM;
+       default:
+               return STLINK_MODE_UNKNOWN;
+       }
+}
+
 /** */
-int stlink_usb_init_mode(void *handle)
+static int stlink_usb_init_mode(void *handle, bool connect_under_reset)
 {
        int res;
        uint8_t mode;
+       enum stlink_mode emode;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
@@ -267,10 +759,28 @@ int stlink_usb_init_mode(void *handle)
        if (res != ERROR_OK)
                return res;
 
-       LOG_DEBUG("MODE: %02X", mode);
+       LOG_DEBUG("MODE: 0x%02X", mode);
+
+       /* try to exit current mode */
+       switch (mode) {
+               case STLINK_DEV_DFU_MODE:
+                       emode = STLINK_MODE_DFU;
+                       break;
+               case STLINK_DEV_DEBUG_MODE:
+                       emode = STLINK_MODE_DEBUG_SWD;
+                       break;
+               case STLINK_DEV_SWIM_MODE:
+                       emode = STLINK_MODE_DEBUG_SWIM;
+                       break;
+               case STLINK_DEV_BOOTLOADER_MODE:
+               case STLINK_DEV_MASS_MODE:
+               default:
+                       emode = STLINK_MODE_UNKNOWN;
+                       break;
+       }
 
-       if (mode == STLINK_DEV_DFU_MODE) {
-               res = stlink_usb_dfu_mode_leave(handle);
+       if (emode != STLINK_MODE_UNKNOWN) {
+               res = stlink_usb_mode_leave(handle, emode);
 
                if (res != ERROR_OK)
                        return res;
@@ -281,144 +791,408 @@ int stlink_usb_init_mode(void *handle)
        if (res != ERROR_OK)
                return res;
 
-       LOG_DEBUG("MODE: %02X", mode);
+       /* we check the target voltage here as an aid to debugging connection problems.
+        * the stlink requires the target Vdd to be connected for reliable debugging.
+        * this cmd is supported in all modes except DFU
+        */
+       if (mode != STLINK_DEV_DFU_MODE) {
+
+               float target_voltage;
+
+               /* check target voltage (if supported) */
+               res = stlink_usb_check_voltage(h, &target_voltage);
+
+               if (res != ERROR_OK) {
+                       if (res != ERROR_COMMAND_NOTFOUND)
+                               LOG_ERROR("voltage check failed");
+                       /* attempt to continue as it is not a catastrophic failure */
+               } else {
+                       /* check for a sensible target voltage, operating range is 1.65-5.5v
+                        * according to datasheet */
+                       if (target_voltage < 1.5)
+                               LOG_ERROR("target voltage may be too low for reliable debugging");
+               }
+       }
+
+       LOG_DEBUG("MODE: 0x%02X", mode);
 
-       if (mode != STLINK_DEV_DEBUG_MODE) {
-               res = stlink_usb_swd_mode_enter(handle);
+       /* set selected mode */
+       emode = stlink_get_mode(h->transport);
 
+       if (emode == STLINK_MODE_UNKNOWN) {
+               LOG_ERROR("selected mode (transport) not supported");
+               return ERROR_FAIL;
+       }
+
+       if (connect_under_reset) {
+               res = stlink_usb_assert_srst(handle, 0);
                if (res != ERROR_OK)
                        return res;
        }
 
+       res = stlink_usb_mode_enter(handle, emode);
+
+       if (res != ERROR_OK)
+               return res;
+
        res = stlink_usb_current_mode(handle, &mode);
 
        if (res != ERROR_OK)
                return res;
 
-       LOG_DEBUG("MODE: %02X", mode);
+       LOG_DEBUG("MODE: 0x%02X", mode);
 
        return ERROR_OK;
 }
 
 /** */
-int stlink_usb_idcode(void *handle, uint32_t *idcode)
+static int stlink_usb_idcode(void *handle, uint32_t *idcode)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       stlink_usb_init_buffer(handle, h->rx_ep, 4);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_READCOREID;
+
+       res = stlink_usb_xfer(handle, h->databuf, 4);
 
-       stlink_usb_init_buffer(handle);
+       if (res != ERROR_OK)
+               return res;
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_READCOREID;
+       *idcode = le_to_h_u32(h->databuf);
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 4);
+       LOG_DEBUG("IDCODE: 0x%08" PRIX32, *idcode);
 
+       return ERROR_OK;
+}
+
+static int stlink_usb_v2_read_debug_reg(void *handle, uint32_t addr, uint32_t *val)
+{
+       struct stlink_usb_handle_s *h = handle;
+       int res;
+
+       assert(handle != NULL);
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 8);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_READDEBUGREG;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+
+       res = stlink_cmd_allow_retry(handle, h->databuf, 8);
        if (res != ERROR_OK)
                return res;
 
-       *idcode = le_to_h_u32(h->rxbuf);
+       *val = le_to_h_u32(h->databuf + 4);
+       return ERROR_OK;
+}
+
+static int stlink_usb_write_debug_reg(void *handle, uint32_t addr, uint32_t val)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       if (h->jtag_api == STLINK_JTAG_API_V1)
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_WRITEDEBUGREG;
+       else
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_WRITEDEBUGREG;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, val);
+       h->cmdidx += 4;
+
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
+}
+
+/** */
+static int stlink_usb_trace_read(void *handle, uint8_t *buf, size_t *size)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       if (h->trace.enabled && h->version.jtag >= STLINK_TRACE_MIN_VERSION) {
+               int res;
+
+               stlink_usb_init_buffer(handle, h->rx_ep, 10);
 
-       LOG_DEBUG("IDCODE: %08X", *idcode);
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_GET_TRACE_NB;
 
+               res = stlink_usb_xfer(handle, h->databuf, 2);
+               if (res != ERROR_OK)
+                       return res;
+
+               size_t bytes_avail = le_to_h_u16(h->databuf);
+               *size = bytes_avail < *size ? bytes_avail : *size - 1;
+
+               if (*size > 0) {
+                       res = stlink_usb_read_trace(handle, buf, *size);
+                       if (res != ERROR_OK)
+                               return res;
+                       return ERROR_OK;
+               }
+       }
+       *size = 0;
        return ERROR_OK;
 }
 
+static enum target_state stlink_usb_v2_get_status(void *handle)
+{
+       int result;
+       uint32_t status;
+
+       result = stlink_usb_v2_read_debug_reg(handle, DCB_DHCSR, &status);
+       if  (result != ERROR_OK)
+               return TARGET_UNKNOWN;
+
+       if (status & S_HALT)
+               return TARGET_HALTED;
+       else if (status & S_RESET_ST)
+               return TARGET_RESET;
+
+       return TARGET_RUNNING;
+}
+
 /** */
-enum target_state stlink_usb_state(void *handle)
+static enum target_state stlink_usb_state(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->reconnect_pending) {
+               LOG_INFO("Previous state query failed, trying to reconnect");
+               res = stlink_usb_mode_enter(handle, stlink_get_mode(h->transport));
+
+               if (res != ERROR_OK)
+                       return TARGET_UNKNOWN;
 
-       stlink_usb_init_buffer(handle);
+               h->reconnect_pending = false;
+       }
+
+       if (h->jtag_api == STLINK_JTAG_API_V2) {
+               res = stlink_usb_v2_get_status(handle);
+               if (res == TARGET_UNKNOWN)
+                       h->reconnect_pending = true;
+               return res;
+       }
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_GETSTATUS;
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 2);
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_GETSTATUS;
+
+       res = stlink_usb_xfer(handle, h->databuf, 2);
 
        if (res != ERROR_OK)
                return TARGET_UNKNOWN;
 
-       if (h->rxbuf[0] == STLINK_CORE_RUNNING)
+       if (h->databuf[0] == STLINK_CORE_RUNNING)
                return TARGET_RUNNING;
-       if (h->rxbuf[0] == STLINK_CORE_HALTED)
+       if (h->databuf[0] == STLINK_CORE_HALTED)
                return TARGET_HALTED;
 
+       h->reconnect_pending = true;
+
        return TARGET_UNKNOWN;
 }
 
+static int stlink_usb_assert_srst(void *handle, int srst)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       if (h->version.stlink == 1)
+               return ERROR_COMMAND_NOTFOUND;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_DRIVE_NRST;
+       h->cmdbuf[h->cmdidx++] = srst;
+
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
+}
+
+/** */
+static void stlink_usb_trace_disable(void *handle)
+{
+       int res = ERROR_OK;
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       assert(h->version.jtag >= STLINK_TRACE_MIN_VERSION);
+
+       LOG_DEBUG("Tracing: disable");
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_STOP_TRACE_RX;
+       res = stlink_usb_xfer(handle, h->databuf, 2);
+
+       if (res == ERROR_OK)
+               h->trace.enabled = false;
+}
+
+
 /** */
-int stlink_usb_reset(void *handle)
+static int stlink_usb_trace_enable(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->version.jtag >= STLINK_TRACE_MIN_VERSION) {
+               stlink_usb_init_buffer(handle, h->rx_ep, 10);
 
-       stlink_usb_init_buffer(handle);
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_START_TRACE_RX;
+               h_u16_to_le(h->cmdbuf+h->cmdidx, (uint16_t)STLINK_TRACE_SIZE);
+               h->cmdidx += 2;
+               h_u32_to_le(h->cmdbuf+h->cmdidx, h->trace.source_hz);
+               h->cmdidx += 4;
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_RESETSYS;
+               res = stlink_usb_xfer(handle, h->databuf, 2);
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 2);
+               if (res == ERROR_OK)  {
+                       h->trace.enabled = true;
+                       LOG_DEBUG("Tracing: recording at %" PRIu32 "Hz", h->trace.source_hz);
+               }
+       } else {
+               LOG_ERROR("Tracing is not supported by this version.");
+               res = ERROR_FAIL;
+       }
 
-       if (res != ERROR_OK)
-               return res;
+       return res;
+}
+
+/** */
+static int stlink_usb_reset(void *handle)
+{
+       struct stlink_usb_handle_s *h = handle;
+       int retval;
+
+       assert(handle != NULL);
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+
+       if (h->jtag_api == STLINK_JTAG_API_V1)
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_RESETSYS;
+       else
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_RESETSYS;
 
-       LOG_DEBUG("RESET: %08X", h->rxbuf[0]);
+       retval = stlink_cmd_allow_retry(handle, h->databuf, 2);
+       if (retval != ERROR_OK)
+               return retval;
+
+       if (h->trace.enabled) {
+               stlink_usb_trace_disable(h);
+               return stlink_usb_trace_enable(h);
+       }
 
        return ERROR_OK;
 }
 
 /** */
-int stlink_usb_run(void *handle)
+static int stlink_usb_run(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->jtag_api == STLINK_JTAG_API_V2) {
+               res = stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_DEBUGEN);
 
-       stlink_usb_init_buffer(handle);
+               return res;
+       }
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_RUNCORE;
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 2);
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_RUNCORE;
+
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
+}
+
+/** */
+static int stlink_usb_halt(void *handle)
+{
+       int res;
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       if (h->jtag_api == STLINK_JTAG_API_V2) {
+               res = stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_HALT|C_DEBUGEN);
 
-       if (res != ERROR_OK)
                return res;
+       }
 
-       return ERROR_OK;
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_FORCEDEBUG;
+
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
 }
 
 /** */
-int stlink_usb_halt(void *handle)
+static int stlink_usb_step(void *handle)
 {
-       int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->jtag_api == STLINK_JTAG_API_V2) {
+               /* TODO: this emulates the v1 api, it should really use a similar auto mask isr
+                * that the Cortex-M3 currently does. */
+               stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_HALT|C_MASKINTS|C_DEBUGEN);
+               stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_STEP|C_MASKINTS|C_DEBUGEN);
+               return stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_HALT|C_DEBUGEN);
+       }
 
-       stlink_usb_init_buffer(handle);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_FORCEDEBUG;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_STEPCORE;
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 2);
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
+}
+
+/** */
+static int stlink_usb_read_regs(void *handle)
+{
+       int res;
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 84);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       if (h->jtag_api == STLINK_JTAG_API_V1)
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_READALLREGS;
+       else
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_READALLREGS;
+
+       res = stlink_usb_xfer(handle, h->databuf, 84);
 
        if (res != ERROR_OK)
                return res;
@@ -427,219 +1201,665 @@ int stlink_usb_halt(void *handle)
 }
 
 /** */
-int stlink_usb_step(void *handle)
+static int stlink_usb_read_reg(void *handle, int num, uint32_t *val)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       stlink_usb_init_buffer(handle, h->rx_ep, h->jtag_api == STLINK_JTAG_API_V1 ? 4 : 8);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       if (h->jtag_api == STLINK_JTAG_API_V1)
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_READREG;
+       else
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_READREG;
+       h->cmdbuf[h->cmdidx++] = num;
+
+       if (h->jtag_api == STLINK_JTAG_API_V1) {
+               res = stlink_usb_xfer(handle, h->databuf, 4);
+               if (res != ERROR_OK)
+                       return res;
+               *val = le_to_h_u32(h->databuf);
+               return ERROR_OK;
+       } else {
+               res = stlink_cmd_allow_retry(handle, h->databuf, 8);
+               if (res != ERROR_OK)
+                       return res;
+               *val = le_to_h_u32(h->databuf + 4);
+               return ERROR_OK;
+       }
+}
 
-       stlink_usb_init_buffer(handle);
+/** */
+static int stlink_usb_write_reg(void *handle, int num, uint32_t val)
+{
+       struct stlink_usb_handle_s *h = handle;
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_STEPCORE;
+       assert(handle != NULL);
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 2);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
-       if (res != ERROR_OK)
-               return res;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       if (h->jtag_api == STLINK_JTAG_API_V1)
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_WRITEREG;
+       else
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_WRITEREG;
+       h->cmdbuf[h->cmdidx++] = num;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, val);
+       h->cmdidx += 4;
 
-       return ERROR_OK;
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
 }
 
-/** */
-int stlink_usb_read_regs(void *handle)
+static int stlink_usb_get_rw_status(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->jtag_api == STLINK_JTAG_API_V1)
+               return ERROR_OK;
 
-       stlink_usb_init_buffer(handle);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_READALLREGS;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_GETLASTRWSTATUS;
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 84);
+       res = stlink_usb_xfer(handle, h->databuf, 2);
 
        if (res != ERROR_OK)
                return res;
 
-       return ERROR_OK;
+       return stlink_usb_error_check(h);
 }
 
 /** */
-int stlink_usb_read_reg(void *handle, int num, uint32_t *val)
+static int stlink_usb_read_mem8(void *handle, uint32_t addr, uint16_t len,
+                         uint8_t *buffer)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       uint16_t read_len = len;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       /* max 8bit read/write is 64bytes */
+       if (len > STLINK_MAX_RW8) {
+               LOG_DEBUG("max buffer length exceeded");
+               return ERROR_FAIL;
+       }
 
-       stlink_usb_init_buffer(handle);
+       stlink_usb_init_buffer(handle, h->rx_ep, read_len);
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_READREG;
-       h->txbuf[2] = num;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_READMEM_8BIT;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+       h_u16_to_le(h->cmdbuf+h->cmdidx, len);
+       h->cmdidx += 2;
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 4);
+       /* we need to fix read length for single bytes */
+       if (read_len == 1)
+               read_len++;
+
+       res = stlink_usb_xfer(handle, h->databuf, read_len);
 
        if (res != ERROR_OK)
                return res;
 
-       *val = le_to_h_u32(h->rxbuf);
+       memcpy(buffer, h->databuf, len);
 
-       return ERROR_OK;
+       return stlink_usb_get_rw_status(handle);
 }
 
 /** */
-int stlink_usb_write_reg(void *handle, int num, uint32_t val)
+static int stlink_usb_write_mem8(void *handle, uint32_t addr, uint16_t len,
+                          const uint8_t *buffer)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       /* max 8bit read/write is 64bytes */
+       if (len > STLINK_MAX_RW8) {
+               LOG_DEBUG("max buffer length exceeded");
+               return ERROR_FAIL;
+       }
 
-       stlink_usb_init_buffer(handle);
+       stlink_usb_init_buffer(handle, h->tx_ep, len);
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_WRITEREG;
-       h->txbuf[2] = num;
-       h_u32_to_le(h->txbuf + 3, val);
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_WRITEMEM_8BIT;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+       h_u16_to_le(h->cmdbuf+h->cmdidx, len);
+       h->cmdidx += 2;
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, 2);
+       res = stlink_usb_xfer(handle, buffer, len);
 
        if (res != ERROR_OK)
                return res;
 
-       return ERROR_OK;
+       return stlink_usb_get_rw_status(handle);
 }
 
 /** */
-int stlink_usb_read_mem32(void *handle, uint32_t addr, uint16_t len,
-                         uint32_t *buffer)
+static int stlink_usb_read_mem32(void *handle, uint32_t addr, uint16_t len,
+                         uint8_t *buffer)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle);
+       /* data must be a multiple of 4 and word aligned */
+       if (len % 4 || addr % 4) {
+               LOG_DEBUG("Invalid data alignment");
+               return ERROR_TARGET_UNALIGNED_ACCESS;
+       }
 
-       len *= 4;
+       stlink_usb_init_buffer(handle, h->rx_ep, len);
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_READMEM_32BIT;
-       h_u32_to_le(h->txbuf + 2, addr);
-       h_u16_to_le(h->txbuf + 2 + 4, len);
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_READMEM_32BIT;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+       h_u16_to_le(h->cmdbuf+h->cmdidx, len);
+       h->cmdidx += 2;
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, h->rxbuf, len);
+       res = stlink_usb_xfer(handle, h->databuf, len);
 
        if (res != ERROR_OK)
                return res;
 
-       memcpy(buffer, h->rxbuf, len);
+       memcpy(buffer, h->databuf, len);
 
-       return ERROR_OK;
+       return stlink_usb_get_rw_status(handle);
 }
 
 /** */
-int stlink_usb_write_mem32(void *handle, uint32_t addr, uint16_t len,
-                          uint32_t *buffer)
+static int stlink_usb_write_mem32(void *handle, uint32_t addr, uint16_t len,
+                          const uint8_t *buffer)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle);
+       /* data must be a multiple of 4 and word aligned */
+       if (len % 4 || addr % 4) {
+               LOG_DEBUG("Invalid data alignment");
+               return ERROR_TARGET_UNALIGNED_ACCESS;
+       }
 
-       len *= 4;
+       stlink_usb_init_buffer(handle, h->tx_ep, len);
 
-       h->txbuf[0] = STLINK_DEBUG_COMMAND;
-       h->txbuf[1] = STLINK_DEBUG_WRITEMEM_32BIT;
-       h_u32_to_le(h->txbuf + 2, addr);
-       h_u16_to_le(h->txbuf + 2 + 4, len);
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_WRITEMEM_32BIT;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+       h_u16_to_le(h->cmdbuf+h->cmdidx, len);
+       h->cmdidx += 2;
 
-       res = stlink_usb_recv(handle, h->txbuf, STLINK_CMD_SIZE, 0, 0);
+       res = stlink_usb_xfer(handle, buffer, len);
 
        if (res != ERROR_OK)
                return res;
 
-       res = stlink_usb_recv(handle, (uint8_t *) buffer, len, 0, 0);
+       return stlink_usb_get_rw_status(handle);
+}
 
-       if (res != ERROR_OK)
-               return res;
+static uint32_t stlink_max_block_size(uint32_t tar_autoincr_block, uint32_t address)
+{
+       uint32_t max_tar_block = (tar_autoincr_block - ((tar_autoincr_block - 1) & address));
+       if (max_tar_block == 0)
+               max_tar_block = 4;
+       return max_tar_block;
+}
+
+static int stlink_usb_read_mem(void *handle, uint32_t addr, uint32_t size,
+               uint32_t count, uint8_t *buffer)
+{
+       int retval = ERROR_OK;
+       uint32_t bytes_remaining;
+       int retries = 0;
+       struct stlink_usb_handle_s *h = handle;
+
+       /* calculate byte count */
+       count *= size;
+
+       while (count) {
+
+               bytes_remaining = (size == 4) ? \
+                               stlink_max_block_size(h->max_mem_packet, addr) : STLINK_MAX_RW8;
+
+               if (count < bytes_remaining)
+                       bytes_remaining = count;
+
+               /* the stlink only supports 8/32bit memory read/writes
+                * honour 32bit, all others will be handled as 8bit access */
+               if (size == 4) {
+
+                       /* When in jtag mode the stlink uses the auto-increment functinality.
+                        * However it expects us to pass the data correctly, this includes
+                        * alignment and any page boundaries. We already do this as part of the
+                        * adi_v5 implementation, but the stlink is a hla adapter and so this
+                        * needs implementiong manually.
+                        * currently this only affects jtag mode, according to ST they do single
+                        * access in SWD mode - but this may change and so we do it for both modes */
+
+                       /* we first need to check for any unaligned bytes */
+                       if (addr % 4) {
+
+                               uint32_t head_bytes = 4 - (addr % 4);
+                               retval = stlink_usb_read_mem8(handle, addr, head_bytes, buffer);
+                               if (retval == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                                       usleep((1<<retries++) * 1000);
+                                       continue;
+                               }
+                               if (retval != ERROR_OK)
+                                       return retval;
+                               buffer += head_bytes;
+                               addr += head_bytes;
+                               count -= head_bytes;
+                               bytes_remaining -= head_bytes;
+                       }
+
+                       if (bytes_remaining % 4)
+                               retval = stlink_usb_read_mem(handle, addr, 1, bytes_remaining, buffer);
+                       else
+                               retval = stlink_usb_read_mem32(handle, addr, bytes_remaining, buffer);
+               } else
+                       retval = stlink_usb_read_mem8(handle, addr, bytes_remaining, buffer);
+
+               if (retval == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                       usleep((1<<retries++) * 1000);
+                       continue;
+               }
+               if (retval != ERROR_OK)
+                       return retval;
 
-       memcpy(buffer, h->rxbuf, len);
+               buffer += bytes_remaining;
+               addr += bytes_remaining;
+               count -= bytes_remaining;
+       }
+
+       return retval;
+}
+
+static int stlink_usb_write_mem(void *handle, uint32_t addr, uint32_t size,
+               uint32_t count, const uint8_t *buffer)
+{
+       int retval = ERROR_OK;
+       uint32_t bytes_remaining;
+       int retries = 0;
+       struct stlink_usb_handle_s *h = handle;
+
+       /* calculate byte count */
+       count *= size;
+
+       while (count) {
+
+               bytes_remaining = (size == 4) ? \
+                               stlink_max_block_size(h->max_mem_packet, addr) : STLINK_MAX_RW8;
+
+               if (count < bytes_remaining)
+                       bytes_remaining = count;
+
+               /* the stlink only supports 8/32bit memory read/writes
+                * honour 32bit, all others will be handled as 8bit access */
+               if (size == 4) {
+
+                       /* When in jtag mode the stlink uses the auto-increment functinality.
+                        * However it expects us to pass the data correctly, this includes
+                        * alignment and any page boundaries. We already do this as part of the
+                        * adi_v5 implementation, but the stlink is a hla adapter and so this
+                        * needs implementiong manually.
+                        * currently this only affects jtag mode, according to ST they do single
+                        * access in SWD mode - but this may change and so we do it for both modes */
+
+                       /* we first need to check for any unaligned bytes */
+                       if (addr % 4) {
+
+                               uint32_t head_bytes = 4 - (addr % 4);
+                               retval = stlink_usb_write_mem8(handle, addr, head_bytes, buffer);
+                               if (retval == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                                       usleep((1<<retries++) * 1000);
+                                       continue;
+                               }
+                               if (retval != ERROR_OK)
+                                       return retval;
+                               buffer += head_bytes;
+                               addr += head_bytes;
+                               count -= head_bytes;
+                               bytes_remaining -= head_bytes;
+                       }
+
+                       if (bytes_remaining % 4)
+                               retval = stlink_usb_write_mem(handle, addr, 1, bytes_remaining, buffer);
+                       else
+                               retval = stlink_usb_write_mem32(handle, addr, bytes_remaining, buffer);
+
+               } else
+                       retval = stlink_usb_write_mem8(handle, addr, bytes_remaining, buffer);
+               if (retval == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                       usleep((1<<retries++) * 1000);
+                       continue;
+               }
+               if (retval != ERROR_OK)
+                       return retval;
+
+               buffer += bytes_remaining;
+               addr += bytes_remaining;
+               count -= bytes_remaining;
+       }
+
+       return retval;
+}
+
+/** */
+static int stlink_usb_override_target(const char *targetname)
+{
+       return !strcmp(targetname, "cortex_m");
+}
+
+static int stlink_speed(void *handle, int khz, bool query)
+{
+       unsigned i;
+       int speed_index = -1;
+       int speed_diff = INT_MAX;
+       struct stlink_usb_handle_s *h = handle;
+
+       /* only supported by stlink/v2 and for firmware >= 22 */
+       if (h && (h->version.stlink == 1 || h->version.jtag < 22))
+               return khz;
+
+       for (i = 0; i < ARRAY_SIZE(stlink_khz_to_speed_map); i++) {
+               if (khz == stlink_khz_to_speed_map[i].speed) {
+                       speed_index = i;
+                       break;
+               } else {
+                       int current_diff = khz - stlink_khz_to_speed_map[i].speed;
+                       /* get abs value for comparison */
+                       current_diff = (current_diff > 0) ? current_diff : -current_diff;
+                       if ((current_diff < speed_diff) && khz >= stlink_khz_to_speed_map[i].speed) {
+                               speed_diff = current_diff;
+                               speed_index = i;
+                       }
+               }
+       }
+
+       bool match = true;
+
+       if (speed_index == -1) {
+               /* this will only be here if we cannot match the slow speed.
+                * use the slowest speed we support.*/
+               speed_index = ARRAY_SIZE(stlink_khz_to_speed_map) - 1;
+               match = false;
+       } else if (i == ARRAY_SIZE(stlink_khz_to_speed_map))
+               match = false;
+
+       if (!match && query) {
+               LOG_INFO("Unable to match requested speed %d kHz, using %d kHz", \
+                               khz, stlink_khz_to_speed_map[speed_index].speed);
+       }
+
+       if (h && !query) {
+               int result = stlink_usb_set_swdclk(h, stlink_khz_to_speed_map[speed_index].speed_divisor);
+               if (result != ERROR_OK) {
+                       LOG_ERROR("Unable to set adapter speed");
+                       return khz;
+               }
+       }
+
+       return stlink_khz_to_speed_map[speed_index].speed;
+}
+
+/** */
+static int stlink_usb_close(void *handle)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       if (h && h->fd)
+               jtag_libusb_close(h->fd);
+
+       free(h);
 
        return ERROR_OK;
 }
 
 /** */
-int stlink_usb_open(struct stlink_interface_param_s *param, void **fd)
+static int stlink_usb_open(struct hl_interface_param_s *param, void **fd)
 {
+       int err, retry_count = 1;
        struct stlink_usb_handle_s *h;
+       enum stlink_jtag_api_version api;
 
        LOG_DEBUG("stlink_usb_open");
 
-       h = malloc(sizeof(struct stlink_usb_handle_s));
+       h = calloc(1, sizeof(struct stlink_usb_handle_s));
 
        if (h == 0) {
-               LOG_DEBUG("stlink_open_usb: malloc failed");
+               LOG_DEBUG("malloc failed");
                return ERROR_FAIL;
        }
 
-       const uint16_t vids[] = { param->vid, 0 };
-       const uint16_t pids[] = { param->pid, 0 };
+       h->transport = param->transport;
 
-       LOG_DEBUG("stlink_open_usb: vid: %04x pid: %04x", param->vid,
-                 param->pid);
+       for (unsigned i = 0; param->vid[i]; i++) {
+               LOG_DEBUG("transport: %d vid: 0x%04x pid: 0x%04x serial: %s",
+                         param->transport, param->vid[i], param->pid[i],
+                         param->serial ? param->serial : "");
+       }
 
-       if (jtag_libusb_open(vids, pids, &h->fd) != ERROR_OK) {
-               LOG_ERROR("stlink_open_usb: open failed");
-               return ERROR_FAIL;
+       /*
+         On certain host USB configurations(e.g. MacBook Air)
+         STLINKv2 dongle seems to have its FW in a funky state if,
+         after plugging it in, you try to use openocd with it more
+         then once (by launching and closing openocd). In cases like
+         that initial attempt to read the FW info via
+         stlink_usb_version will fail and the device has to be reset
+         in order to become operational.
+        */
+       do {
+               if (jtag_libusb_open(param->vid, param->pid, param->serial, &h->fd) != ERROR_OK) {
+                       LOG_ERROR("open failed");
+                       goto error_open;
+               }
+
+               jtag_libusb_set_configuration(h->fd, 0);
+
+               if (jtag_libusb_claim_interface(h->fd, 0) != ERROR_OK) {
+                       LOG_DEBUG("claim interface failed");
+                       goto error_open;
+               }
+
+               /* RX EP is common for all versions */
+               h->rx_ep = STLINK_RX_EP;
+
+               uint16_t pid;
+               if (jtag_libusb_get_pid(jtag_libusb_get_device(h->fd), &pid) != ERROR_OK) {
+                       LOG_DEBUG("libusb_get_pid failed");
+                       goto error_open;
+               }
+
+               /* wrap version for first read */
+               switch (pid) {
+                       case STLINK_V1_PID:
+                               h->version.stlink = 1;
+                               h->tx_ep = STLINK_TX_EP;
+                               h->trace_ep = STLINK_TRACE_EP;
+                               break;
+                       case STLINK_V2_1_PID:
+                               h->version.stlink = 2;
+                               h->tx_ep = STLINK_V2_1_TX_EP;
+                               h->trace_ep = STLINK_V2_1_TRACE_EP;
+                               break;
+                       default:
+                       /* fall through - we assume V2 to be the default version*/
+                       case STLINK_V2_PID:
+                               h->version.stlink = 2;
+                               h->tx_ep = STLINK_TX_EP;
+                               h->trace_ep = STLINK_TRACE_EP;
+                               break;
+               }
+
+               /* get the device version */
+               err = stlink_usb_version(h);
+
+               if (err == ERROR_OK) {
+                       break;
+               } else if (h->version.stlink == 1 ||
+                          retry_count == 0) {
+                       LOG_ERROR("read version failed");
+                       goto error_open;
+               } else {
+                       err = jtag_libusb_release_interface(h->fd, 0);
+                       if (err != ERROR_OK) {
+                               LOG_ERROR("release interface failed");
+                               goto error_open;
+                       }
+
+                       err = jtag_libusb_reset_device(h->fd);
+                       if (err != ERROR_OK) {
+                               LOG_ERROR("reset device failed");
+                               goto error_open;
+                       }
+
+                       jtag_libusb_close(h->fd);
+                       /*
+                         Give the device one second to settle down and
+                         reenumerate.
+                        */
+                       usleep(1 * 1000 * 1000);
+                       retry_count--;
+               }
+       } while (1);
+
+       /* check if mode is supported */
+       err = ERROR_OK;
+
+       switch (h->transport) {
+               case HL_TRANSPORT_SWD:
+               case HL_TRANSPORT_JTAG:
+                       if (h->version.jtag == 0)
+                               err = ERROR_FAIL;
+                       break;
+               case HL_TRANSPORT_SWIM:
+                       if (h->version.swim == 0)
+                               err = ERROR_FAIL;
+                       break;
+               default:
+                       err = ERROR_FAIL;
+                       break;
        }
 
-       jtag_libusb_set_configuration(h->fd, 0);
+       if (err != ERROR_OK) {
+               LOG_ERROR("mode (transport) not supported by device");
+               goto error_open;
+       }
 
-       if (jtag_libusb_claim_interface(h->fd, 0) != ERROR_OK) {
-               LOG_DEBUG("stlink_open_usb: claim failed");
-               return ERROR_FAIL;
+       api = h->version.jtag_api_max;
+
+       LOG_INFO("using stlink api v%d", api);
+
+       /* set the used jtag api, this will default to the newest supported version */
+       h->jtag_api = api;
+
+       /* initialize the debug hardware */
+       err = stlink_usb_init_mode(h, param->connect_under_reset);
+
+       if (err != ERROR_OK) {
+               LOG_ERROR("init mode failed (unable to connect to the target)");
+               goto error_open;
+       }
+
+       /* clock speed only supported by stlink/v2 and for firmware >= 22 */
+       if (h->version.stlink >= 2 && h->version.jtag >= 22) {
+               LOG_DEBUG("Supported clock speeds are:");
+
+               for (unsigned i = 0; i < ARRAY_SIZE(stlink_khz_to_speed_map); i++)
+                       LOG_DEBUG("%d kHz", stlink_khz_to_speed_map[i].speed);
+
+               stlink_speed(h, param->initial_interface_speed, false);
        }
 
-       stlink_usb_init_mode(h);
+       /* get cpuid, so we can determine the max page size
+        * start with a safe default */
+       h->max_mem_packet = (1 << 10);
+
+       uint8_t buffer[4];
+       err = stlink_usb_read_mem32(h, CPUID, 4, buffer);
+       if (err == ERROR_OK) {
+               uint32_t cpuid = le_to_h_u32(buffer);
+               int i = (cpuid >> 4) & 0xf;
+               if (i == 4 || i == 3) {
+                       /* Cortex-M3/M4 has 4096 bytes autoincrement range */
+                       h->max_mem_packet = (1 << 12);
+               }
+       }
 
-       stlink_usb_version(h);
+       LOG_DEBUG("Using TAR autoincrement: %" PRIu32, h->max_mem_packet);
 
        *fd = h;
 
        return ERROR_OK;
+
+error_open:
+       stlink_usb_close(h);
+
+       return ERROR_FAIL;
+}
+
+int stlink_config_trace(void *handle, bool enabled, enum tpio_pin_protocol pin_protocol,
+                       uint32_t port_size, unsigned int *trace_freq)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       if (enabled && (h->jtag_api < 2 || pin_protocol != ASYNC_UART)) {
+               LOG_ERROR("The attached ST-LINK version doesn't support this trace mode");
+               return ERROR_FAIL;
+       }
+
+       if (!enabled) {
+               stlink_usb_trace_disable(h);
+               return ERROR_OK;
+       }
+
+       if (*trace_freq > STLINK_TRACE_MAX_HZ) {
+               LOG_ERROR("ST-LINK doesn't support SWO frequency higher than %u",
+                         STLINK_TRACE_MAX_HZ);
+               return ERROR_FAIL;
+       }
+
+       stlink_usb_trace_disable(h);
+
+       if (!*trace_freq)
+               *trace_freq = STLINK_TRACE_MAX_HZ;
+       h->trace.source_hz = *trace_freq;
+
+       return stlink_usb_trace_enable(h);
 }
 
 /** */
-struct stlink_layout_api_s stlink_layout_api = {
+struct hl_layout_api_s stlink_usb_layout_api = {
        /** */
        .open = stlink_usb_open,
        /** */
+       .close = stlink_usb_close,
+       /** */
        .idcode = stlink_usb_idcode,
        /** */
        .state = stlink_usb_state,
        /** */
        .reset = stlink_usb_reset,
        /** */
+       .assert_srst = stlink_usb_assert_srst,
+       /** */
        .run = stlink_usb_run,
        /** */
        .halt = stlink_usb_halt,
@@ -652,7 +1872,17 @@ struct stlink_layout_api_s stlink_layout_api = {
        /** */
        .write_reg = stlink_usb_write_reg,
        /** */
-       .read_mem32 = stlink_usb_read_mem32,
+       .read_mem = stlink_usb_read_mem,
+       /** */
+       .write_mem = stlink_usb_write_mem,
+       /** */
+       .write_debug_reg = stlink_usb_write_debug_reg,
+       /** */
+       .override_target = stlink_usb_override_target,
+       /** */
+       .speed = stlink_speed,
+       /** */
+       .config_trace = stlink_config_trace,
        /** */
-       .write_mem32 = stlink_usb_write_mem32,
+       .poll_trace = stlink_usb_trace_read,
 };