jlink: improve USB read during jlink_tap_execute

Previously, when doing EMU_CMD_HW_JTAG3 commands we would do two reads,
one to read the data, and one to read the result. However, we can just
do a single larger read instead.

The motivation for this change is a weird problem. If I run the Segger
software before running OpenOCD, then the first read always fails:
Error: usb_bulk_read failed (requested=1, result=0)
Error: jlink_tap_execute, wrong result -107 (expected 1)

Sniffing the USB traffic shows that the J-Link is returning an
overflow error, meaning it is expecting to return the full result
in a single read.

Change-Id: I75e020d3b3732c9a74ee3d31838fdf17a7fac24c
Signed-off-by: Philip Craig <phil@blackmoth.com.au>
Reviewed-on: http://openocd.zylin.com/1447
Tested-by: jenkins
Reviewed-by: Xiaofan <xiaofanc@gmail.com>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

diff --git a/src/jtag/drivers/jlink.c b/src/jtag/drivers/jlink.c
index edf972575ca994692e47277bc5372675c28810d3..ae80eb89b069c721ddab68fc03e0fcc3e9504e0b 100644 (file)
--- a/src/jtag/drivers/jlink.c
+++ b/src/jtag/drivers/jlink.c
@@ -64,14 +64,12 @@ static unsigned int jlink_hw_jtag_version = 2;
 /*#define JLINK_TAP_BUFFER_SIZE 256*/
 /*#define JLINK_TAP_BUFFER_SIZE 384*/
 
-#define JLINK_IN_BUFFER_SIZE                   2048
+#define JLINK_IN_BUFFER_SIZE                   (2048 + 1)
 #define JLINK_OUT_BUFFER_SIZE                  (2*2048 + 4)
-#define JLINK_EMU_RESULT_BUFFER_SIZE   64
 
 /* Global USB buffers */
 static uint8_t usb_in_buffer[JLINK_IN_BUFFER_SIZE];
 static uint8_t usb_out_buffer[JLINK_OUT_BUFFER_SIZE];
-static uint8_t usb_emu_result_buffer[JLINK_EMU_RESULT_BUFFER_SIZE];
 
 /* Constants for JLink command */
 #define EMU_CMD_VERSION                        0x01
@@ -231,7 +229,6 @@ static int jlink_usb_message(struct jlink *jlink, int out_length, int in_length)
 static int jlink_usb_io(struct jlink *jlink, int out_length, int in_length);
 static int jlink_usb_write(struct jlink *jlink, int out_length);
 static int jlink_usb_read(struct jlink *jlink, int expected_size);
-static int jlink_usb_read_emu_result(struct jlink *jlink);
 
 /* helper functions */
 static int jlink_get_version_info(void);
@@ -1421,10 +1418,17 @@ static int jlink_tap_execute(void)
        jlink_last_state = jtag_debug_state_machine(tms_buffer, tdi_buffer,
                        tap_length, jlink_last_state);
 
-       result = jlink_usb_message(jlink_handle, 4 + 2 * byte_length, byte_length);
-       if (result != byte_length) {
-               LOG_ERROR("jlink_tap_execute, wrong result %d (expected %d)",
-                               result, byte_length);
+       result = jlink_usb_message(jlink_handle, 4 + 2 * byte_length,
+                       use_jtag3 ? byte_length + 1 : byte_length);
+       if (result != ERROR_OK) {
+               LOG_ERROR("jlink_tap_execute failed USB io (%d)", result);
+               jlink_tap_init();
+               return ERROR_JTAG_QUEUE_FAILED;
+       }
+
+       result = use_jtag3 ? usb_in_buffer[byte_length] : 0;
+       if (result != 0) {
+               LOG_ERROR("jlink_tap_execute failed, result %d", result);
                jlink_tap_init();
                return ERROR_JTAG_QUEUE_FAILED;
        }
@@ -1539,44 +1543,12 @@ static int jlink_usb_message(struct jlink *jlink, int out_length, int in_length)
        }
 
        result = jlink_usb_read(jlink, in_length);
-       if ((result != in_length) && (result != (in_length + 1))) {
+       if (result != in_length) {
                LOG_ERROR("usb_bulk_read failed (requested=%d, result=%d)",
                                in_length, result);
                return ERROR_JTAG_DEVICE_ERROR;
        }
-
-       if (jlink_hw_jtag_version < 3)
-               return result;
-
-       int result2 = ERROR_OK;
-       if (result == in_length) {
-               /* Must read the result from the EMU too */
-               result2 = jlink_usb_read_emu_result(jlink);
-               if (1 != result2) {
-                       LOG_ERROR("jlink_usb_read_emu_result retried requested = 1, "
-                                       "result=%d, in_length=%i", result2, in_length);
-                       /* Try again once, should only happen if (in_length%64 == 0) */
-                       result2 = jlink_usb_read_emu_result(jlink);
-                       if (1 != result2) {
-                               LOG_ERROR("jlink_usb_read_emu_result failed "
-                                       "(requested = 1, result=%d)", result2);
-                               return ERROR_JTAG_DEVICE_ERROR;
-                       }
-               }
-
-               /* Check the result itself */
-               result2 = usb_emu_result_buffer[0];
-       } else {
-               /* Save the result, then remove it from return value */
-               result2 = usb_in_buffer[result--];
-       }
-
-       if (result2) {
-               LOG_ERROR("jlink_usb_message failed with result=%d)", result2);
-               return ERROR_JTAG_DEVICE_ERROR;
-       }
-
-       return result;
+       return ERROR_OK;
 }
 
 /* calls the given usb_bulk_* function, allowing for the data to
@@ -1652,19 +1624,6 @@ static int jlink_usb_read(struct jlink *jlink, int expected_size)
        return result;
 }
 
-/* Read the result from the previous EMU cmd into result_buffer. */
-static int jlink_usb_read_emu_result(struct jlink *jlink)
-{
-       int result = usb_bulk_read_ex(jlink->usb_handle, jlink_read_ep,
-               (char *)usb_emu_result_buffer, 1 /* JLINK_EMU_RESULT_BUFFER_SIZE */,
-               JLINK_USB_TIMEOUT);
-
-       DEBUG_JTAG_IO("jlink_usb_read_result, result = %d", result);
-
-       jlink_debug_buffer(usb_emu_result_buffer, result);
-       return result;
-}
-
 /*
  * Send a message and receive the reply - simple messages.
  *