]> git.sur5r.net Git - openocd/blobdiff - src/flash/nor/at91samd.c
flash/nor: at91samd modified to use real erase sector size
[openocd] / src / flash / nor / at91samd.c
index 9eec0d0ead86b0a0aba89e831067f2a4f508485f..ad88c5143dbe8e544187224cf475dc0c5790a133 100644 (file)
@@ -13,9 +13,7 @@
  *   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.,                                       *
- *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.           *
+ *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  ***************************************************************************/
 
 #ifdef HAVE_CONFIG_H
 #endif
 
 #include "imp.h"
+#include "helper/binarybuffer.h"
 
-#define SAMD_NUM_SECTORS       16
+#include <target/cortex_m.h>
+
+#define SAMD_NUM_PROT_BLOCKS   16
+#define SAMD_PAGE_SIZE_MAX     1024
 
 #define SAMD_FLASH                     ((uint32_t)0x00000000)  /* physical Flash memory */
+#define SAMD_USER_ROW          ((uint32_t)0x00804000)  /* User Row of Flash */
 #define SAMD_PAC1                      0x41000000      /* Peripheral Access Control 1 */
 #define SAMD_DSU                       0x41002000      /* Device Service Unit */
 #define SAMD_NVMCTRL           0x41004000      /* Non-volatile memory controller */
 
+#define SAMD_DSU_STATUSA        1               /* DSU status register */
 #define SAMD_DSU_DID           0x18            /* Device ID register */
+#define SAMD_DSU_CTRL_EXT      0x100           /* CTRL register, external access */
 
 #define SAMD_NVMCTRL_CTRLA             0x00    /* NVM control A register */
 #define SAMD_NVMCTRL_CTRLB             0x04    /* NVM control B register */
 #define SAMD_NVM_CMD_SSB       0x45            /* Set Security Bit */
 #define SAMD_NVM_CMD_INVALL    0x46            /* Invalidate all caches */
 
+/* NVMCTRL bits */
+#define SAMD_NVM_CTRLB_MANW 0x80
+
 /* Known identifiers */
 #define SAMD_PROCESSOR_M0      0x01
 #define SAMD_FAMILY_D          0x00
+#define SAMD_FAMILY_L          0x01
+#define SAMD_FAMILY_C          0x02
 #define SAMD_SERIES_20         0x00
 #define SAMD_SERIES_21         0x01
+#define SAMD_SERIES_22         0x02
 #define SAMD_SERIES_10         0x02
 #define SAMD_SERIES_11         0x03
+#define SAMD_SERIES_09         0x04
+
+/* Device ID macros */
+#define SAMD_GET_PROCESSOR(id) (id >> 28)
+#define SAMD_GET_FAMILY(id) (((id >> 23) & 0x1F))
+#define SAMD_GET_SERIES(id) (((id >> 16) & 0x3F))
+#define SAMD_GET_DEVSEL(id) (id & 0xFF)
 
 struct samd_part {
        uint8_t id;
@@ -72,6 +90,13 @@ struct samd_part {
        uint32_t ram_kb;
 };
 
+/* Known SAMD09 parts. DID reset values missing in RM, see
+ * https://github.com/avrxml/asf/blob/master/sam0/utils/cmsis/samd09/include/ */
+static const struct samd_part samd09_parts[] = {
+       { 0x0, "SAMD09D14A", 16, 4 },
+       { 0x7, "SAMD09C13A", 8, 4 },
+};
+
 /* Known SAMD10 parts */
 static const struct samd_part samd10_parts[] = {
        { 0x0, "SAMD10D14AMU", 16, 4 },
@@ -134,6 +159,13 @@ static const struct samd_part samd21_parts[] = {
        { 0xC, "SAMD21E16A", 64, 8 },
        { 0xD, "SAMD21E15A", 32, 4 },
        { 0xE, "SAMD21E14A", 16, 2 },
+    /* Below are B Variants (Table 3-7 from rev I of datasheet) */
+       { 0x20, "SAMD21J16B", 64, 8 },
+       { 0x21, "SAMD21J15B", 32, 4 },
+       { 0x23, "SAMD21G16B", 64, 8 },
+       { 0x24, "SAMD21G15B", 32, 4 },
+       { 0x26, "SAMD21E16B", 64, 8 },
+       { 0x27, "SAMD21E15B", 32, 4 },
 };
 
 /* Known SAMR21 parts. */
@@ -146,6 +178,74 @@ static const struct samd_part samr21_parts[] = {
        { 0x1E, "SAMR21E16A",  64, 32 },
 };
 
+/* Known SAML21 parts. */
+static const struct samd_part saml21_parts[] = {
+       { 0x00, "SAML21J18A", 256, 32 },
+       { 0x01, "SAML21J17A", 128, 16 },
+       { 0x02, "SAML21J16A", 64, 8 },
+       { 0x05, "SAML21G18A", 256, 32 },
+       { 0x06, "SAML21G17A", 128, 16 },
+       { 0x07, "SAML21G16A", 64, 8 },
+       { 0x0A, "SAML21E18A", 256, 32 },
+       { 0x0B, "SAML21E17A", 128, 16 },
+       { 0x0C, "SAML21E16A", 64, 8 },
+       { 0x0D, "SAML21E15A", 32, 4 },
+       { 0x0F, "SAML21J18B", 256, 32 },
+       { 0x10, "SAML21J17B", 128, 16 },
+       { 0x11, "SAML21J16B", 64, 8 },
+       { 0x14, "SAML21G18B", 256, 32 },
+       { 0x15, "SAML21G17B", 128, 16 },
+       { 0x16, "SAML21G16B", 64, 8 },
+       { 0x19, "SAML21E18B", 256, 32 },
+       { 0x1A, "SAML21E17B", 128, 16 },
+       { 0x1B, "SAML21E16B", 64, 8 },
+       { 0x1C, "SAML21E15B", 32, 4 },
+};
+
+/* Known SAML22 parts. */
+static const struct samd_part saml22_parts[] = {
+       { 0x00, "SAML22N18A", 256, 32 },
+       { 0x01, "SAML22N17A", 128, 16 },
+       { 0x02, "SAML22N16A", 64, 8 },
+       { 0x05, "SAML22J18A", 256, 32 },
+       { 0x06, "SAML22J17A", 128, 16 },
+       { 0x07, "SAML22J16A", 64, 8 },
+       { 0x0A, "SAML22G18A", 256, 32 },
+       { 0x0B, "SAML22G17A", 128, 16 },
+       { 0x0C, "SAML22G16A", 64, 8 },
+};
+
+/* Known SAMC20 parts. */
+static const struct samd_part samc20_parts[] = {
+       { 0x00, "SAMC20J18A", 256, 32 },
+       { 0x01, "SAMC20J17A", 128, 16 },
+       { 0x02, "SAMC20J16A", 64, 8 },
+       { 0x03, "SAMC20J15A", 32, 4 },
+       { 0x05, "SAMC20G18A", 256, 32 },
+       { 0x06, "SAMC20G17A", 128, 16 },
+       { 0x07, "SAMC20G16A", 64, 8 },
+       { 0x08, "SAMC20G15A", 32, 4 },
+       { 0x0A, "SAMC20E18A", 256, 32 },
+       { 0x0B, "SAMC20E17A", 128, 16 },
+       { 0x0C, "SAMC20E16A", 64, 8 },
+       { 0x0D, "SAMC20E15A", 32, 4 },
+};
+
+/* Known SAMC21 parts. */
+static const struct samd_part samc21_parts[] = {
+       { 0x00, "SAMC21J18A", 256, 32 },
+       { 0x01, "SAMC21J17A", 128, 16 },
+       { 0x02, "SAMC21J16A", 64, 8 },
+       { 0x03, "SAMC21J15A", 32, 4 },
+       { 0x05, "SAMC21G18A", 256, 32 },
+       { 0x06, "SAMC21G17A", 128, 16 },
+       { 0x07, "SAMC21G16A", 64, 8 },
+       { 0x08, "SAMC21G15A", 32, 4 },
+       { 0x0A, "SAMC21E18A", 256, 32 },
+       { 0x0B, "SAMC21E17A", 128, 16 },
+       { 0x0C, "SAMC21E16A", 64, 8 },
+       { 0x0D, "SAMC21E15A", 32, 4 },
+};
 
 /* Each family of parts contains a parts table in the DEVSEL field of DID.  The
  * processor ID, family ID, and series ID are used to determine which exact
@@ -166,16 +266,27 @@ static const struct samd_family samd_families[] = {
                samd21_parts, ARRAY_SIZE(samd21_parts) },
        { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_21,
                samr21_parts, ARRAY_SIZE(samr21_parts) },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_09,
+               samd09_parts, ARRAY_SIZE(samd09_parts) },
        { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_10,
                samd10_parts, ARRAY_SIZE(samd10_parts) },
        { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_11,
                samd11_parts, ARRAY_SIZE(samd11_parts) },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_L, SAMD_SERIES_21,
+               saml21_parts, ARRAY_SIZE(saml21_parts) },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_L, SAMD_SERIES_22,
+               saml22_parts, ARRAY_SIZE(saml22_parts) },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_C, SAMD_SERIES_20,
+               samc20_parts, ARRAY_SIZE(samc20_parts) },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_C, SAMD_SERIES_21,
+               samc21_parts, ARRAY_SIZE(samc21_parts) },
 };
 
 struct samd_info {
        uint32_t page_size;
        int num_pages;
        int sector_size;
+       int prot_block_size;
 
        bool probed;
        struct target *target;
@@ -184,12 +295,14 @@ struct samd_info {
 
 static struct samd_info *samd_chips;
 
+
+
 static const struct samd_part *samd_find_part(uint32_t id)
 {
-       uint8_t processor = (id >> 28);
-       uint8_t family = (id >> 24) & 0x0F;
-       uint8_t series = (id >> 16) & 0xFF;
-       uint8_t devsel = id & 0xFF;
+       uint8_t processor = SAMD_GET_PROCESSOR(id);
+       uint8_t family = SAMD_GET_FAMILY(id);
+       uint8_t series = SAMD_GET_SERIES(id);
+       uint8_t devsel = SAMD_GET_DEVSEL(id);
 
        for (unsigned i = 0; i < ARRAY_SIZE(samd_families); i++) {
                if (samd_families[i].processor == processor &&
@@ -207,7 +320,7 @@ static const struct samd_part *samd_find_part(uint32_t id)
 
 static int samd_protect_check(struct flash_bank *bank)
 {
-       int res;
+       int res, prot_block;
        uint16_t lock;
 
        res = target_read_u16(bank->target,
@@ -216,15 +329,37 @@ static int samd_protect_check(struct flash_bank *bank)
                return res;
 
        /* Lock bits are active-low */
-       for (int i = 0; i < bank->num_sectors; i++)
-               bank->sectors[i].is_protected = !(lock & (1<<i));
+       for (prot_block = 0; prot_block < bank->num_prot_blocks; prot_block++)
+               bank->prot_blocks[prot_block].is_protected = !(lock & (1u<<prot_block));
 
        return ERROR_OK;
 }
 
+static int samd_get_flash_page_info(struct target *target,
+               uint32_t *sizep, int *nump)
+{
+       int res;
+       uint32_t param;
+
+       res = target_read_u32(target, SAMD_NVMCTRL + SAMD_NVMCTRL_PARAM, &param);
+       if (res == ERROR_OK) {
+               /* The PSZ field (bits 18:16) indicate the page size bytes as 2^(3+n)
+                * so 0 is 8KB and 7 is 1024KB. */
+               if (sizep)
+                       *sizep = (8 << ((param >> 16) & 0x7));
+               /* The NVMP field (bits 15:0) indicates the total number of pages */
+               if (nump)
+                       *nump = param & 0xFFFF;
+       } else {
+               LOG_ERROR("Couldn't read NVM Parameters register");
+       }
+
+       return res;
+}
+
 static int samd_probe(struct flash_bank *bank)
 {
-       uint32_t id, param;
+       uint32_t id;
        int res;
        struct samd_info *chip = (struct samd_info *)bank->driver_priv;
        const struct samd_part *part;
@@ -240,27 +375,19 @@ static int samd_probe(struct flash_bank *bank)
 
        part = samd_find_part(id);
        if (part == NULL) {
-               LOG_ERROR("Couldn't find part correspoding to DID %08" PRIx32, id);
+               LOG_ERROR("Couldn't find part corresponding to DID %08" PRIx32, id);
                return ERROR_FAIL;
        }
 
-       res = target_read_u32(bank->target,
-                       SAMD_NVMCTRL + SAMD_NVMCTRL_PARAM, &param);
+       bank->size = part->flash_kb * 1024;
+
+       res = samd_get_flash_page_info(bank->target, &chip->page_size,
+                       &chip->num_pages);
        if (res != ERROR_OK) {
-               LOG_ERROR("Couldn't read NVM Parameters register");
+               LOG_ERROR("Couldn't determine Flash page size");
                return res;
        }
 
-       bank->size = part->flash_kb * 1024;
-
-       chip->sector_size = bank->size / SAMD_NUM_SECTORS;
-
-       /* The PSZ field (bits 18:16) indicate the page size bytes as 2^(3+n) so
-        * 0 is 8KB and 7 is 1024KB. */
-       chip->page_size = (8 << ((param >> 16) & 0x7));
-       /* The NVMP field (bits 15:0) indicates the total number of pages */
-       chip->num_pages = param & 0xFFFF;
-
        /* Sanity check: the total flash size in the DSU should match the page size
         * multiplied by the number of pages. */
        if (bank->size != chip->num_pages * chip->page_size) {
@@ -269,21 +396,23 @@ static int samd_probe(struct flash_bank *bank)
                                part->flash_kb, chip->num_pages, chip->page_size);
        }
 
+       /* Erase granularity = 1 row = 4 pages */
+       chip->sector_size = chip->page_size * 4;
+
        /* Allocate the sector table */
-       bank->num_sectors = SAMD_NUM_SECTORS;
-       bank->sectors = calloc(bank->num_sectors, sizeof((bank->sectors)[0]));
+       bank->num_sectors = chip->num_pages / 4;
+       bank->sectors = alloc_block_array(0, chip->sector_size, bank->num_sectors);
        if (!bank->sectors)
                return ERROR_FAIL;
 
-       /* Fill out the sector information: all SAMD sectors are the same size and
-        * there is always a fixed number of them. */
-       for (int i = 0; i < bank->num_sectors; i++) {
-               bank->sectors[i].size = chip->sector_size;
-               bank->sectors[i].offset = i * chip->sector_size;
-               /* mark as unknown */
-               bank->sectors[i].is_erased = -1;
-               bank->sectors[i].is_protected = -1;
-       }
+       /* 16 protection blocks per device */
+       chip->prot_block_size = bank->size / SAMD_NUM_PROT_BLOCKS;
+
+       /* Allocate the table of protection blocks */
+       bank->num_prot_blocks = SAMD_NUM_PROT_BLOCKS;
+       bank->prot_blocks = alloc_block_array(0, chip->prot_block_size, bank->num_prot_blocks);
+       if (!bank->prot_blocks)
+               return ERROR_FAIL;
 
        samd_protect_check(bank);
 
@@ -296,121 +425,76 @@ static int samd_probe(struct flash_bank *bank)
        return ERROR_OK;
 }
 
-static bool samd_check_error(struct target *target)
+static int samd_check_error(struct target *target)
 {
-       int ret;
-       bool error;
+       int ret, ret2;
        uint16_t status;
 
        ret = target_read_u16(target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_STATUS, &status);
        if (ret != ERROR_OK) {
                LOG_ERROR("Can't read NVM status");
-               return true;
+               return ret;
        }
 
-       if (status & 0x001C) {
-               if (status & (1 << 4)) /* NVME */
-                       LOG_ERROR("SAMD: NVM Error");
-               if (status & (1 << 3)) /* LOCKE */
-                       LOG_ERROR("SAMD: NVM lock error");
-               if (status & (1 << 2)) /* PROGE */
-                       LOG_ERROR("SAMD: NVM programming error");
+       if ((status & 0x001C) == 0)
+               return ERROR_OK;
 
-               error = true;
-       } else {
-               error = false;
+       if (status & (1 << 4)) { /* NVME */
+               LOG_ERROR("SAMD: NVM Error");
+               ret = ERROR_FLASH_OPERATION_FAILED;
+       }
+
+       if (status & (1 << 3)) { /* LOCKE */
+               LOG_ERROR("SAMD: NVM lock error");
+               ret = ERROR_FLASH_PROTECTED;
+       }
+
+       if (status & (1 << 2)) { /* PROGE */
+               LOG_ERROR("SAMD: NVM programming error");
+               ret = ERROR_FLASH_OPER_UNSUPPORTED;
        }
 
        /* Clear the error conditions by writing a one to them */
-       ret = target_write_u16(target,
+       ret2 = target_write_u16(target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_STATUS, status);
-       if (ret != ERROR_OK)
+       if (ret2 != ERROR_OK)
                LOG_ERROR("Can't clear NVM error conditions");
 
-       return error;
+       return ret;
 }
 
 static int samd_issue_nvmctrl_command(struct target *target, uint16_t cmd)
 {
+       int res;
+
        if (target->state != TARGET_HALTED) {
                LOG_ERROR("Target not halted");
                return ERROR_TARGET_NOT_HALTED;
        }
 
-       /* Read current configuration. */
-       uint16_t tmp = 0;
-       int res = target_read_u16(target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB,
-                       &tmp);
-       if (res != ERROR_OK)
-               return res;
-
-       /* Set cache disable. */
-       res = target_write_u16(target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB,
-                       tmp | (1<<18));
-       if (res != ERROR_OK)
-               return res;
-
        /* Issue the NVM command */
-       int res_cmd = target_write_u16(target,
+       res = target_write_u16(target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLA, SAMD_NVM_CMD(cmd));
-
-       /* Try to restore configuration, regardless of NVM command write
-        * status. */
-       res = target_write_u16(target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB, tmp);
-
-       if (res_cmd != ERROR_OK)
-               return res_cmd;
-
        if (res != ERROR_OK)
                return res;
 
        /* Check to see if the NVM command resulted in an error condition. */
-       if (samd_check_error(target))
-               return ERROR_FAIL;
-
-       return ERROR_OK;
-}
-
-static int samd_protect(struct flash_bank *bank, int set, int first, int last)
-{
-       int res;
-       struct samd_info *chip = (struct samd_info *)bank->driver_priv;
-
-       res = ERROR_OK;
-
-       for (int s = first; s <= last; s++) {
-               if (set != bank->sectors[s].is_protected) {
-                       /* Load an address that is within this sector (we use offset 0) */
-                       res = target_write_u32(bank->target, SAMD_NVMCTRL + SAMD_NVMCTRL_ADDR,
-                                              s * chip->sector_size);
-                       if (res != ERROR_OK)
-                               goto exit;
-
-                       /* Tell the controller to lock that sector */
-                       res = samd_issue_nvmctrl_command(bank->target,
-                                       set ? SAMD_NVM_CMD_LR : SAMD_NVM_CMD_UR);
-                       if (res != ERROR_OK)
-                               goto exit;
-               }
-       }
-exit:
-       samd_protect_check(bank);
-
-       return res;
+       return samd_check_error(target);
 }
 
-static int samd_erase_row(struct flash_bank *bank, uint32_t address)
+static int samd_erase_row(struct target *target, uint32_t address)
 {
        int res;
 
        /* Set an address contained in the row to be erased */
-       res = target_write_u32(bank->target,
+       res = target_write_u32(target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_ADDR, address >> 1);
 
-       /* Issue the Erase Row command to erase that row */
+       /* Issue the Erase Row command to erase that row. */
        if (res == ERROR_OK)
-               res = samd_issue_nvmctrl_command(bank->target, SAMD_NVM_CMD_ER);
+               res = samd_issue_nvmctrl_command(target,
+                               address == SAMD_USER_ROW ? SAMD_NVM_CMD_EAR : SAMD_NVM_CMD_ER);
 
        if (res != ERROR_OK)  {
                LOG_ERROR("Failed to erase row containing %08" PRIx32, address);
@@ -420,162 +504,202 @@ static int samd_erase_row(struct flash_bank *bank, uint32_t address)
        return ERROR_OK;
 }
 
-static int samd_erase(struct flash_bank *bank, int first, int last)
+static bool is_user_row_reserved_bit(uint8_t bit)
 {
-       int res;
-       int rows_in_sector;
-       struct samd_info *chip = (struct samd_info *)bank->driver_priv;
+       /* See Table 9-3 in the SAMD20 datasheet for more information. */
+       switch (bit) {
+               /* Reserved bits */
+               case 3:
+               case 7:
+               /* Voltage regulator internal configuration with default value of 0x70,
+                * may not be changed. */
+               case 17 ... 24:
+               /* 41 is voltage regulator internal configuration and must not be
+                * changed.  42 through 47 are reserved. */
+               case 41 ... 47:
+                       return true;
+               default:
+                       break;
+       }
 
-       if (bank->target->state != TARGET_HALTED) {
-               LOG_ERROR("Target not halted");
+       return false;
+}
 
-               return ERROR_TARGET_NOT_HALTED;
+/* Modify the contents of the User Row in Flash.  These are described in Table
+ * 9-3 of the SAMD20 datasheet.  The User Row itself has a size of one page
+ * and contains a combination of "fuses" and calibration data in bits 24:17.
+ * We therefore try not to erase the row's contents unless we absolutely have
+ * to and we don't permit modifying reserved bits. */
+static int samd_modify_user_row(struct target *target, uint32_t value,
+               uint8_t startb, uint8_t endb)
+{
+       int res;
+       uint32_t nvm_ctrlb;
+       bool manual_wp = true;
+
+       if (is_user_row_reserved_bit(startb) || is_user_row_reserved_bit(endb)) {
+               LOG_ERROR("Can't modify bits in the requested range");
+               return ERROR_FAIL;
        }
 
-       if (!chip->probed) {
-               if (samd_probe(bank) != ERROR_OK)
-                       return ERROR_FLASH_BANK_NOT_PROBED;
+       /* Check if we need to do manual page write commands */
+       res = target_read_u32(target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB, &nvm_ctrlb);
+       if (res == ERROR_OK)
+               manual_wp = (nvm_ctrlb & SAMD_NVM_CTRLB_MANW) != 0;
+
+       /* Retrieve the MCU's page size, in bytes. This is also the size of the
+        * entire User Row. */
+       uint32_t page_size;
+       res = samd_get_flash_page_info(target, &page_size, NULL);
+       if (res != ERROR_OK) {
+               LOG_ERROR("Couldn't determine Flash page size");
+               return res;
        }
 
-       /* The SAMD NVM has row erase granularity.  There are four pages in a row
-        * and the number of rows in a sector depends on the sector size, which in
-        * turn depends on the Flash capacity as there is a fixed number of
-        * sectors. */
-       rows_in_sector = chip->sector_size / (chip->page_size * 4);
+       /* Make sure the size is sane before we allocate. */
+       assert(page_size > 0 && page_size <= SAMD_PAGE_SIZE_MAX);
 
-       /* For each sector to be erased */
-       for (int s = first; s <= last; s++) {
-               if (bank->sectors[s].is_protected) {
-                       LOG_ERROR("SAMD: failed to erase sector %d. That sector is write-protected", s);
-                       return ERROR_FLASH_OPERATION_FAILED;
-               }
+       /* Make sure we're within the single page that comprises the User Row. */
+       if (startb >= (page_size * 8) || endb >= (page_size * 8)) {
+               LOG_ERROR("Can't modify bits outside the User Row page range");
+               return ERROR_FAIL;
+       }
 
-               if (!bank->sectors[s].is_erased) {
-                       /* For each row in that sector */
-                       for (int r = s * rows_in_sector; r < (s + 1) * rows_in_sector; r++) {
-                               res = samd_erase_row(bank, r * chip->page_size * 4);
-                               if (res != ERROR_OK) {
-                                       LOG_ERROR("SAMD: failed to erase sector %d", s);
-                                       return res;
-                               }
-                       }
+       uint8_t *buf = malloc(page_size);
+       if (!buf)
+               return ERROR_FAIL;
 
-                       bank->sectors[s].is_erased = 1;
+       /* Read the user row (comprising one page) by words. */
+       res = target_read_memory(target, SAMD_USER_ROW, 4, page_size / 4, buf);
+       if (res != ERROR_OK)
+               goto out_user_row;
+
+       /* We will need to erase before writing if the new value needs a '1' in any
+        * position for which the current value had a '0'.  Otherwise we can avoid
+        * erasing. */
+       uint32_t cur = buf_get_u32(buf, startb, endb - startb + 1);
+       if ((~cur) & value) {
+               res = samd_erase_row(target, SAMD_USER_ROW);
+               if (res != ERROR_OK) {
+                       LOG_ERROR("Couldn't erase user row");
+                       goto out_user_row;
                }
        }
 
-       return ERROR_OK;
-}
+       /* Modify */
+       buf_set_u32(buf, startb, endb - startb + 1, value);
 
-static struct flash_sector *samd_find_sector_by_address(struct flash_bank *bank, uint32_t address)
-{
-       struct samd_info *chip = (struct samd_info *)bank->driver_priv;
+       /* Write the page buffer back out to the target. */
+       res = target_write_memory(target, SAMD_USER_ROW, 4, page_size / 4, buf);
+       if (res != ERROR_OK)
+               goto out_user_row;
 
-       for (int i = 0; i < bank->num_sectors; i++) {
-               if (bank->sectors[i].offset <= address &&
-                   address < bank->sectors[i].offset + chip->sector_size)
-                       return &bank->sectors[i];
+       if (manual_wp) {
+               /* Trigger flash write */
+               res = samd_issue_nvmctrl_command(target, SAMD_NVM_CMD_WAP);
+       } else {
+               res = samd_check_error(target);
        }
-       return NULL;
-}
 
-/* Write an entire row (four pages) from host buffer 'buf' to row-aligned
- * 'address' in the Flash. */
-static int samd_write_row(struct flash_bank *bank, uint32_t address,
-               const uint8_t *buf)
-{
-       int res;
-       struct samd_info *chip = (struct samd_info *)bank->driver_priv;
+out_user_row:
+       free(buf);
 
-       struct flash_sector *sector = samd_find_sector_by_address(bank, address);
+       return res;
+}
 
-       if (!sector) {
-               LOG_ERROR("Can't find sector corresponding to address 0x%08" PRIx32, address);
-               return ERROR_FLASH_OPERATION_FAILED;
-       }
+static int samd_protect(struct flash_bank *bank, int set, int first_prot_bl, int last_prot_bl)
+{
+       int res = ERROR_OK;
+       int prot_block;
 
-       if (sector->is_protected) {
-               LOG_ERROR("Trying to write to a protected sector at 0x%08" PRIx32, address);
-               return ERROR_FLASH_OPERATION_FAILED;
+       /* We can issue lock/unlock region commands with the target running but
+        * the settings won't persist unless we're able to modify the LOCK regions
+        * and that requires the target to be halted. */
+       if (bank->target->state != TARGET_HALTED) {
+               LOG_ERROR("Target not halted");
+               return ERROR_TARGET_NOT_HALTED;
        }
 
-       /* Erase the row that we'll be writing to */
-       res = samd_erase_row(bank, address);
-       if (res != ERROR_OK)
-               return res;
-
-       /* Now write the pages in this row. */
-       for (unsigned int i = 0; i < 4; i++) {
-               bool error;
+       for (prot_block = first_prot_bl; prot_block <= last_prot_bl; prot_block++) {
+               if (set != bank->prot_blocks[prot_block].is_protected) {
+                       /* Load an address that is within this protection block (we use offset 0) */
+                       res = target_write_u32(bank->target,
+                                                       SAMD_NVMCTRL + SAMD_NVMCTRL_ADDR,
+                                                       bank->prot_blocks[prot_block].offset >> 1);
+                       if (res != ERROR_OK)
+                               goto exit;
 
-               /* Write the page contents to the target's page buffer.  A page write
-                * is issued automatically once the last location is written in the
-                * page buffer (ie: a complete page has been written out). */
-               res = target_write_memory(bank->target, address, 4,
-                               chip->page_size / 4, buf);
-               if (res != ERROR_OK) {
-                       LOG_ERROR("%s: %d", __func__, __LINE__);
-                       return res;
+                       /* Tell the controller to lock that block */
+                       res = samd_issue_nvmctrl_command(bank->target,
+                                       set ? SAMD_NVM_CMD_LR : SAMD_NVM_CMD_UR);
+                       if (res != ERROR_OK)
+                               goto exit;
                }
+       }
 
-               error = samd_check_error(bank->target);
-               if (error)
-                       return ERROR_FAIL;
+       /* We've now applied our changes, however they will be undone by the next
+        * reset unless we also apply them to the LOCK bits in the User Page.  The
+        * LOCK bits start at bit 48, corresponding to Sector 0 and end with bit 63,
+        * corresponding to Sector 15.  A '1' means unlocked and a '0' means
+        * locked.  See Table 9-3 in the SAMD20 datasheet for more details. */
 
-               /* Next page */
-               address += chip->page_size;
-               buf += chip->page_size;
-       }
+       res = samd_modify_user_row(bank->target, set ? 0x0000 : 0xFFFF,
+                       48 + first_prot_bl, 48 + last_prot_bl);
+       if (res != ERROR_OK)
+               LOG_WARNING("SAMD: protect settings were not made persistent!");
 
-       sector->is_erased = 0;
+       res = ERROR_OK;
+
+exit:
+       samd_protect_check(bank);
 
        return res;
 }
 
-/* Write partial contents into row-aligned 'address' on the Flash from host
- * buffer 'buf' by writing 'nb' of 'buf' at 'row_offset' into the Flash row. */
-static int samd_write_row_partial(struct flash_bank *bank, uint32_t address,
-               const uint8_t *buf, uint32_t row_offset, uint32_t nb)
+static int samd_erase(struct flash_bank *bank, int first_sect, int last_sect)
 {
-       int res;
+       int res, s;
        struct samd_info *chip = (struct samd_info *)bank->driver_priv;
-       uint32_t row_size = chip->page_size * 4;
-       uint8_t *rb = malloc(row_size);
-       if (!rb)
-               return ERROR_FAIL;
 
-       assert(row_offset + nb < row_size);
-       assert((address % row_size) == 0);
+       if (bank->target->state != TARGET_HALTED) {
+               LOG_ERROR("Target not halted");
 
-       /* Retrieve the full row contents from Flash */
-       res = target_read_memory(bank->target, address, 4, row_size / 4, rb);
-       if (res != ERROR_OK) {
-               free(rb);
-               return res;
+               return ERROR_TARGET_NOT_HALTED;
        }
 
-       /* Insert our partial row over the data from Flash */
-       memcpy(rb + (row_offset % row_size), buf, nb);
+       if (!chip->probed) {
+               if (samd_probe(bank) != ERROR_OK)
+                       return ERROR_FLASH_BANK_NOT_PROBED;
+       }
 
-       /* Write the row back out */
-       res = samd_write_row(bank, address, rb);
-       free(rb);
+       /* For each sector to be erased */
+       for (s = first_sect; s <= last_sect; s++) {
+               res = samd_erase_row(bank->target, bank->sectors[s].offset);
+               if (res != ERROR_OK) {
+                       LOG_ERROR("SAMD: failed to erase sector %d at 0x%08" PRIx32, s, bank->sectors[s].offset);
+                       return res;
+               }
+       }
 
-       return res;
+       return ERROR_OK;
 }
 
+
 static int samd_write(struct flash_bank *bank, const uint8_t *buffer,
                uint32_t offset, uint32_t count)
 {
        int res;
+       uint32_t nvm_ctrlb;
        uint32_t address;
-       uint32_t nb = 0;
+       uint32_t pg_offset;
+       uint32_t nb;
+       uint32_t nw;
        struct samd_info *chip = (struct samd_info *)bank->driver_priv;
-       uint32_t row_size = chip->page_size * 4;
+       uint8_t *pb = NULL;
+       bool manual_wp;
 
        if (bank->target->state != TARGET_HALTED) {
                LOG_ERROR("Target not halted");
-
                return ERROR_TARGET_NOT_HALTED;
        }
 
@@ -584,61 +708,97 @@ static int samd_write(struct flash_bank *bank, const uint8_t *buffer,
                        return ERROR_FLASH_BANK_NOT_PROBED;
        }
 
-       if (offset % row_size) {
-               /* We're starting at an unaligned offset so we'll write a partial row
-                * comprising that offset and up to the end of that row. */
-               nb = row_size - (offset % row_size);
-               if (nb > count)
-                       nb = count;
-       } else if (count < row_size) {
-               /* We're writing an aligned but partial row. */
-               nb = count;
+       /* Check if we need to do manual page write commands */
+       res = target_read_u32(bank->target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB, &nvm_ctrlb);
+
+       if (res != ERROR_OK)
+               return res;
+
+       if (nvm_ctrlb & SAMD_NVM_CTRLB_MANW)
+               manual_wp = true;
+       else
+               manual_wp = false;
+
+       res = samd_issue_nvmctrl_command(bank->target, SAMD_NVM_CMD_PBC);
+       if (res != ERROR_OK) {
+               LOG_ERROR("%s: %d", __func__, __LINE__);
+               return res;
        }
 
-       address = (offset / row_size) * row_size + bank->base;
+       while (count) {
+               nb = chip->page_size - offset % chip->page_size;
+               if (count < nb)
+                       nb = count;
 
-       if (nb > 0) {
-               res = samd_write_row_partial(bank, address, buffer,
-                               offset % row_size, nb);
-               if (res != ERROR_OK)
-                       return res;
+               address = bank->base + offset;
+               pg_offset = offset % chip->page_size;
 
-               /* We're done with the row contents */
-               count -= nb;
-               offset += nb;
-               buffer += row_size;
-       }
-
-       /* There's at least one aligned row to write out. */
-       if (count >= row_size) {
-               int nr = count / row_size + ((count % row_size) ? 1 : 0);
-               unsigned int r = 0;
-
-               for (unsigned int i = address / row_size;
-                               (i < (address / row_size) + nr) && count > 0; i++) {
-                       address = (i * row_size) + bank->base;
-
-                       if (count >= row_size) {
-                               res = samd_write_row(bank, address, buffer + (r * row_size));
-                               /* Advance one row */
-                               offset += row_size;
-                               count -= row_size;
-                       } else {
-                               res = samd_write_row_partial(bank, address,
-                                               buffer + (r * row_size), 0, count);
-                               /* We're done after this. */
-                               offset += count;
-                               count = 0;
+               if (offset % 4 || (offset + nb) % 4) {
+                       /* Either start or end of write is not word aligned */
+                       if (!pb) {
+                               pb = malloc(chip->page_size);
+                               if (!pb)
+                                       return ERROR_FAIL;
                        }
 
-                       r++;
+                       /* Set temporary page buffer to 0xff and overwrite the relevant part */
+                       memset(pb, 0xff, chip->page_size);
+                       memcpy(pb + pg_offset, buffer, nb);
+
+                       /* Align start address to a word boundary */
+                       address -= offset % 4;
+                       pg_offset -= offset % 4;
+                       assert(pg_offset % 4 == 0);
+
+                       /* Extend length to whole words */
+                       nw = (nb + offset % 4 + 3) / 4;
+                       assert(pg_offset + 4 * nw <= chip->page_size);
+
+                       /* Now we have original data extended by 0xff bytes
+                        * to the nearest word boundary on both start and end */
+                       res = target_write_memory(bank->target, address, 4, nw, pb + pg_offset);
+               } else {
+                       assert(nb % 4 == 0);
+                       nw = nb / 4;
+                       assert(pg_offset + 4 * nw <= chip->page_size);
+
+                       /* Word aligned data, use direct write from buffer */
+                       res = target_write_memory(bank->target, address, 4, nw, buffer);
+               }
+               if (res != ERROR_OK) {
+                       LOG_ERROR("%s: %d", __func__, __LINE__);
+                       goto free_pb;
+               }
 
-                       if (res != ERROR_OK)
-                               return res;
+               /* Devices with errata 13134 have automatic page write enabled by default
+                * For other devices issue a write page CMD to the NVM
+                * If the page has not been written up to the last word
+                * then issue CMD_WP always */
+               if (manual_wp || pg_offset + 4 * nw < chip->page_size) {
+                       res = samd_issue_nvmctrl_command(bank->target, SAMD_NVM_CMD_WP);
+               } else {
+                       /* Access through AHB is stalled while flash is being programmed */
+                       usleep(200);
+
+                       res = samd_check_error(bank->target);
                }
+
+               if (res != ERROR_OK) {
+                       LOG_ERROR("%s: write failed at address 0x%08" PRIx32, __func__, address);
+                       goto free_pb;
+               }
+
+               /* We're done with the page contents */
+               count -= nb;
+               offset += nb;
+               buffer += nb;
        }
 
-       return ERROR_OK;
+free_pb:
+       if (pb)
+               free(pb);
+
+       return res;
 }
 
 FLASH_BANK_COMMAND_HANDLER(samd_flash_bank_command)
@@ -685,18 +845,23 @@ COMMAND_HANDLER(samd_handle_info_command)
 COMMAND_HANDLER(samd_handle_chip_erase_command)
 {
        struct target *target = get_current_target(CMD_CTX);
+       int res = ERROR_FAIL;
 
        if (target) {
                /* Enable access to the DSU by disabling the write protect bit */
                target_write_u32(target, SAMD_PAC1, (1<<1));
+               /* intentionally without error checking - not accessible on secured chip */
+
                /* Tell the DSU to perform a full chip erase.  It takes about 240ms to
                 * perform the erase. */
-               target_write_u8(target, SAMD_DSU, (1<<4));
-
-               command_print(CMD_CTX, "chip erased");
+               res = target_write_u8(target, SAMD_DSU + SAMD_DSU_CTRL_EXT, (1<<4));
+               if (res == ERROR_OK)
+                       command_print(CMD_CTX, "chip erase started");
+               else
+                       command_print(CMD_CTX, "write to DSU CTRL failed");
        }
 
-       return ERROR_OK;
+       return res;
 }
 
 COMMAND_HANDLER(samd_handle_set_security_command)
@@ -727,7 +892,165 @@ COMMAND_HANDLER(samd_handle_set_security_command)
        return res;
 }
 
+COMMAND_HANDLER(samd_handle_eeprom_command)
+{
+       int res = ERROR_OK;
+       struct target *target = get_current_target(CMD_CTX);
+
+       if (target) {
+               if (target->state != TARGET_HALTED) {
+                       LOG_ERROR("Target not halted");
+                       return ERROR_TARGET_NOT_HALTED;
+               }
+
+               if (CMD_ARGC >= 1) {
+                       int val = atoi(CMD_ARGV[0]);
+                       uint32_t code;
+
+                       if (val == 0)
+                               code = 7;
+                       else {
+                               /* Try to match size in bytes with corresponding size code */
+                               for (code = 0; code <= 6; code++) {
+                                       if (val == (2 << (13 - code)))
+                                               break;
+                               }
+
+                               if (code > 6) {
+                                       command_print(CMD_CTX, "Invalid EEPROM size.  Please see "
+                                                       "datasheet for a list valid sizes.");
+                                       return ERROR_COMMAND_SYNTAX_ERROR;
+                               }
+                       }
+
+                       res = samd_modify_user_row(target, code, 4, 6);
+               } else {
+                       uint16_t val;
+                       res = target_read_u16(target, SAMD_USER_ROW, &val);
+                       if (res == ERROR_OK) {
+                               uint32_t size = ((val >> 4) & 0x7); /* grab size code */
+
+                               if (size == 0x7)
+                                       command_print(CMD_CTX, "EEPROM is disabled");
+                               else {
+                                       /* Otherwise, 6 is 256B, 0 is 16KB */
+                                       command_print(CMD_CTX, "EEPROM size is %u bytes",
+                                                       (2 << (13 - size)));
+                               }
+                       }
+               }
+       }
+
+       return res;
+}
+
+COMMAND_HANDLER(samd_handle_bootloader_command)
+{
+       int res = ERROR_OK;
+       struct target *target = get_current_target(CMD_CTX);
+
+       if (target) {
+               if (target->state != TARGET_HALTED) {
+                       LOG_ERROR("Target not halted");
+                       return ERROR_TARGET_NOT_HALTED;
+               }
+
+               /* Retrieve the MCU's page size, in bytes. */
+               uint32_t page_size;
+               res = samd_get_flash_page_info(target, &page_size, NULL);
+               if (res != ERROR_OK) {
+                       LOG_ERROR("Couldn't determine Flash page size");
+                       return res;
+               }
+
+               if (CMD_ARGC >= 1) {
+                       int val = atoi(CMD_ARGV[0]);
+                       uint32_t code;
+
+                       if (val == 0)
+                               code = 7;
+                       else {
+                               /* Try to match size in bytes with corresponding size code */
+                               for (code = 0; code <= 6; code++) {
+                                       if ((unsigned int)val == (2UL << (8UL - code)) * page_size)
+                                               break;
+                               }
+
+                               if (code > 6) {
+                                       command_print(CMD_CTX, "Invalid bootloader size.  Please "
+                                                       "see datasheet for a list valid sizes.");
+                                       return ERROR_COMMAND_SYNTAX_ERROR;
+                               }
+
+                       }
+
+                       res = samd_modify_user_row(target, code, 0, 2);
+               } else {
+                       uint16_t val;
+                       res = target_read_u16(target, SAMD_USER_ROW, &val);
+                       if (res == ERROR_OK) {
+                               uint32_t size = (val & 0x7); /* grab size code */
+                               uint32_t nb;
+
+                               if (size == 0x7)
+                                       nb = 0;
+                               else
+                                       nb = (2 << (8 - size)) * page_size;
+
+                               /* There are 4 pages per row */
+                               command_print(CMD_CTX, "Bootloader size is %" PRIu32 " bytes (%" PRIu32 " rows)",
+                                          nb, (uint32_t)(nb / (page_size * 4)));
+                       }
+               }
+       }
+
+       return res;
+}
+
+
+
+COMMAND_HANDLER(samd_handle_reset_deassert)
+{
+       struct target *target = get_current_target(CMD_CTX);
+       int retval = ERROR_OK;
+       enum reset_types jtag_reset_config = jtag_get_reset_config();
+
+       /* If the target has been unresponsive before, try to re-establish
+        * communication now - CPU is held in reset by DSU, DAP is working */
+       if (!target_was_examined(target))
+               target_examine_one(target);
+       target_poll(target);
+
+       /* In case of sysresetreq, debug retains state set in cortex_m_assert_reset()
+        * so we just release reset held by DSU
+        *
+        * n_RESET (srst) clears the DP, so reenable debug and set vector catch here
+        *
+        * After vectreset DSU release is not needed however makes no harm
+        */
+       if (target->reset_halt && (jtag_reset_config & RESET_HAS_SRST)) {
+               retval = target_write_u32(target, DCB_DHCSR, DBGKEY | C_HALT | C_DEBUGEN);
+               if (retval == ERROR_OK)
+                       retval = target_write_u32(target, DCB_DEMCR,
+                               TRCENA | VC_HARDERR | VC_BUSERR | VC_CORERESET);
+               /* do not return on error here, releasing DSU reset is more important */
+       }
+
+       /* clear CPU Reset Phase Extension bit */
+       int retval2 = target_write_u8(target, SAMD_DSU + SAMD_DSU_STATUSA, (1<<1));
+       if (retval2 != ERROR_OK)
+               return retval2;
+
+       return retval;
+}
+
 static const struct command_registration at91samd_exec_command_handlers[] = {
+       {
+               .name = "dsu_reset_deassert",
+               .handler = samd_handle_reset_deassert,
+               .mode = COMMAND_EXEC,
+               .help = "deasert internal reset held by DSU"
+       },
        {
                .name = "info",
                .handler = samd_handle_info_command,
@@ -751,6 +1074,26 @@ static const struct command_registration at91samd_exec_command_handlers[] = {
                        "The only way to undo this is to issue the chip-erase"
                        "command.",
        },
+       {
+               .name = "eeprom",
+               .usage = "[size_in_bytes]",
+               .handler = samd_handle_eeprom_command,
+               .mode = COMMAND_EXEC,
+               .help = "Show or set the EEPROM size setting, stored in the User Row."
+                       "Please see Table 20-3 of the SAMD20 datasheet for allowed values."
+                       "Changes are stored immediately but take affect after the MCU is"
+                       "reset.",
+       },
+       {
+               .name = "bootloader",
+               .usage = "[size_in_bytes]",
+               .handler = samd_handle_bootloader_command,
+               .mode = COMMAND_EXEC,
+               .help = "Show or set the bootloader size, stored in the User Row."
+                       "Please see Table 20-2 of the SAMD20 datasheet for allowed values."
+                       "Changes are stored immediately but take affect after the MCU is"
+                       "reset.",
+       },
        COMMAND_REGISTRATION_DONE
 };