at91samd: add chip IDs for SAMC20 and SAMC21 families

[openocd.git] / src / flash / nor / at91samd.c

/***************************************************************************
 *   Copyright (C) 2013 by Andrey Yurovsky                                 *
 *   Andrey Yurovsky <yurovsky@gmail.com>                                  *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   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.           *
 ***************************************************************************/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "imp.h"
#include "helper/binarybuffer.h"

#define SAMD_NUM_SECTORS        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_DID            0x18            /* Device ID register */

#define SAMD_NVMCTRL_CTRLA              0x00    /* NVM control A register */
#define SAMD_NVMCTRL_CTRLB              0x04    /* NVM control B register */
#define SAMD_NVMCTRL_PARAM              0x08    /* NVM parameters register */
#define SAMD_NVMCTRL_INTFLAG    0x18    /* NVM Interupt Flag Status & Clear */
#define SAMD_NVMCTRL_STATUS             0x18    /* NVM status register */
#define SAMD_NVMCTRL_ADDR               0x1C    /* NVM address register */
#define SAMD_NVMCTRL_LOCK               0x20    /* NVM Lock section register */

#define SAMD_CMDEX_KEY          0xA5UL
#define SAMD_NVM_CMD(n)         ((SAMD_CMDEX_KEY << 8) | (n & 0x7F))

/* NVMCTRL commands.  See Table 20-4 in 42129F–SAM–10/2013 */
#define SAMD_NVM_CMD_ER         0x02            /* Erase Row */
#define SAMD_NVM_CMD_WP         0x04            /* Write Page */
#define SAMD_NVM_CMD_EAR        0x05            /* Erase Auxilary Row */
#define SAMD_NVM_CMD_WAP        0x06            /* Write Auxilary Page */
#define SAMD_NVM_CMD_LR         0x40            /* Lock Region */
#define SAMD_NVM_CMD_UR         0x41            /* Unlock Region */
#define SAMD_NVM_CMD_SPRM       0x42            /* Set Power Reduction Mode */
#define SAMD_NVM_CMD_CPRM       0x43            /* Clear Power Reduction Mode */
#define SAMD_NVM_CMD_PBC        0x44            /* Page Buffer Clear */
#define SAMD_NVM_CMD_SSB        0x45            /* Set Security Bit */
#define SAMD_NVM_CMD_INVALL     0x46            /* Invalidate all caches */

/* 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_10          0x02
#define SAMD_SERIES_11          0x03

struct samd_part {
        uint8_t id;
        const char *name;
        uint32_t flash_kb;
        uint32_t ram_kb;
};

/* Known SAMD10 parts */
static const struct samd_part samd10_parts[] = {
        { 0x0, "SAMD10D14AMU", 16, 4 },
        { 0x1, "SAMD10D13AMU", 8, 4 },
        { 0x2, "SAMD10D12AMU", 4, 4 },
        { 0x3, "SAMD10D14ASU", 16, 4 },
        { 0x4, "SAMD10D13ASU", 8, 4 },
        { 0x5, "SAMD10D12ASU", 4, 4 },
        { 0x6, "SAMD10C14A", 16, 4 },
        { 0x7, "SAMD10C13A", 8, 4 },
        { 0x8, "SAMD10C12A", 4, 4 },
};

/* Known SAMD11 parts */
static const struct samd_part samd11_parts[] = {
        { 0x0, "SAMD11D14AMU", 16, 4 },
        { 0x1, "SAMD11D13AMU", 8, 4 },
        { 0x2, "SAMD11D12AMU", 4, 4 },
        { 0x3, "SAMD11D14ASU", 16, 4 },
        { 0x4, "SAMD11D13ASU", 8, 4 },
        { 0x5, "SAMD11D12ASU", 4, 4 },
        { 0x6, "SAMD11C14A", 16, 4 },
        { 0x7, "SAMD11C13A", 8, 4 },
        { 0x8, "SAMD11C12A", 4, 4 },
};

/* Known SAMD20 parts. See Table 12-8 in 42129F–SAM–10/2013 */
static const struct samd_part samd20_parts[] = {
        { 0x0, "SAMD20J18A", 256, 32 },
        { 0x1, "SAMD20J17A", 128, 16 },
        { 0x2, "SAMD20J16A", 64, 8 },
        { 0x3, "SAMD20J15A", 32, 4 },
        { 0x4, "SAMD20J14A", 16, 2 },
        { 0x5, "SAMD20G18A", 256, 32 },
        { 0x6, "SAMD20G17A", 128, 16 },
        { 0x7, "SAMD20G16A", 64, 8 },
        { 0x8, "SAMD20G15A", 32, 4 },
        { 0x9, "SAMD20G14A", 16, 2 },
        { 0xA, "SAMD20E18A", 256, 32 },
        { 0xB, "SAMD20E17A", 128, 16 },
        { 0xC, "SAMD20E16A", 64, 8 },
        { 0xD, "SAMD20E15A", 32, 4 },
        { 0xE, "SAMD20E14A", 16, 2 },
};

/* Known SAMD21 parts. */
static const struct samd_part samd21_parts[] = {
        { 0x0, "SAMD21J18A", 256, 32 },
        { 0x1, "SAMD21J17A", 128, 16 },
        { 0x2, "SAMD21J16A", 64, 8 },
        { 0x3, "SAMD21J15A", 32, 4 },
        { 0x4, "SAMD21J14A", 16, 2 },
        { 0x5, "SAMD21G18A", 256, 32 },
        { 0x6, "SAMD21G17A", 128, 16 },
        { 0x7, "SAMD21G16A", 64, 8 },
        { 0x8, "SAMD21G15A", 32, 4 },
        { 0x9, "SAMD21G14A", 16, 2 },
        { 0xA, "SAMD21E18A", 256, 32 },
        { 0xB, "SAMD21E17A", 128, 16 },
        { 0xC, "SAMD21E16A", 64, 8 },
        { 0xD, "SAMD21E15A", 32, 4 },
        { 0xE, "SAMD21E14A", 16, 2 },
};

/* Known SAMR21 parts. */
static const struct samd_part samr21_parts[] = {
        { 0x19, "SAMR21G18A", 256, 32 },
        { 0x1A, "SAMR21G17A", 128, 32 },
        { 0x1B, "SAMR21G16A",  64, 32 },
        { 0x1C, "SAMR21E18A", 256, 32 },
        { 0x1D, "SAMR21E17A", 128, 32 },
        { 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 },
};

/* 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
 * family this is and then we can use the corresponding table. */
struct samd_family {
        uint8_t processor;
        uint8_t family;
        uint8_t series;
        const struct samd_part *parts;
        size_t num_parts;
};

/* Known SAMD families */
static const struct samd_family samd_families[] = {
        { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_20,
                samd20_parts, ARRAY_SIZE(samd20_parts) },
        { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_21,
                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_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_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;

        bool probed;
        struct target *target;
        struct samd_info *next;
};

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 >> 23) & 0x1F;
        uint8_t series = (id >> 16) & 0x3F;
        uint8_t devsel = id & 0xFF;

        for (unsigned i = 0; i < ARRAY_SIZE(samd_families); i++) {
                if (samd_families[i].processor == processor &&
                        samd_families[i].series == series &&
                        samd_families[i].family == family) {
                        for (unsigned j = 0; j < samd_families[i].num_parts; j++) {
                                if (samd_families[i].parts[j].id == devsel)
                                        return &samd_families[i].parts[j];
                        }
                }
        }

        return NULL;
}

static int samd_protect_check(struct flash_bank *bank)
{
        int res;
        uint16_t lock;

        res = target_read_u16(bank->target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_LOCK, &lock);
        if (res != ERROR_OK)
                return res;

        /* Lock bits are active-low */
        for (int i = 0; i < bank->num_sectors; i++)
                bank->sectors[i].is_protected = !(lock & (1<<i));

        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;
        int res;
        struct samd_info *chip = (struct samd_info *)bank->driver_priv;
        const struct samd_part *part;

        if (chip->probed)
                return ERROR_OK;

        res = target_read_u32(bank->target, SAMD_DSU + SAMD_DSU_DID, &id);
        if (res != ERROR_OK) {
                LOG_ERROR("Couldn't read Device ID register");
                return res;
        }

        part = samd_find_part(id);
        if (part == NULL) {
                LOG_ERROR("Couldn't find part correspoding to DID %08" PRIx32, id);
                return ERROR_FAIL;
        }

        bank->size = part->flash_kb * 1024;

        chip->sector_size = bank->size / SAMD_NUM_SECTORS;

        res = samd_get_flash_page_info(bank->target, &chip->page_size,
                        &chip->num_pages);
        if (res != ERROR_OK) {
                LOG_ERROR("Couldn't determine Flash page size");
                return res;
        }

        /* 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) {
                LOG_WARNING("SAMD: bank size doesn't match NVM parameters. "
                                "Identified %" PRIu32 "KB Flash but NVMCTRL reports %u %" PRIu32 "B pages",
                                part->flash_kb, chip->num_pages, chip->page_size);
        }

        /* Allocate the sector table */
        bank->num_sectors = SAMD_NUM_SECTORS;
        bank->sectors = calloc(bank->num_sectors, sizeof((bank->sectors)[0]));
        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;
        }

        samd_protect_check(bank);

        /* Done */
        chip->probed = true;

        LOG_INFO("SAMD MCU: %s (%" PRIu32 "KB Flash, %" PRIu32 "KB RAM)", part->name,
                        part->flash_kb, part->ram_kb);

        return ERROR_OK;
}

static bool samd_check_error(struct target *target)
{
        int ret;
        bool error;
        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;
        }

        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");

                error = true;
        } else {
                error = false;
        }

        /* Clear the error conditions by writing a one to them */
        ret = target_write_u16(target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_STATUS, status);
        if (ret != ERROR_OK)
                LOG_ERROR("Can't clear NVM error conditions");

        return error;
}

static int samd_issue_nvmctrl_command(struct target *target, uint16_t cmd)
{
        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,
                        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_erase_row(struct target *target, uint32_t address)
{
        int res;

        /* Set an address contained in the row to be erased */
        res = target_write_u32(target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_ADDR, address >> 1);

        /* Issue the Erase Row command to erase that row. */
        if (res == ERROR_OK)
                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);
                return ERROR_FAIL;
        }

        return ERROR_OK;
}

static bool is_user_row_reserved_bit(uint8_t bit)
{
        /* 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;
        }

        return false;
}

/* 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;

        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;
        }

        /* 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;
        }

        /* Make sure the size is sane before we allocate. */
        assert(page_size > 0 && page_size <= SAMD_PAGE_SIZE_MAX);

        /* 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;
        }

        uint8_t *buf = malloc(page_size);
        if (!buf)
                return ERROR_FAIL;

        /* Read the user row (comprising one page) by half-words. */
        res = target_read_memory(target, SAMD_USER_ROW, 2, page_size / 2, 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;
                }
        }

        /* Modify */
        buf_set_u32(buf, startb, endb - startb + 1, value);

        /* Write the page buffer back out to the target.  A Flash write will be
         * triggered automatically. */
        res = target_write_memory(target, SAMD_USER_ROW, 4, page_size / 4, buf);
        if (res != ERROR_OK)
                goto out_user_row;

        if (samd_check_error(target)) {
                res = ERROR_FAIL;
                goto out_user_row;
        }

        /* Success */
        res = ERROR_OK;

out_user_row:
        free(buf);

        return res;
}

static int samd_protect(struct flash_bank *bank, int set, int first, int last)
{
        struct samd_info *chip = (struct samd_info *)bank->driver_priv;

        /* 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;
        }

        int 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) >> 1));
                        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;
                }
        }

        /* 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, correspoding 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. */

        res = samd_modify_user_row(bank->target, set ? 0x0000 : 0xFFFF,
                        48 + first, 48 + last);
        if (res != ERROR_OK)
                LOG_WARNING("SAMD: protect settings were not made persistent!");

        res = ERROR_OK;

exit:
        samd_protect_check(bank);

        return res;
}

static int samd_erase(struct flash_bank *bank, int first, int last)
{
        int res;
        int rows_in_sector;
        struct samd_info *chip = (struct samd_info *)bank->driver_priv;

        if (bank->target->state != TARGET_HALTED) {
                LOG_ERROR("Target not halted");

                return ERROR_TARGET_NOT_HALTED;
        }

        if (!chip->probed) {
                if (samd_probe(bank) != ERROR_OK)
                        return ERROR_FLASH_BANK_NOT_PROBED;
        }

        /* 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);

        /* 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;
                }

                if (bank->sectors[s].is_erased != 1) {
                        /* 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->target, r * chip->page_size * 4);
                                if (res != ERROR_OK) {
                                        LOG_ERROR("SAMD: failed to erase sector %d", s);
                                        return res;
                                }
                        }

                        bank->sectors[s].is_erased = 1;
                }
        }

        return ERROR_OK;
}

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;

        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];
        }
        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;

        struct flash_sector *sector = samd_find_sector_by_address(bank, address);

        if (!sector) {
                LOG_ERROR("Can't find sector corresponding to address 0x%08" PRIx32, address);
                return ERROR_FLASH_OPERATION_FAILED;
        }

        if (sector->is_protected) {
                LOG_ERROR("Trying to write to a protected sector at 0x%08" PRIx32, address);
                return ERROR_FLASH_OPERATION_FAILED;
        }

        /* Erase the row that we'll be writing to */
        res = samd_erase_row(bank->target, address);
        if (res != ERROR_OK)
                return res;

        /* Now write the pages in this row. */
        for (unsigned int i = 0; i < 4; i++) {
                bool error;

                /* 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;
                }

                /* Access through AHB is stalled while flash is being programmed */
                usleep(200);

                error = samd_check_error(bank->target);
                if (error)
                        return ERROR_FAIL;

                /* Next page */
                address += chip->page_size;
                buf += chip->page_size;
        }

        sector->is_erased = 0;

        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)
{
        int res;
        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);

        /* 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;
        }

        /* Insert our partial row over the data from Flash */
        memcpy(rb + (row_offset % row_size), buf, nb);

        /* Write the row back out */
        res = samd_write_row(bank, address, rb);
        free(rb);

        return res;
}

static int samd_write(struct flash_bank *bank, const uint8_t *buffer,
                uint32_t offset, uint32_t count)
{
        int res;
        uint32_t address;
        uint32_t nb = 0;
        struct samd_info *chip = (struct samd_info *)bank->driver_priv;
        uint32_t row_size = chip->page_size * 4;

        if (bank->target->state != TARGET_HALTED) {
                LOG_ERROR("Target not halted");

                return ERROR_TARGET_NOT_HALTED;
        }

        if (!chip->probed) {
                if (samd_probe(bank) != ERROR_OK)
                        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;
        }

        address = (offset / row_size) * row_size + bank->base;

        if (nb > 0) {
                res = samd_write_row_partial(bank, address, buffer,
                                offset % row_size, nb);
                if (res != ERROR_OK)
                        return res;

                /* 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;
                        }

                        r++;

                        if (res != ERROR_OK)
                                return res;
                }
        }

        return ERROR_OK;
}

FLASH_BANK_COMMAND_HANDLER(samd_flash_bank_command)
{
        struct samd_info *chip = samd_chips;

        while (chip) {
                if (chip->target == bank->target)
                        break;
                chip = chip->next;
        }

        if (!chip) {
                /* Create a new chip */
                chip = calloc(1, sizeof(*chip));
                if (!chip)
                        return ERROR_FAIL;

                chip->target = bank->target;
                chip->probed = false;

                bank->driver_priv = chip;

                /* Insert it into the chips list (at head) */
                chip->next = samd_chips;
                samd_chips = chip;
        }

        if (bank->base != SAMD_FLASH) {
                LOG_ERROR("Address 0x%08" PRIx32 " invalid bank address (try 0x%08" PRIx32
                                "[at91samd series] )",
                                bank->base, SAMD_FLASH);
                return ERROR_FAIL;
        }

        return ERROR_OK;
}

COMMAND_HANDLER(samd_handle_info_command)
{
        return ERROR_OK;
}

COMMAND_HANDLER(samd_handle_chip_erase_command)
{
        struct target *target = get_current_target(CMD_CTX);

        if (target) {
                /* Enable access to the DSU by disabling the write protect bit */
                target_write_u32(target, SAMD_PAC1, (1<<1));
                /* 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");
        }

        return ERROR_OK;
}

COMMAND_HANDLER(samd_handle_set_security_command)
{
        int res = ERROR_OK;
        struct target *target = get_current_target(CMD_CTX);

        if (CMD_ARGC < 1 || (CMD_ARGC >= 1 && (strcmp(CMD_ARGV[0], "enable")))) {
                command_print(CMD_CTX, "supply the \"enable\" argument to proceed.");
                return ERROR_COMMAND_SYNTAX_ERROR;
        }

        if (target) {
                if (target->state != TARGET_HALTED) {
                        LOG_ERROR("Target not halted");
                        return ERROR_TARGET_NOT_HALTED;
                }

                res = samd_issue_nvmctrl_command(target, SAMD_NVM_CMD_SSB);

                /* Check (and clear) error conditions */
                if (res == ERROR_OK)
                        command_print(CMD_CTX, "chip secured on next power-cycle");
                else
                        command_print(CMD_CTX, "failed to secure chip");
        }

        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;
}

static const struct command_registration at91samd_exec_command_handlers[] = {
        {
                .name = "info",
                .handler = samd_handle_info_command,
                .mode = COMMAND_EXEC,
                .help = "Print information about the current at91samd chip"
                        "and its flash configuration.",
        },
        {
                .name = "chip-erase",
                .handler = samd_handle_chip_erase_command,
                .mode = COMMAND_EXEC,
                .help = "Erase the entire Flash by using the Chip"
                        "Erase feature in the Device Service Unit (DSU).",
        },
        {
                .name = "set-security",
                .handler = samd_handle_set_security_command,
                .mode = COMMAND_EXEC,
                .help = "Secure the chip's Flash by setting the Security Bit."
                        "This makes it impossible to read the Flash contents."
                        "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
};

static const struct command_registration at91samd_command_handlers[] = {
        {
                .name = "at91samd",
                .mode = COMMAND_ANY,
                .help = "at91samd flash command group",
                .usage = "",
                .chain = at91samd_exec_command_handlers,
        },
        COMMAND_REGISTRATION_DONE
};

struct flash_driver at91samd_flash = {
        .name = "at91samd",
        .commands = at91samd_command_handlers,
        .flash_bank_command = samd_flash_bank_command,
        .erase = samd_erase,
        .protect = samd_protect,
        .write = samd_write,
        .read = default_flash_read,
        .probe = samd_probe,
        .auto_probe = samd_probe,
        .erase_check = default_flash_blank_check,
        .protect_check = samd_protect_check,
};