bcm2835gpio.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
/***************************************************************************
 *   Copyright (C) 2013 by Paul Fertser, fercerpav@gmail.com               *
 *                                                                         *
 *   Copyright (C) 2012 by Creative Product Design, marc @ cpdesign.com.au *
 *   Based on at91rm9200.c (c) Anders Larsen                               *
 *   and RPi GPIO examples by Gert van Loo & Dom                           *
 ***************************************************************************/
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include <jtag/adapter.h>
#include <jtag/interface.h>
#include <transport/transport.h>
#include "bitbang.h"
 
#include <sys/mman.h>
 
static char *bcm2835_peri_mem_dev;
static off_t bcm2835_peri_base = 0x20000000;
#define BCM2835_GPIO_BASE   (bcm2835_peri_base + 0x200000) /* GPIO controller */
 
#define BCM2835_PADS_GPIO_0_27      (bcm2835_peri_base + 0x100000)
#define BCM2835_PADS_GPIO_0_27_OFFSET   (0x2c / 4)
 
/* See "GPIO Function Select Registers (GPFSELn)" in "Broadcom BCM2835 ARM Peripherals" datasheet. */
#define BCM2835_GPIO_MODE_INPUT 0
#define BCM2835_GPIO_MODE_OUTPUT 1
 
/* GPIO setup macros */
#define MODE_GPIO(_g) ({                                   \
    typeof(_g) g = (_g);                                   \
    *(pio_base + (g / 10)) >> ((g % 10) * 3) & 7;          \
})
 
#define INP_GPIO(_g) do {                                  \
    typeof(_g) g1 = (_g);                                  \
    *(pio_base + (g1 / 10)) &= ~(7 << ((g1 % 10) * 3));    \
} while (0)
 
#define SET_MODE_GPIO(_g, m) do {                          \
    typeof(_g) g = (_g);                                   \
    /* clear the mode bits first, then set as necessary */ \
    INP_GPIO(g);                                           \
    *(pio_base + (g / 10)) |= ((m) << ((g % 10) * 3));     \
} while (0)
 
#define OUT_GPIO(g) SET_MODE_GPIO(g, BCM2835_GPIO_MODE_OUTPUT)
 
#define GPIO_SET (*(pio_base + 7))  /* sets   bits which are 1, ignores bits which are 0 */
#define GPIO_CLR (*(pio_base + 10)) /* clears bits which are 1, ignores bits which are 0 */
#define GPIO_LEV (*(pio_base + 13)) /* current level of the pin */
 
static int dev_mem_fd;
static volatile uint32_t *pio_base = MAP_FAILED;
static volatile uint32_t *pads_base = MAP_FAILED;
 
/* Transition delay coefficients */
static int speed_coeff = 113714;
static int speed_offset = 28;
static unsigned int jtag_delay;
 
static const struct adapter_gpio_config *adapter_gpio_config;
static struct initial_gpio_state {
    unsigned int mode;
    unsigned int output_level;
} initial_gpio_state[ADAPTER_GPIO_IDX_NUM];
static uint32_t initial_drive_strength_etc;
 
static inline const char *bcm2835_get_mem_dev(void)
{
    if (bcm2835_peri_mem_dev)
        return bcm2835_peri_mem_dev;
 
    return "/dev/gpiomem";
}
 
static inline void bcm2835_gpio_synchronize(void)
{
    /* Ensure that previous writes to GPIO registers are flushed out of
     * the inner shareable domain to prevent pipelined writes to the
     * same address being merged.
     */
    __sync_synchronize();
}
 
static inline void bcm2835_delay(void)
{
    for (unsigned int i = 0; i < jtag_delay; i++)
        asm volatile ("");
}
 
static bool is_gpio_config_valid(enum adapter_gpio_config_index idx)
{
    /* Only chip 0 is supported, accept unset value (-1) too */
    return adapter_gpio_config[idx].gpio_num <= 31;
}
 
static void set_gpio_value(const struct adapter_gpio_config *gpio_config, int value)
{
    value = value ^ (gpio_config->active_low ? 1 : 0);
    switch (gpio_config->drive) {
    case ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL:
        if (value)
            GPIO_SET = 1 << gpio_config->gpio_num;
        else
            GPIO_CLR = 1 << gpio_config->gpio_num;
        /* For performance reasons assume the GPIO is already set as an output
         * and therefore the call can be omitted here.
         */
        break;
    case ADAPTER_GPIO_DRIVE_MODE_OPEN_DRAIN:
        if (value) {
            INP_GPIO(gpio_config->gpio_num);
        } else {
            GPIO_CLR = 1 << gpio_config->gpio_num;
            OUT_GPIO(gpio_config->gpio_num);
        }
        break;
    case ADAPTER_GPIO_DRIVE_MODE_OPEN_SOURCE:
        if (value) {
            GPIO_SET = 1 << gpio_config->gpio_num;
            OUT_GPIO(gpio_config->gpio_num);
        } else {
            INP_GPIO(gpio_config->gpio_num);
        }
        break;
    }
    bcm2835_gpio_synchronize();
}
 
static void restore_gpio(enum adapter_gpio_config_index idx)
{
    if (is_gpio_config_valid(idx)) {
        SET_MODE_GPIO(adapter_gpio_config[idx].gpio_num, initial_gpio_state[idx].mode);
        if (initial_gpio_state[idx].mode == BCM2835_GPIO_MODE_OUTPUT) {
            if (initial_gpio_state[idx].output_level)
                GPIO_SET = 1 << adapter_gpio_config[idx].gpio_num;
            else
                GPIO_CLR = 1 << adapter_gpio_config[idx].gpio_num;
        }
    }
    bcm2835_gpio_synchronize();
}
 
static void initialize_gpio(enum adapter_gpio_config_index idx)
{
    if (!is_gpio_config_valid(idx))
        return;
 
    initial_gpio_state[idx].mode = MODE_GPIO(adapter_gpio_config[idx].gpio_num);
    unsigned int shift = adapter_gpio_config[idx].gpio_num;
    initial_gpio_state[idx].output_level = (GPIO_LEV >> shift) & 1;
    LOG_DEBUG("saved GPIO mode for %s (GPIO %d %d): %d",
            adapter_gpio_get_name(idx), adapter_gpio_config[idx].chip_num, adapter_gpio_config[idx].gpio_num,
            initial_gpio_state[idx].mode);
 
    if (adapter_gpio_config[idx].pull != ADAPTER_GPIO_PULL_NONE) {
        LOG_WARNING("BCM2835 GPIO does not support pull-up or pull-down settings (signal %s)",
            adapter_gpio_get_name(idx));
    }
 
    switch (adapter_gpio_config[idx].init_state) {
    case ADAPTER_GPIO_INIT_STATE_INACTIVE:
        set_gpio_value(&adapter_gpio_config[idx], 0);
        break;
    case ADAPTER_GPIO_INIT_STATE_ACTIVE:
        set_gpio_value(&adapter_gpio_config[idx], 1);
        break;
    case ADAPTER_GPIO_INIT_STATE_INPUT:
        INP_GPIO(adapter_gpio_config[idx].gpio_num);
        break;
    }
 
    /* Direction for non push-pull is already set by set_gpio_value() */
    if (adapter_gpio_config[idx].drive == ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL
        && adapter_gpio_config[idx].init_state != ADAPTER_GPIO_INIT_STATE_INPUT)
        OUT_GPIO(adapter_gpio_config[idx].gpio_num);
    bcm2835_gpio_synchronize();
}
 
static bb_value_t bcm2835gpio_read(void)
{
    unsigned int shift = adapter_gpio_config[ADAPTER_GPIO_IDX_TDO].gpio_num;
    uint32_t value = (GPIO_LEV >> shift) & 1;
    return value ^ (adapter_gpio_config[ADAPTER_GPIO_IDX_TDO].active_low ? BB_HIGH : BB_LOW);
}
 
static int bcm2835gpio_write(int tck, int tms, int tdi)
{
    uint32_t set = tck << adapter_gpio_config[ADAPTER_GPIO_IDX_TCK].gpio_num |
            tms << adapter_gpio_config[ADAPTER_GPIO_IDX_TMS].gpio_num |
            tdi << adapter_gpio_config[ADAPTER_GPIO_IDX_TDI].gpio_num;
    uint32_t clear = !tck << adapter_gpio_config[ADAPTER_GPIO_IDX_TCK].gpio_num |
            !tms << adapter_gpio_config[ADAPTER_GPIO_IDX_TMS].gpio_num |
            !tdi << adapter_gpio_config[ADAPTER_GPIO_IDX_TDI].gpio_num;
 
    GPIO_SET = set;
    GPIO_CLR = clear;
    bcm2835_gpio_synchronize();
 
    bcm2835_delay();
 
    return ERROR_OK;
}
 
/* Requires push-pull drive mode for swclk and swdio */
static int bcm2835gpio_swd_write_fast(int swclk, int swdio)
{
    swclk = swclk ^ (adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK].active_low ? 1 : 0);
    swdio = swdio ^ (adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].active_low ? 1 : 0);
 
    uint32_t set = swclk << adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK].gpio_num |
                    swdio << adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num;
    uint32_t clear = !swclk << adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK].gpio_num |
                    !swdio << adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num;
 
    GPIO_SET = set;
    GPIO_CLR = clear;
    bcm2835_gpio_synchronize();
 
    bcm2835_delay();
 
    return ERROR_OK;
}
 
/* Generic mode that works for open-drain/open-source drive modes, but slower */
static int bcm2835gpio_swd_write_generic(int swclk, int swdio)
{
    set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO], swdio);
    set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK], swclk); /* Write clock last */
 
    bcm2835_delay();
 
    return ERROR_OK;
}
 
/* (1) assert or (0) deassert reset lines */
static int bcm2835gpio_reset(int trst, int srst)
{
    /* As the "adapter reset_config" command keeps the srst and trst gpio drive
     * mode settings in sync we can use our standard set_gpio_value() function
     * that honours drive mode and active low.
     */
    if (is_gpio_config_valid(ADAPTER_GPIO_IDX_SRST))
        set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SRST], srst);
 
    if (is_gpio_config_valid(ADAPTER_GPIO_IDX_TRST))
        set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_TRST], trst);
 
    LOG_DEBUG("trst %d gpio: %d %d, srst %d gpio: %d %d",
        trst,
        (int)adapter_gpio_config[ADAPTER_GPIO_IDX_TRST].chip_num,
        (int)adapter_gpio_config[ADAPTER_GPIO_IDX_TRST].gpio_num,
        srst,
        (int)adapter_gpio_config[ADAPTER_GPIO_IDX_SRST].chip_num,
        (int)adapter_gpio_config[ADAPTER_GPIO_IDX_SRST].gpio_num);
    return ERROR_OK;
}
 
static void bcm2835_swdio_drive(bool is_output)
{
    if (is_output) {
        if (is_gpio_config_valid(ADAPTER_GPIO_IDX_SWDIO_DIR))
            set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO_DIR], 1);
        OUT_GPIO(adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num);
    } else {
        INP_GPIO(adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num);
        if (is_gpio_config_valid(ADAPTER_GPIO_IDX_SWDIO_DIR))
            set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO_DIR], 0);
    }
    bcm2835_gpio_synchronize();
}
 
static int bcm2835_swdio_read(void)
{
    unsigned int shift = adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num;
    uint32_t value = (GPIO_LEV >> shift) & 1;
    return value ^ (adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].active_low ? 1 : 0);
}
 
static int bcm2835gpio_khz(int khz, int *jtag_speed)
{
    if (!khz) {
        LOG_DEBUG("BCM2835 GPIO: RCLK not supported");
        return ERROR_FAIL;
    }
    *jtag_speed = DIV_ROUND_UP(speed_coeff, khz) - speed_offset;
    LOG_DEBUG("jtag_delay %d", *jtag_speed);
    if (*jtag_speed < 0)
        *jtag_speed = 0;
    return ERROR_OK;
}
 
static int bcm2835gpio_speed_div(int speed, int *khz)
{
    int divisor = speed + speed_offset;
    /* divide with roundig to the closest */
    *khz = (speed_coeff + divisor / 2) / divisor;
    return ERROR_OK;
}
 
static int bcm2835gpio_speed(int speed)
{
    jtag_delay = speed;
    return ERROR_OK;
}
 
COMMAND_HANDLER(bcm2835gpio_handle_speed_coeffs)
{
    if (CMD_ARGC == 2) {
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], speed_coeff);
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], speed_offset);
    }
 
    command_print(CMD, "BCM2835 GPIO: speed_coeffs = %d, speed_offset = %d",
                  speed_coeff, speed_offset);
    return ERROR_OK;
}
 
COMMAND_HANDLER(bcm2835gpio_handle_peripheral_mem_dev)
{
    if (CMD_ARGC == 1) {
        free(bcm2835_peri_mem_dev);
        bcm2835_peri_mem_dev = strdup(CMD_ARGV[0]);
    }
 
    command_print(CMD, "BCM2835 GPIO: peripheral_mem_dev = %s",
                  bcm2835_get_mem_dev());
    return ERROR_OK;
}
 
COMMAND_HANDLER(bcm2835gpio_handle_peripheral_base)
{
    uint64_t tmp_base;
    if (CMD_ARGC == 1) {
        COMMAND_PARSE_NUMBER(u64, CMD_ARGV[0], tmp_base);
        bcm2835_peri_base = (off_t)tmp_base;
    }
 
    tmp_base = bcm2835_peri_base;
    command_print(CMD, "BCM2835 GPIO: peripheral_base = 0x%08" PRIx64,
                  tmp_base);
    return ERROR_OK;
}
 
static const struct command_registration bcm2835gpio_subcommand_handlers[] = {
    {
        .name = "speed_coeffs",
        .handler = &bcm2835gpio_handle_speed_coeffs,
        .mode = COMMAND_CONFIG,
        .help = "SPEED_COEFF and SPEED_OFFSET for delay calculations.",
        .usage = "[SPEED_COEFF SPEED_OFFSET]",
    },
    {
        .name = "peripheral_mem_dev",
        .handler = &bcm2835gpio_handle_peripheral_mem_dev,
        .mode = COMMAND_CONFIG,
        .help = "device to map memory mapped GPIOs from.",
        .usage = "[device]",
    },
    {
        .name = "peripheral_base",
        .handler = &bcm2835gpio_handle_peripheral_base,
        .mode = COMMAND_CONFIG,
        .help = "peripheral base to access GPIOs, not needed with /dev/gpiomem.",
        .usage = "[base]",
    },
 
    COMMAND_REGISTRATION_DONE
};
 
static const struct command_registration bcm2835gpio_command_handlers[] = {
    {
        .name = "bcm2835gpio",
        .mode = COMMAND_ANY,
        .help = "perform bcm2835gpio management",
        .chain = bcm2835gpio_subcommand_handlers,
        .usage = "",
    },
    COMMAND_REGISTRATION_DONE
};
 
static bool bcm2835gpio_jtag_mode_possible(void)
{
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TCK))
        return false;
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TMS))
        return false;
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TDI))
        return false;
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TDO))
        return false;
    return true;
}
 
static bool bcm2835gpio_swd_mode_possible(void)
{
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_SWCLK))
        return false;
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_SWDIO))
        return false;
    return true;
}
 
static void bcm2835gpio_munmap(void)
{
    if (pio_base != MAP_FAILED) {
        munmap((void *)pio_base, sysconf(_SC_PAGE_SIZE));
        pio_base = MAP_FAILED;
    }
 
    if (pads_base != MAP_FAILED) {
        munmap((void *)pads_base, sysconf(_SC_PAGE_SIZE));
        pads_base = MAP_FAILED;
    }
}
 
static int bcm2835gpio_blink(bool on)
{
    if (is_gpio_config_valid(ADAPTER_GPIO_IDX_LED))
        set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_LED], on ? 1 : 0);
 
    return ERROR_OK;
}
 
static struct bitbang_interface bcm2835gpio_bitbang = {
    .read = bcm2835gpio_read,
    .write = bcm2835gpio_write,
    .swdio_read = bcm2835_swdio_read,
    .swdio_drive = bcm2835_swdio_drive,
    .swd_write = bcm2835gpio_swd_write_generic,
    .blink = bcm2835gpio_blink,
};
 
static int bcm2835gpio_init(void)
{
    LOG_INFO("BCM2835 GPIO JTAG/SWD bitbang driver");
 
    bitbang_interface = &bcm2835gpio_bitbang;
    adapter_gpio_config = adapter_gpio_get_config();
 
    if (transport_is_jtag() && !bcm2835gpio_jtag_mode_possible()) {
        LOG_ERROR("Require tck, tms, tdi and tdo gpios for JTAG mode");
        return ERROR_JTAG_INIT_FAILED;
    }
 
    if (transport_is_swd() && !bcm2835gpio_swd_mode_possible()) {
        LOG_ERROR("Require swclk and swdio gpio for SWD mode");
        return ERROR_JTAG_INIT_FAILED;
    }
 
    bool is_gpiomem = strcmp(bcm2835_get_mem_dev(), "/dev/gpiomem") == 0;
    bool pad_mapping_possible = !is_gpiomem;
 
    dev_mem_fd = open(bcm2835_get_mem_dev(), O_RDWR | O_SYNC);
    if (dev_mem_fd < 0) {
        LOG_ERROR("open %s: %s", bcm2835_get_mem_dev(), strerror(errno));
        /* TODO: add /dev/mem specific doc and refer to it
         * if (!is_gpiomem && (errno == EACCES || errno == EPERM))
         *  LOG_INFO("Consult the user's guide chapter 4.? how to set permissions and capabilities");
         */
        return ERROR_JTAG_INIT_FAILED;
    }
 
    pio_base = mmap(NULL, sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_WRITE,
                MAP_SHARED, dev_mem_fd, BCM2835_GPIO_BASE);
 
    if (pio_base == MAP_FAILED) {
        LOG_ERROR("mmap: %s", strerror(errno));
        close(dev_mem_fd);
        return ERROR_JTAG_INIT_FAILED;
    }
 
    /* TODO: move pads config to a separate utility */
    if (pad_mapping_possible) {
        pads_base = mmap(NULL, sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_WRITE,
                MAP_SHARED, dev_mem_fd, BCM2835_PADS_GPIO_0_27);
 
        if (pads_base == MAP_FAILED) {
            LOG_ERROR("mmap pads: %s", strerror(errno));
            LOG_WARNING("Continuing with unchanged GPIO pad settings (drive strength and slew rate)");
        }
    } else {
        pads_base = MAP_FAILED;
    }
 
    close(dev_mem_fd);
 
    if (pads_base != MAP_FAILED) {
        /* set 4mA drive strength, slew rate limited, hysteresis on */
        initial_drive_strength_etc = pads_base[BCM2835_PADS_GPIO_0_27_OFFSET] & 0x1f;
LOG_INFO("initial pads conf %08x", pads_base[BCM2835_PADS_GPIO_0_27_OFFSET]);
        pads_base[BCM2835_PADS_GPIO_0_27_OFFSET] = 0x5a000008 + 1;
LOG_INFO("pads conf set to %08x", pads_base[BCM2835_PADS_GPIO_0_27_OFFSET]);
    }
 
    /* Configure JTAG/SWD signals. Default directions and initial states are handled
     * by adapter.c and "adapter gpio" command.
     */
    if (transport_is_jtag()) {
        initialize_gpio(ADAPTER_GPIO_IDX_TDO);
        initialize_gpio(ADAPTER_GPIO_IDX_TDI);
        initialize_gpio(ADAPTER_GPIO_IDX_TMS);
        initialize_gpio(ADAPTER_GPIO_IDX_TCK);
        initialize_gpio(ADAPTER_GPIO_IDX_TRST);
    }
 
    if (transport_is_swd()) {
        /* swdio and its buffer should be initialized in the order that prevents
         * two outputs from being connected together. This will occur if the
         * swdio GPIO of the AM335x is configured as an output while its
         * external buffer is configured to send the swdio signal from the
         * target to the AM335x.
         */
        if (adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].init_state == ADAPTER_GPIO_INIT_STATE_INPUT) {
            initialize_gpio(ADAPTER_GPIO_IDX_SWDIO);
            initialize_gpio(ADAPTER_GPIO_IDX_SWDIO_DIR);
        } else {
            initialize_gpio(ADAPTER_GPIO_IDX_SWDIO_DIR);
            initialize_gpio(ADAPTER_GPIO_IDX_SWDIO);
        }
 
        initialize_gpio(ADAPTER_GPIO_IDX_SWCLK);
 
        if (adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK].drive == ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL &&
                adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].drive == ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL) {
            LOG_DEBUG("BCM2835 GPIO using fast mode for SWD write");
            bcm2835gpio_bitbang.swd_write = bcm2835gpio_swd_write_fast;
        } else {
            LOG_DEBUG("BCM2835 GPIO using generic mode for SWD write");
            bcm2835gpio_bitbang.swd_write = bcm2835gpio_swd_write_generic;
        }
    }
 
    initialize_gpio(ADAPTER_GPIO_IDX_SRST);
    initialize_gpio(ADAPTER_GPIO_IDX_LED);
 
    return ERROR_OK;
}
 
static int bcm2835gpio_quit(void)
{
    if (transport_is_jtag()) {
        restore_gpio(ADAPTER_GPIO_IDX_TDO);
        restore_gpio(ADAPTER_GPIO_IDX_TDI);
        restore_gpio(ADAPTER_GPIO_IDX_TCK);
        restore_gpio(ADAPTER_GPIO_IDX_TMS);
        restore_gpio(ADAPTER_GPIO_IDX_TRST);
    }
 
    if (transport_is_swd()) {
        /* Restore swdio/swdio_dir to their initial modes, even if that means
         * connecting two outputs. Begin by making swdio an input so that the
         * current and final states of swdio and swdio_dir do not have to be
         * considered to calculate the safe restoration order.
         */
        INP_GPIO(adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num);
        restore_gpio(ADAPTER_GPIO_IDX_SWDIO_DIR);
        restore_gpio(ADAPTER_GPIO_IDX_SWDIO);
        restore_gpio(ADAPTER_GPIO_IDX_SWCLK);
    }
 
    restore_gpio(ADAPTER_GPIO_IDX_SRST);
    restore_gpio(ADAPTER_GPIO_IDX_LED);
 
    if (pads_base != MAP_FAILED) {
        /* Restore drive strength. MSB is password ("5A") */
        pads_base[BCM2835_PADS_GPIO_0_27_OFFSET] = 0x5A000000 | initial_drive_strength_etc;
    }
    bcm2835gpio_munmap();
    free(bcm2835_peri_mem_dev);
 
    return ERROR_OK;
}
 
 
static const char * const bcm2835_transports[] = { "jtag", "swd", NULL };
 
static struct jtag_interface bcm2835gpio_interface = {
    .supported = DEBUG_CAP_TMS_SEQ,
    .execute_queue = bitbang_execute_queue,
};
struct adapter_driver bcm2835gpio_adapter_driver = {
    .name = "bcm2835gpio",
    .transports = bcm2835_transports,
    .commands = bcm2835gpio_command_handlers,
 
    .init = bcm2835gpio_init,
    .quit = bcm2835gpio_quit,
    .reset = bcm2835gpio_reset,
    .speed = bcm2835gpio_speed,
    .khz = bcm2835gpio_khz,
    .speed_div = bcm2835gpio_speed_div,
 
    .jtag_ops = &bcm2835gpio_interface,
    .swd_ops = &bitbang_swd,
};