linuxspidev.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
/* Copyright (C) 2020 by Lup Yuen Lee <luppy@appkaki.com>
 * Copyright (C) 2024 by Richard Pasek <rpasek@google.com>
 */
 
/* Uncomment to log SPI exchanges (very verbose, slows things down a lot)
 *
 * A quick note on interpreting SPI exchange messages:
 *
 * This implementation works by performing SPI exchanges with MOSI and MISO
 * tied together with a 1K resistor. This combined signal becomes SWDIO.
 *
 * Since we are performing SPI exchanges, (reading and writing at the same
 * time) this means when the target isn't driving SWDIO, what is written by
 * the host should also be read by the host.
 *
 * On SWD writes:
 *   The TX and RX data should match except for the ACK bits from the target
 *     swd write reg exchange: len=6
 *      tx_buf=C5 02 40 00 02 2C
 *      rx_buf=C5 42 40 00 02 2C
 *                ^
 *                |
 *          ACK from target
 *
 * On SWD reads:
 *   Only the command byte should match
 *     swd read reg exchange: len=6
 *      tx_buf=B1 00 00 00 00 00
 *      rx_buf=B1 40 20 00 00 F8
 *             ^^
 *             ||
 *     Command packet from host
 *
 */
// #define LOG_SPI_EXCHANGE
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include <stdint.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/spi/spidev.h>
#include <jtag/adapter.h>
#include <jtag/swd.h>
#include <jtag/interface.h>
#include <jtag/commands.h>
 
// Number of bits per SPI exchange
#define SPI_BITS 8
 
// Time in uS after the last bit of transfer before deselecting the device
#define SPI_DESELECT_DELAY 0
 
// Maximum number of SWD transactions to queue together in a SPI exchange
#define MAX_QUEUE_ENTRIES 64
 
#define CMD_BITS 8
#define TURN_BITS 1
#define ACK_BITS 3
#define DATA_BITS 32
#define PARITY_BITS 1
 
#define SWD_WR_BITS (CMD_BITS + TURN_BITS + ACK_BITS + TURN_BITS + DATA_BITS + PARITY_BITS)
#define SWD_RD_BITS (CMD_BITS + TURN_BITS + ACK_BITS + DATA_BITS + PARITY_BITS + TURN_BITS)
#define SWD_OP_BITS (MAX(SWD_WR_BITS, SWD_RD_BITS))
#define SWD_OP_BYTES (DIV_ROUND_UP(SWD_OP_BITS, SPI_BITS))
 
#define AP_DELAY_CLOCKS 8
#define AP_DELAY_BYTES (DIV_ROUND_UP(AP_DELAY_CLOCKS, SPI_BITS))
 
#define END_IDLE_CLOCKS 8
#define END_IDLE_BYTES (DIV_ROUND_UP(END_IDLE_CLOCKS, SPI_BITS))
 
// File descriptor for SPI device
static int spi_fd = -1;
 
// SPI Configuration
static char *spi_path;
static uint32_t spi_mode = SPI_MODE_3; // Note: SPI in LSB mode is not often supported. We'll flip LSB to MSB ourselves.
static uint32_t spi_speed;
 
struct queue_info {
    unsigned int buf_idx;
    uint32_t *rx_ptr;
};
 
static int queue_retval;
static unsigned int max_queue_entries;
static unsigned int queue_fill;
static unsigned int queue_buf_fill;
static unsigned int queue_buf_size;
static struct queue_info *queue_infos;
static uint8_t *queue_tx_buf;
static uint8_t *queue_rx_buf;
static uint8_t *tx_flip_buf;
 
static int spidev_swd_switch_seq(enum swd_special_seq seq);
static void spidev_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk);
 
static void spi_exchange(const uint8_t *tx_data, uint8_t *rx_data, unsigned int len)
{
#ifdef LOG_SPI_EXCHANGE
    LOG_OUTPUT("exchange: len=%u\n", len);
#endif // LOG_SPI_EXCHANGE
 
    if (len == 0) {
        LOG_DEBUG("exchange with no length");
        return;
    }
 
    if (!tx_data && !rx_data) {
        LOG_DEBUG("exchange with no valid tx or rx pointers");
        return;
    }
 
    if (len > queue_buf_size) {
        LOG_ERROR("exchange too large len=%u ", len);
        return;
    }
 
    if (tx_data) {
        // Reverse LSB to MSB
        for (unsigned int i = 0; i < len; i++)
            tx_flip_buf[i] = flip_u32(tx_data[i], 8);
 
#ifdef LOG_SPI_EXCHANGE
        if (len != 0) {
            LOG_OUTPUT(" tx_buf=");
            for (unsigned int i = 0; i < len; i++)
                LOG_OUTPUT("%.2" PRIx8 " ", tx_flip_buf[i]);
        }
        LOG_OUTPUT("\n");
#endif // LOG_SPI_EXCHANGE
    }
    // Transmit the MSB buffer to SPI device.
    struct spi_ioc_transfer tr = {
        /* The following must be cast to unsigned long to compile correctly on
         * 32 and 64 bit machines (as is done in the spidev examples in Linux
         * kernel code in tools/spi/).
         */
        .tx_buf = (unsigned long)(tx_data ? tx_flip_buf : NULL),
        .rx_buf = (unsigned long)rx_data,
        .len = len,
        .delay_usecs = SPI_DESELECT_DELAY,
        .speed_hz = spi_speed,
        .bits_per_word = SPI_BITS,
    };
    int ret = ioctl(spi_fd, SPI_IOC_MESSAGE(1), &tr);
 
    if (ret < 1) {
        LOG_ERROR("exchange failed");
        return;
    }
 
    if (rx_data) {
#ifdef LOG_SPI_EXCHANGE
        if (len != 0) {
            LOG_OUTPUT(" rx_buf=");
            for (unsigned int i = 0; i < len; i++)
                LOG_OUTPUT("%.2" PRIx8 " ", rx_data[i]);
        }
        LOG_OUTPUT("\n");
#endif // LOG_SPI_EXCHANGE
 
        // Reverse MSB to LSB
        for (unsigned int i = 0; i < len; i++)
            rx_data[i] = flip_u32(rx_data[i], 8);
    }
}
 
static int spidev_speed(int speed)
{
    uint32_t tmp_speed = speed;
 
    int ret = ioctl(spi_fd, SPI_IOC_WR_MAX_SPEED_HZ, &tmp_speed);
    if (ret == -1) {
        LOG_ERROR("Failed to set SPI %d speed", speed);
        return ERROR_FAIL;
    }
 
    spi_speed = speed;
 
    return ERROR_OK;
}
 
static int spidev_speed_div(int speed, int *khz)
{
    *khz = speed / 1000;
    return ERROR_OK;
}
 
static int spidev_khz(int khz, int *jtag_speed)
{
    if (khz == 0) {
        LOG_DEBUG("RCLK not supported");
        return ERROR_FAIL;
    }
 
    *jtag_speed = khz * 1000;
    return ERROR_OK;
}
 
static void spidev_free_queue(void)
{
    max_queue_entries = 0;
    queue_buf_size = 0;
 
    free(queue_infos);
    queue_infos = NULL;
 
    free(queue_tx_buf);
    queue_tx_buf = NULL;
 
    free(queue_rx_buf);
    queue_rx_buf = NULL;
 
    free(tx_flip_buf);
    tx_flip_buf = NULL;
}
 
static void spidev_clear_queue(void)
{
    queue_fill = 0;
    queue_buf_fill = 0;
 
    memset(queue_infos, 0, sizeof(struct queue_info) * max_queue_entries);
    memset(queue_tx_buf, 0, queue_buf_size);
    memset(queue_rx_buf, 0, queue_buf_size);
    memset(tx_flip_buf, 0, queue_buf_size);
}
 
static int spidev_alloc_queue(unsigned int new_queue_entries)
{
    if (queue_fill || queue_buf_fill) {
        LOG_ERROR("Can't realloc queue when queue is in use");
        return ERROR_FAIL;
    }
 
    unsigned int new_queue_buf_size =
        (new_queue_entries * (SWD_OP_BYTES + AP_DELAY_BYTES)) + END_IDLE_BYTES;
 
    queue_infos = realloc(queue_infos, sizeof(struct queue_info) * new_queue_entries);
    if (!queue_infos)
        goto realloc_fail;
 
    queue_tx_buf = realloc(queue_tx_buf, new_queue_buf_size);
    if (!queue_tx_buf)
        goto realloc_fail;
 
    queue_rx_buf = realloc(queue_rx_buf, new_queue_buf_size);
    if (!queue_rx_buf)
        goto realloc_fail;
 
    tx_flip_buf = realloc(tx_flip_buf, new_queue_buf_size);
    if (!tx_flip_buf)
        goto realloc_fail;
 
    max_queue_entries = new_queue_entries;
    queue_buf_size = new_queue_buf_size;
 
    spidev_clear_queue();
 
    LOG_DEBUG("Set queue entries to %u (buffers %u bytes)", max_queue_entries, queue_buf_size);
 
    return ERROR_OK;
 
realloc_fail:
    spidev_free_queue();
 
    LOG_ERROR("Couldn't allocate queue. Out of memory.");
    return ERROR_FAIL;
}
 
static int spidev_init(void)
{
    LOG_INFO("SPI SWD driver");
 
    if (spi_fd >= 0)
        return ERROR_OK;
 
    if (!spi_path) {
        LOG_ERROR("Path to spidev not set");
        return ERROR_JTAG_INIT_FAILED;
    }
 
    // Open SPI device.
    spi_fd = open(spi_path, O_RDWR);
    if (spi_fd < 0) {
        LOG_ERROR("Failed to open SPI port at %s", spi_path);
        return ERROR_JTAG_INIT_FAILED;
    }
 
    // Set SPI mode.
    int ret = ioctl(spi_fd, SPI_IOC_WR_MODE32, &spi_mode);
    if (ret == -1) {
        LOG_ERROR("Failed to set SPI mode 0x%" PRIx32, spi_mode);
        return ERROR_JTAG_INIT_FAILED;
    }
 
    // Set SPI bits per word.
    uint32_t spi_bits = SPI_BITS;
    ret = ioctl(spi_fd, SPI_IOC_WR_BITS_PER_WORD, &spi_bits);
    if (ret == -1) {
        LOG_ERROR("Failed to set SPI %" PRIu8 " bits per transfer", spi_bits);
        return ERROR_JTAG_INIT_FAILED;
    }
 
    LOG_INFO("Opened SPI device at %s in mode 0x%" PRIx32 " with %" PRIu8 " bits ",
        spi_path, spi_mode, spi_bits);
 
    if (max_queue_entries == 0) {
        ret = spidev_alloc_queue(MAX_QUEUE_ENTRIES);
        if (ret != ERROR_OK)
            return ERROR_JTAG_INIT_FAILED;
    }
 
    return ERROR_OK;
}
 
static int spidev_quit(void)
{
    spidev_free_queue();
 
    if (spi_fd < 0)
        return ERROR_OK;
 
    close(spi_fd);
    spi_fd = -1;
 
    free(spi_path);
    spi_path = NULL;
 
    return ERROR_OK;
}
 
static int spidev_swd_init(void)
{
    LOG_DEBUG("spidev_swd_init");
    return ERROR_OK;
}
 
static int spidev_swd_execute_queue(unsigned int end_idle_bytes)
{
    LOG_DEBUG_IO("Executing %u queued transactions", queue_fill);
 
    if (queue_retval != ERROR_OK) {
        LOG_DEBUG_IO("Skipping due to previous errors: %d", queue_retval);
        goto skip;
    }
 
    /* A transaction must be followed by another transaction or at least 8 idle
     * cycles to ensure that data is clocked through the AP. Since the tx
     * buffer is zeroed after each queue run, every byte added to the buffer
     * fill will add on an additional 8 idle cycles.
     */
    queue_buf_fill += end_idle_bytes;
 
    spi_exchange(queue_tx_buf, queue_rx_buf, queue_buf_fill);
 
    for (unsigned int queue_idx = 0; queue_idx < queue_fill; queue_idx++) {
        unsigned int buf_idx = queue_infos[queue_idx].buf_idx;
        uint8_t *tx_ptr = &queue_tx_buf[buf_idx];
        uint8_t *rx_ptr = &queue_rx_buf[buf_idx];
        uint8_t cmd = buf_get_u32(tx_ptr, 0, CMD_BITS);
        bool read = cmd & SWD_CMD_RNW ? true : false;
        int ack = buf_get_u32(rx_ptr, CMD_BITS + TURN_BITS, ACK_BITS);
        uint32_t data = read ?
            buf_get_u32(rx_ptr, CMD_BITS + TURN_BITS + ACK_BITS, DATA_BITS) :
            buf_get_u32(tx_ptr, CMD_BITS + TURN_BITS + ACK_BITS + TURN_BITS, DATA_BITS);
 
        // Devices do not reply to DP_TARGETSEL write cmd, ignore received ack
        bool check_ack = swd_cmd_returns_ack(cmd);
 
        LOG_CUSTOM_LEVEL((check_ack && ack != SWD_ACK_OK) ? LOG_LVL_DEBUG : LOG_LVL_DEBUG_IO,
                "%s%s %s %s reg %X = %08" PRIx32,
                check_ack ? "" : "ack ignored ",
                ack == SWD_ACK_OK ? "OK" :
                ack == SWD_ACK_WAIT ? "WAIT" :
                ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
                cmd & SWD_CMD_APNDP ? "AP" : "DP",
                read ? "read" : "write",
                (cmd & SWD_CMD_A32) >> 1,
                data);
 
        if (ack != SWD_ACK_OK && check_ack) {
            queue_retval = swd_ack_to_error_code(ack);
            goto skip;
 
        } else if (read) {
            int parity = buf_get_u32(rx_ptr, CMD_BITS + TURN_BITS + ACK_BITS + DATA_BITS, PARITY_BITS);
 
            if (parity != parity_u32(data)) {
                LOG_ERROR("SWD Read data parity mismatch");
                queue_retval = ERROR_FAIL;
                goto skip;
            }
 
            if (queue_infos[queue_idx].rx_ptr)
                *queue_infos[queue_idx].rx_ptr = data;
        }
    }
 
skip:
    spidev_clear_queue();
 
    int retval = queue_retval;
    queue_retval = ERROR_OK;
 
    return retval;
}
 
static int spidev_swd_run_queue(void)
{
    /* Since we are unsure if another SWD transaction will follow the
     * transactions we are just about to execute, we need to add on 8 idle
     * cycles.
     */
    return spidev_swd_execute_queue(END_IDLE_BYTES);
}
 
static void spidev_swd_queue_cmd(uint8_t cmd, uint32_t *dst, uint32_t data, uint32_t ap_delay_clk)
{
    unsigned int swd_op_bytes = DIV_ROUND_UP(SWD_OP_BITS + ap_delay_clk, SPI_BITS);
 
    if (queue_fill >= max_queue_entries ||
        queue_buf_fill + swd_op_bytes + END_IDLE_BYTES > queue_buf_size) {
        /* Not enough room in the queue. Run the queue. No idle bytes are
         * needed because we are going to execute transactions right after
         * the queue is emptied.
         */
        queue_retval = spidev_swd_execute_queue(0);
    }
 
    if (queue_retval != ERROR_OK)
        return;
 
    uint8_t *tx_ptr = &queue_tx_buf[queue_buf_fill];
 
    cmd |= SWD_CMD_START | SWD_CMD_PARK;
 
    buf_set_u32(tx_ptr, 0, CMD_BITS, cmd);
 
    if (cmd & SWD_CMD_RNW) {
        // Queue a read transaction
        queue_infos[queue_fill].rx_ptr = dst;
    } else {
        // Queue a write transaction
        buf_set_u32(tx_ptr,
            CMD_BITS + TURN_BITS + ACK_BITS + TURN_BITS, DATA_BITS, data);
        buf_set_u32(tx_ptr,
            CMD_BITS + TURN_BITS + ACK_BITS + TURN_BITS + DATA_BITS, PARITY_BITS, parity_u32(data));
    }
 
    queue_infos[queue_fill].buf_idx = queue_buf_fill;
 
    /* Add idle cycles after AP accesses to avoid WAIT. Buffer is already
     * zeroed so we just need to advance the pointer to add idle cycles.
     */
    queue_buf_fill += swd_op_bytes;
 
    queue_fill++;
}
 
static void spidev_swd_read_reg(uint8_t cmd, uint32_t *value, uint32_t ap_delay_clk)
{
    assert(cmd & SWD_CMD_RNW);
    spidev_swd_queue_cmd(cmd, value, 0, ap_delay_clk);
}
 
static void spidev_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk)
{
    assert(!(cmd & SWD_CMD_RNW));
    spidev_swd_queue_cmd(cmd, NULL, value, ap_delay_clk);
}
 
static int spidev_swd_switch_seq(enum swd_special_seq seq)
{
    switch (seq) {
    case LINE_RESET:
        LOG_DEBUG_IO("SWD line reset");
        spi_exchange(swd_seq_line_reset, NULL, swd_seq_line_reset_len / SPI_BITS);
        break;
    case JTAG_TO_SWD:
        LOG_DEBUG("JTAG-to-SWD");
        spi_exchange(swd_seq_jtag_to_swd, NULL, swd_seq_jtag_to_swd_len / SPI_BITS);
        break;
    case JTAG_TO_DORMANT:
        LOG_DEBUG("JTAG-to-DORMANT");
        spi_exchange(swd_seq_jtag_to_dormant, NULL, swd_seq_jtag_to_dormant_len / SPI_BITS);
        break;
    case SWD_TO_JTAG:
        LOG_DEBUG("SWD-to-JTAG");
        spi_exchange(swd_seq_swd_to_jtag, NULL, swd_seq_swd_to_jtag_len / SPI_BITS);
        break;
    case SWD_TO_DORMANT:
        LOG_DEBUG("SWD-to-DORMANT");
        spi_exchange(swd_seq_swd_to_dormant, NULL, swd_seq_swd_to_dormant_len / SPI_BITS);
        break;
    case DORMANT_TO_SWD:
        LOG_DEBUG("DORMANT-to-SWD");
        spi_exchange(swd_seq_dormant_to_swd, NULL, swd_seq_dormant_to_swd_len / SPI_BITS);
        break;
    case DORMANT_TO_JTAG:
        LOG_DEBUG("DORMANT-to-JTAG");
        spi_exchange(swd_seq_dormant_to_jtag, NULL, swd_seq_dormant_to_jtag_len / SPI_BITS);
        break;
    default:
        LOG_ERROR("Sequence %d not supported", seq);
        return ERROR_FAIL;
    }
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(spidev_handle_path_command)
{
    if (CMD_ARGC != 1)
        return ERROR_COMMAND_SYNTAX_ERROR;
 
    free(spi_path);
    spi_path = strdup(CMD_ARGV[0]);
    if (!spi_path) {
        LOG_ERROR("Out of memory");
        return ERROR_FAIL;
    }
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(spidev_handle_mode_command)
{
    if (CMD_ARGC != 1)
        return ERROR_COMMAND_SYNTAX_ERROR;
 
    COMMAND_PARSE_NUMBER(u32, CMD_ARGV[0], spi_mode);
    return ERROR_OK;
}
 
COMMAND_HANDLER(spidev_handle_queue_entries_command)
{
    uint32_t new_queue_entries;
 
    if (CMD_ARGC != 1)
        return ERROR_COMMAND_SYNTAX_ERROR;
 
    COMMAND_PARSE_NUMBER(u32, CMD_ARGV[0], new_queue_entries);
 
    return spidev_alloc_queue(new_queue_entries);
}
 
const struct swd_driver spidev_swd = {
    .init = spidev_swd_init,
    .switch_seq = spidev_swd_switch_seq,
    .read_reg = spidev_swd_read_reg,
    .write_reg = spidev_swd_write_reg,
    .run = spidev_swd_run_queue,
};
 
static const struct command_registration spidev_subcommand_handlers[] = {
    {
        .name = "path",
        .handler = &spidev_handle_path_command,
        .mode = COMMAND_CONFIG,
        .help = "set the path to the spidev device",
        .usage = "path_to_spidev",
    },
    {
        .name = "mode",
        .handler = &spidev_handle_mode_command,
        .mode = COMMAND_CONFIG,
        .help = "set the mode of the spi port with optional bit flags (default=3)",
        .usage = "mode",
    },
    {
        .name = "queue_entries",
        .handler = &spidev_handle_queue_entries_command,
        .mode = COMMAND_CONFIG,
        .help = "set the queue entry size (default=64)",
        .usage = "queue_entries",
    },
    COMMAND_REGISTRATION_DONE
};
 
static const struct command_registration spidev_command_handlers[] = {
    {
        .name = "spidev",
        .mode = COMMAND_ANY,
        .help = "perform spidev management",
        .chain = spidev_subcommand_handlers,
        .usage = "",
    },
    COMMAND_REGISTRATION_DONE
};
 
// Only SWD transport supported
static const char *const spidev_transports[] = { "swd", NULL };
 
struct adapter_driver linuxspidev_adapter_driver = {
    .name = "linuxspidev",
    .transports = spidev_transports,
    .commands = spidev_command_handlers,
 
    .init = spidev_init,
    .quit = spidev_quit,
    .speed = spidev_speed,
    .khz = spidev_khz,
    .speed_div = spidev_speed_div,
 
    .swd_ops = &spidev_swd,
};