bitbang.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
/***************************************************************************
 *   Copyright (C) 2005 by Dominic Rath                                    *
 *   Dominic.Rath@gmx.de                                                   *
 *                                                                         *
 *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
 *   oyvind.harboe@zylin.com                                               *
 ***************************************************************************/
 
/* 2014-12: Addition of the SWD protocol support is based on the initial work
 * by Paul Fertser and modifications by Jean-Christian de Rivaz. */
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include "bitbang.h"
#include <jtag/interface.h>
#include <jtag/commands.h>
 
static int bitbang_stableclocks(int num_cycles);
 
static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk);
 
struct bitbang_interface *bitbang_interface;
 
/* DANGER!!!! clock absolutely *MUST* be 0 in idle or reset won't work!
 *
 * Set this to 1 and str912 reset halt will fail.
 *
 * If someone can submit a patch with an explanation it will be greatly
 * appreciated, but as far as I can tell (ØH) DCLK is generated upon
 * clk = 0 in TAP_IDLE. Good luck deducing that from the ARM documentation!
 * The ARM documentation uses the term "DCLK is asserted while in the TAP_IDLE
 * state". With hardware there is no such thing as *while* in a state. There
 * are only edges. So clk => 0 is in fact a very subtle state transition that
 * happens *while* in the TAP_IDLE state. "#&¤"#¤&"#&"#&
 *
 * For "reset halt" the last thing that happens before srst is asserted
 * is that the breakpoint is set up. If DCLK is not wiggled one last
 * time before the reset, then the breakpoint is not set up and
 * "reset halt" will fail to halt.
 *
 */
#define CLOCK_IDLE() 0
 
/* The bitbang driver leaves the TCK 0 when in idle */
static void bitbang_end_state(tap_state_t state)
{
    assert(tap_is_state_stable(state));
    tap_set_end_state(state);
}
 
static int bitbang_state_move(int skip)
{
    int i = 0, tms = 0;
    uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
    int tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
 
    for (i = skip; i < tms_count; i++) {
        tms = (tms_scan >> i) & 1;
        if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
            return ERROR_FAIL;
        if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
            return ERROR_FAIL;
    }
    if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
        return ERROR_FAIL;
 
    tap_set_state(tap_get_end_state());
    return ERROR_OK;
}
 
static int bitbang_execute_tms(struct jtag_command *cmd)
{
    unsigned num_bits = cmd->cmd.tms->num_bits;
    const uint8_t *bits = cmd->cmd.tms->bits;
 
    LOG_DEBUG_IO("TMS: %d bits", num_bits);
 
    int tms = 0;
    for (unsigned i = 0; i < num_bits; i++) {
        tms = ((bits[i/8] >> (i % 8)) & 1);
        if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
            return ERROR_FAIL;
        if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
            return ERROR_FAIL;
    }
    if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
        return ERROR_FAIL;
 
    return ERROR_OK;
}
 
static int bitbang_path_move(struct pathmove_command *cmd)
{
    int num_states = cmd->num_states;
    int state_count;
    int tms = 0;
 
    state_count = 0;
    while (num_states) {
        if (tap_state_transition(tap_get_state(), false) == cmd->path[state_count])
            tms = 0;
        else if (tap_state_transition(tap_get_state(), true) == cmd->path[state_count])
            tms = 1;
        else {
            LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition",
                tap_state_name(tap_get_state()),
                tap_state_name(cmd->path[state_count]));
            exit(-1);
        }
 
        if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
            return ERROR_FAIL;
        if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
            return ERROR_FAIL;
 
        tap_set_state(cmd->path[state_count]);
        state_count++;
        num_states--;
    }
 
    if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
        return ERROR_FAIL;
 
    tap_set_end_state(tap_get_state());
    return ERROR_OK;
}
 
static int bitbang_runtest(int num_cycles)
{
    int i;
 
    tap_state_t saved_end_state = tap_get_end_state();
 
    /* only do a state_move when we're not already in IDLE */
    if (tap_get_state() != TAP_IDLE) {
        bitbang_end_state(TAP_IDLE);
        if (bitbang_state_move(0) != ERROR_OK)
            return ERROR_FAIL;
    }
 
    /* execute num_cycles */
    for (i = 0; i < num_cycles; i++) {
        if (bitbang_interface->write(0, 0, 0) != ERROR_OK)
            return ERROR_FAIL;
        if (bitbang_interface->write(1, 0, 0) != ERROR_OK)
            return ERROR_FAIL;
    }
    if (bitbang_interface->write(CLOCK_IDLE(), 0, 0) != ERROR_OK)
        return ERROR_FAIL;
 
    /* finish in end_state */
    bitbang_end_state(saved_end_state);
    if (tap_get_state() != tap_get_end_state())
        if (bitbang_state_move(0) != ERROR_OK)
            return ERROR_FAIL;
 
    return ERROR_OK;
}
 
static int bitbang_stableclocks(int num_cycles)
{
    int tms = (tap_get_state() == TAP_RESET ? 1 : 0);
    int i;
 
    /* send num_cycles clocks onto the cable */
    for (i = 0; i < num_cycles; i++) {
        if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
            return ERROR_FAIL;
        if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
            return ERROR_FAIL;
    }
 
    return ERROR_OK;
}
 
static int bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer,
        unsigned scan_size)
{
    tap_state_t saved_end_state = tap_get_end_state();
    unsigned bit_cnt;
 
    if (!((!ir_scan &&
            (tap_get_state() == TAP_DRSHIFT)) ||
            (ir_scan && (tap_get_state() == TAP_IRSHIFT)))) {
        if (ir_scan)
            bitbang_end_state(TAP_IRSHIFT);
        else
            bitbang_end_state(TAP_DRSHIFT);
 
        if (bitbang_state_move(0) != ERROR_OK)
            return ERROR_FAIL;
        bitbang_end_state(saved_end_state);
    }
 
    size_t buffered = 0;
    for (bit_cnt = 0; bit_cnt < scan_size; bit_cnt++) {
        int tms = (bit_cnt == scan_size-1) ? 1 : 0;
        int tdi;
        int bytec = bit_cnt/8;
        int bcval = 1 << (bit_cnt % 8);
 
        /* if we're just reading the scan, but don't care about the output
         * default to outputting 'low', this also makes valgrind traces more readable,
         * as it removes the dependency on an uninitialised value
         */
        tdi = 0;
        if ((type != SCAN_IN) && (buffer[bytec] & bcval))
            tdi = 1;
 
        if (bitbang_interface->write(0, tms, tdi) != ERROR_OK)
            return ERROR_FAIL;
 
        if (type != SCAN_OUT) {
            if (bitbang_interface->buf_size) {
                if (bitbang_interface->sample() != ERROR_OK)
                    return ERROR_FAIL;
                buffered++;
            } else {
                switch (bitbang_interface->read()) {
                    case BB_LOW:
                        buffer[bytec] &= ~bcval;
                        break;
                    case BB_HIGH:
                        buffer[bytec] |= bcval;
                        break;
                    default:
                        return ERROR_FAIL;
                }
            }
        }
 
        if (bitbang_interface->write(1, tms, tdi) != ERROR_OK)
            return ERROR_FAIL;
 
        if (type != SCAN_OUT && bitbang_interface->buf_size &&
                (buffered == bitbang_interface->buf_size ||
                 bit_cnt == scan_size - 1)) {
            for (unsigned i = bit_cnt + 1 - buffered; i <= bit_cnt; i++) {
                switch (bitbang_interface->read_sample()) {
                    case BB_LOW:
                        buffer[i/8] &= ~(1 << (i % 8));
                        break;
                    case BB_HIGH:
                        buffer[i/8] |= 1 << (i % 8);
                        break;
                    default:
                        return ERROR_FAIL;
                }
            }
            buffered = 0;
        }
    }
 
    if (tap_get_state() != tap_get_end_state()) {
        /* we *KNOW* the above loop transitioned out of
         * the shift state, so we skip the first state
         * and move directly to the end state.
         */
        if (bitbang_state_move(1) != ERROR_OK)
            return ERROR_FAIL;
    }
    return ERROR_OK;
}
 
int bitbang_execute_queue(void)
{
    struct jtag_command *cmd = jtag_command_queue;  /* currently processed command */
    int scan_size;
    enum scan_type type;
    uint8_t *buffer;
    int retval;
 
    if (!bitbang_interface) {
        LOG_ERROR("BUG: Bitbang interface called, but not yet initialized");
        exit(-1);
    }
 
    /* return ERROR_OK, unless a jtag_read_buffer returns a failed check
     * that wasn't handled by a caller-provided error handler
     */
    retval = ERROR_OK;
 
    if (bitbang_interface->blink) {
        if (bitbang_interface->blink(1) != ERROR_OK)
            return ERROR_FAIL;
    }
 
    while (cmd) {
        switch (cmd->type) {
            case JTAG_RUNTEST:
                LOG_DEBUG_IO("runtest %i cycles, end in %s",
                        cmd->cmd.runtest->num_cycles,
                        tap_state_name(cmd->cmd.runtest->end_state));
                bitbang_end_state(cmd->cmd.runtest->end_state);
                if (bitbang_runtest(cmd->cmd.runtest->num_cycles) != ERROR_OK)
                    return ERROR_FAIL;
                break;
 
            case JTAG_STABLECLOCKS:
                /* this is only allowed while in a stable state.  A check for a stable
                 * state was done in jtag_add_clocks()
                 */
                if (bitbang_stableclocks(cmd->cmd.stableclocks->num_cycles) != ERROR_OK)
                    return ERROR_FAIL;
                break;
 
            case JTAG_TLR_RESET:
                LOG_DEBUG_IO("statemove end in %s",
                        tap_state_name(cmd->cmd.statemove->end_state));
                bitbang_end_state(cmd->cmd.statemove->end_state);
                if (bitbang_state_move(0) != ERROR_OK)
                    return ERROR_FAIL;
                break;
            case JTAG_PATHMOVE:
                LOG_DEBUG_IO("pathmove: %i states, end in %s",
                        cmd->cmd.pathmove->num_states,
                        tap_state_name(cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]));
                if (bitbang_path_move(cmd->cmd.pathmove) != ERROR_OK)
                    return ERROR_FAIL;
                break;
            case JTAG_SCAN:
                bitbang_end_state(cmd->cmd.scan->end_state);
                scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
                LOG_DEBUG_IO("%s scan %d bits; end in %s",
                        (cmd->cmd.scan->ir_scan) ? "IR" : "DR",
                        scan_size,
                    tap_state_name(cmd->cmd.scan->end_state));
                type = jtag_scan_type(cmd->cmd.scan);
                if (bitbang_scan(cmd->cmd.scan->ir_scan, type, buffer,
                            scan_size) != ERROR_OK)
                    return ERROR_FAIL;
                if (jtag_read_buffer(buffer, cmd->cmd.scan) != ERROR_OK)
                    retval = ERROR_JTAG_QUEUE_FAILED;
                free(buffer);
                break;
            case JTAG_SLEEP:
                LOG_DEBUG_IO("sleep %" PRIu32, cmd->cmd.sleep->us);
                jtag_sleep(cmd->cmd.sleep->us);
                break;
            case JTAG_TMS:
                retval = bitbang_execute_tms(cmd);
                break;
            default:
                LOG_ERROR("BUG: unknown JTAG command type encountered");
                exit(-1);
        }
        cmd = cmd->next;
    }
    if (bitbang_interface->blink) {
        if (bitbang_interface->blink(0) != ERROR_OK)
            return ERROR_FAIL;
    }
 
    return retval;
}
 
static int queued_retval;
 
static int bitbang_swd_init(void)
{
    LOG_DEBUG("bitbang_swd_init");
    return ERROR_OK;
}
 
static void bitbang_swd_exchange(bool rnw, uint8_t buf[], unsigned int offset, unsigned int bit_cnt)
{
    if (bitbang_interface->blink) {
        /* FIXME: we should manage errors */
        bitbang_interface->blink(1);
    }
 
    for (unsigned int i = offset; i < bit_cnt + offset; i++) {
        int bytec = i/8;
        int bcval = 1 << (i % 8);
        int swdio = !rnw && (buf[bytec] & bcval);
 
        bitbang_interface->swd_write(0, swdio);
 
        if (rnw && buf) {
            if (bitbang_interface->swdio_read())
                buf[bytec] |= bcval;
            else
                buf[bytec] &= ~bcval;
        }
 
        bitbang_interface->swd_write(1, swdio);
    }
 
    if (bitbang_interface->blink) {
        /* FIXME: we should manage errors */
        bitbang_interface->blink(0);
    }
}
 
static int bitbang_swd_switch_seq(enum swd_special_seq seq)
{
    switch (seq) {
    case LINE_RESET:
        LOG_DEBUG_IO("SWD line reset");
        bitbang_swd_exchange(false, (uint8_t *)swd_seq_line_reset, 0, swd_seq_line_reset_len);
        break;
    case JTAG_TO_SWD:
        LOG_DEBUG("JTAG-to-SWD");
        bitbang_swd_exchange(false, (uint8_t *)swd_seq_jtag_to_swd, 0, swd_seq_jtag_to_swd_len);
        break;
    case JTAG_TO_DORMANT:
        LOG_DEBUG("JTAG-to-DORMANT");
        bitbang_swd_exchange(false, (uint8_t *)swd_seq_jtag_to_dormant, 0, swd_seq_jtag_to_dormant_len);
        break;
    case SWD_TO_JTAG:
        LOG_DEBUG("SWD-to-JTAG");
        bitbang_swd_exchange(false, (uint8_t *)swd_seq_swd_to_jtag, 0, swd_seq_swd_to_jtag_len);
        break;
    case SWD_TO_DORMANT:
        LOG_DEBUG("SWD-to-DORMANT");
        bitbang_swd_exchange(false, (uint8_t *)swd_seq_swd_to_dormant, 0, swd_seq_swd_to_dormant_len);
        break;
    case DORMANT_TO_SWD:
        LOG_DEBUG("DORMANT-to-SWD");
        bitbang_swd_exchange(false, (uint8_t *)swd_seq_dormant_to_swd, 0, swd_seq_dormant_to_swd_len);
        break;
    case DORMANT_TO_JTAG:
        LOG_DEBUG("DORMANT-to-JTAG");
        bitbang_swd_exchange(false, (uint8_t *)swd_seq_dormant_to_jtag, 0, swd_seq_dormant_to_jtag_len);
        break;
    default:
        LOG_ERROR("Sequence %d not supported", seq);
        return ERROR_FAIL;
    }
 
    return ERROR_OK;
}
 
static void swd_clear_sticky_errors(void)
{
    bitbang_swd_write_reg(swd_cmd(false,  false, DP_ABORT),
        STKCMPCLR | STKERRCLR | WDERRCLR | ORUNERRCLR, 0);
}
 
static void bitbang_swd_read_reg(uint8_t cmd, uint32_t *value, uint32_t ap_delay_clk)
{
    assert(cmd & SWD_CMD_RNW);
 
    if (queued_retval != ERROR_OK) {
        LOG_DEBUG("Skip bitbang_swd_read_reg because queued_retval=%d", queued_retval);
        return;
    }
 
    for (;;) {
        uint8_t trn_ack_data_parity_trn[DIV_ROUND_UP(4 + 3 + 32 + 1 + 4, 8)];
 
        cmd |= SWD_CMD_START | SWD_CMD_PARK;
        bitbang_swd_exchange(false, &cmd, 0, 8);
 
        bitbang_interface->swdio_drive(false);
        bitbang_swd_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3 + 32 + 1 + 1);
        bitbang_interface->swdio_drive(true);
 
        int ack = buf_get_u32(trn_ack_data_parity_trn, 1, 3);
        uint32_t data = buf_get_u32(trn_ack_data_parity_trn, 1 + 3, 32);
        int parity = buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 32, 1);
 
        LOG_DEBUG_IO("%s %s read reg %X = %08" PRIx32,
              ack == SWD_ACK_OK ? "OK" : ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
              cmd & SWD_CMD_APNDP ? "AP" : "DP",
              (cmd & SWD_CMD_A32) >> 1,
              data);
 
        if (ack == SWD_ACK_WAIT) {
            swd_clear_sticky_errors();
            continue;
        } else if (ack != SWD_ACK_OK) {
            queued_retval = swd_ack_to_error_code(ack);
            return;
        }
 
        if (parity != parity_u32(data)) {
            LOG_ERROR("Wrong parity detected");
            queued_retval = ERROR_FAIL;
            return;
        }
        if (value)
            *value = data;
        if (cmd & SWD_CMD_APNDP)
            bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
        return;
    }
}
 
static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk)
{
    assert(!(cmd & SWD_CMD_RNW));
 
    if (queued_retval != ERROR_OK) {
        LOG_DEBUG("Skip bitbang_swd_write_reg because queued_retval=%d", queued_retval);
        return;
    }
 
    /* Devices do not reply to DP_TARGETSEL write cmd, ignore received ack */
    bool check_ack = swd_cmd_returns_ack(cmd);
 
    /* init the array to silence scan-build */
    uint8_t trn_ack_data_parity_trn[DIV_ROUND_UP(4 + 3 + 32 + 1 + 4, 8)] = {0};
    for (;;) {
        buf_set_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32, value);
        buf_set_u32(trn_ack_data_parity_trn, 1 + 3 + 1 + 32, 1, parity_u32(value));
 
        cmd |= SWD_CMD_START | SWD_CMD_PARK;
        bitbang_swd_exchange(false, &cmd, 0, 8);
 
        bitbang_interface->swdio_drive(false);
        bitbang_swd_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3 + 1);
        bitbang_interface->swdio_drive(true);
        bitbang_swd_exchange(false, trn_ack_data_parity_trn, 1 + 3 + 1, 32 + 1);
 
        int ack = buf_get_u32(trn_ack_data_parity_trn, 1, 3);
 
        LOG_DEBUG_IO("%s%s %s write 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",
              (cmd & SWD_CMD_A32) >> 1,
              buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32));
 
        if (check_ack) {
            if (ack == SWD_ACK_WAIT) {
                swd_clear_sticky_errors();
                continue;
            } else if (ack != SWD_ACK_OK) {
                queued_retval = swd_ack_to_error_code(ack);
                return;
            }
        }
 
        if (cmd & SWD_CMD_APNDP)
            bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
        return;
    }
}
 
static int bitbang_swd_run_queue(void)
{
    /* A transaction must be followed by another transaction or at least 8 idle cycles to
     * ensure that data is clocked through the AP. */
    bitbang_swd_exchange(true, NULL, 0, 8);
 
    int retval = queued_retval;
    queued_retval = ERROR_OK;
    LOG_DEBUG_IO("SWD queue return value: %02x", retval);
    return retval;
}
 
const struct swd_driver bitbang_swd = {
    .init = bitbang_swd_init,
    .switch_seq = bitbang_swd_switch_seq,
    .read_reg = bitbang_swd_read_reg,
    .write_reg = bitbang_swd_write_reg,
    .run = bitbang_swd_run_queue,
};