cmp.c

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/*
 * Connection Management Procedures (IEC 61883-1) helper functions
 *
 * Copyright (c) Clemens Ladisch <[email protected]>
 * Licensed under the terms of the GNU General Public License, version 2.
 */

#include <linux/device.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/module.h>
#include <linux/sched.h>
#include "lib.h"
#include "iso-resources.h"
#include "cmp.h"

#define IMPR_SPEED_MASK     0xc0000000
#define IMPR_SPEED_SHIFT    30
#define IMPR_XSPEED_MASK    0x00000060
#define IMPR_XSPEED_SHIFT   5
#define IMPR_PLUGS_MASK     0x0000001f

#define IPCR_ONLINE     0x80000000
#define IPCR_BCAST_CONN     0x40000000
#define IPCR_P2P_CONN_MASK  0x3f000000
#define IPCR_P2P_CONN_SHIFT 24
#define IPCR_CHANNEL_MASK   0x003f0000
#define IPCR_CHANNEL_SHIFT  16

enum bus_reset_handling {
    ABORT_ON_BUS_RESET,
    SUCCEED_ON_BUS_RESET,
};

static __printf(2, 3)
void cmp_error(struct cmp_connection *c, const char *fmt, ...)
{
    va_list va;

    va_start(va, fmt);
    dev_err(&c->resources.unit->device, "%cPCR%u: %pV",
        'i', c->pcr_index, &(struct va_format){ fmt, &va });
    va_end(va);
}

static int pcr_modify(struct cmp_connection *c,
              __be32 (*modify)(struct cmp_connection *c, __be32 old),
              int (*check)(struct cmp_connection *c, __be32 pcr),
              enum bus_reset_handling bus_reset_handling)
{
    struct fw_device *device = fw_parent_device(c->resources.unit);
    int generation = c->resources.generation;
    int rcode, errors = 0;
    __be32 old_arg, buffer[2];
    int err;

    buffer[0] = c->last_pcr_value;
    for (;;) {
        old_arg = buffer[0];
        buffer[1] = modify(c, buffer[0]);

        rcode = fw_run_transaction(
                device->card, TCODE_LOCK_COMPARE_SWAP,
                device->node_id, generation, device->max_speed,
                CSR_REGISTER_BASE + CSR_IPCR(c->pcr_index),
                buffer, 8);

        if (rcode == RCODE_COMPLETE) {
            if (buffer[0] == old_arg) /* success? */
                break;

            if (check) {
                err = check(c, buffer[0]);
                if (err < 0)
                    return err;
            }
        } else if (rcode == RCODE_GENERATION)
            goto bus_reset;
        else if (rcode_is_permanent_error(rcode) || ++errors >= 3)
            goto io_error;
    }
    c->last_pcr_value = buffer[1];

    return 0;

io_error:
    cmp_error(c, "transaction failed: %s\n", fw_rcode_string(rcode));
    return -EIO;

bus_reset:
    return bus_reset_handling == ABORT_ON_BUS_RESET ? -EAGAIN : 0;
}


int cmp_connection_init(struct cmp_connection *c,
            struct fw_unit *unit,
            unsigned int ipcr_index)
{
    __be32 impr_be;
    u32 impr;
    int err;

    err = snd_fw_transaction(unit, TCODE_READ_QUADLET_REQUEST,
                 CSR_REGISTER_BASE + CSR_IMPR,
                 &impr_be, 4);
    if (err < 0)
        return err;
    impr = be32_to_cpu(impr_be);

    if (ipcr_index >= (impr & IMPR_PLUGS_MASK))
        return -EINVAL;

    err = fw_iso_resources_init(&c->resources, unit);
    if (err < 0)
        return err;

    c->connected = false;
    mutex_init(&c->mutex);
    c->last_pcr_value = cpu_to_be32(0x80000000);
    c->pcr_index = ipcr_index;
    c->max_speed = (impr & IMPR_SPEED_MASK) >> IMPR_SPEED_SHIFT;
    if (c->max_speed == SCODE_BETA)
        c->max_speed += (impr & IMPR_XSPEED_MASK) >> IMPR_XSPEED_SHIFT;

    return 0;
}
EXPORT_SYMBOL(cmp_connection_init);

void cmp_connection_destroy(struct cmp_connection *c)
{
    WARN_ON(c->connected);
    mutex_destroy(&c->mutex);
    fw_iso_resources_destroy(&c->resources);
}
EXPORT_SYMBOL(cmp_connection_destroy);


static __be32 ipcr_set_modify(struct cmp_connection *c, __be32 ipcr)
{
    ipcr &= ~cpu_to_be32(IPCR_BCAST_CONN |
                 IPCR_P2P_CONN_MASK |
                 IPCR_CHANNEL_MASK);
    ipcr |= cpu_to_be32(1 << IPCR_P2P_CONN_SHIFT);
    ipcr |= cpu_to_be32(c->resources.channel << IPCR_CHANNEL_SHIFT);

    return ipcr;
}

static int ipcr_set_check(struct cmp_connection *c, __be32 ipcr)
{
    if (ipcr & cpu_to_be32(IPCR_BCAST_CONN |
                   IPCR_P2P_CONN_MASK)) {
        cmp_error(c, "plug is already in use\n");
        return -EBUSY;
    }
    if (!(ipcr & cpu_to_be32(IPCR_ONLINE))) {
        cmp_error(c, "plug is not on-line\n");
        return -ECONNREFUSED;
    }

    return 0;
}

int cmp_connection_establish(struct cmp_connection *c,
                 unsigned int max_payload_bytes)
{
    int err;

    if (WARN_ON(c->connected))
        return -EISCONN;

    c->speed = min(c->max_speed,
               fw_parent_device(c->resources.unit)->max_speed);

    mutex_lock(&c->mutex);

retry_after_bus_reset:
    err = fw_iso_resources_allocate(&c->resources,
                    max_payload_bytes, c->speed);
    if (err < 0)
        goto err_mutex;

    err = pcr_modify(c, ipcr_set_modify, ipcr_set_check,
             ABORT_ON_BUS_RESET);
    if (err == -EAGAIN) {
        fw_iso_resources_free(&c->resources);
        goto retry_after_bus_reset;
    }
    if (err < 0)
        goto err_resources;

    c->connected = true;

    mutex_unlock(&c->mutex);

    return 0;

err_resources:
    fw_iso_resources_free(&c->resources);
err_mutex:
    mutex_unlock(&c->mutex);

    return err;
}
EXPORT_SYMBOL(cmp_connection_establish);

int cmp_connection_update(struct cmp_connection *c)
{
    int err;

    mutex_lock(&c->mutex);

    if (!c->connected) {
        mutex_unlock(&c->mutex);
        return 0;
    }

    err = fw_iso_resources_update(&c->resources);
    if (err < 0)
        goto err_unconnect;

    err = pcr_modify(c, ipcr_set_modify, ipcr_set_check,
             SUCCEED_ON_BUS_RESET);
    if (err < 0)
        goto err_resources;

    mutex_unlock(&c->mutex);

    return 0;

err_resources:
    fw_iso_resources_free(&c->resources);
err_unconnect:
    c->connected = false;
    mutex_unlock(&c->mutex);

    return err;
}
EXPORT_SYMBOL(cmp_connection_update);


static __be32 ipcr_break_modify(struct cmp_connection *c, __be32 ipcr)
{
    return ipcr & ~cpu_to_be32(IPCR_BCAST_CONN | IPCR_P2P_CONN_MASK);
}

void cmp_connection_break(struct cmp_connection *c)
{
    int err;

    mutex_lock(&c->mutex);

    if (!c->connected) {
        mutex_unlock(&c->mutex);
        return;
    }

    err = pcr_modify(c, ipcr_break_modify, NULL, SUCCEED_ON_BUS_RESET);
    if (err < 0)
        cmp_error(c, "plug is still connected\n");

    fw_iso_resources_free(&c->resources);

    c->connected = false;

    mutex_unlock(&c->mutex);
}
EXPORT_SYMBOL(cmp_connection_break);