Merge tag 'powerpc-5.11-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc...

[linux/fpc-iii.git] / sound / firewire / amdtp-stream.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Audio and Music Data Transmission Protocol (IEC 61883-6) streams
 * with Common Isochronous Packet (IEC 61883-1) headers
 *
 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
 */

#include <linux/device.h>
#include <linux/err.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include "amdtp-stream.h"

#define TICKS_PER_CYCLE         3072
#define CYCLES_PER_SECOND       8000
#define TICKS_PER_SECOND        (TICKS_PER_CYCLE * CYCLES_PER_SECOND)

#define OHCI_MAX_SECOND         8

/* Always support Linux tracing subsystem. */
#define CREATE_TRACE_POINTS
#include "amdtp-stream-trace.h"

#define TRANSFER_DELAY_TICKS    0x2e00 /* 479.17 microseconds */

/* isochronous header parameters */
#define ISO_DATA_LENGTH_SHIFT   16
#define TAG_NO_CIP_HEADER       0
#define TAG_CIP                 1

/* common isochronous packet header parameters */
#define CIP_EOH_SHIFT           31
#define CIP_EOH                 (1u << CIP_EOH_SHIFT)
#define CIP_EOH_MASK            0x80000000
#define CIP_SID_SHIFT           24
#define CIP_SID_MASK            0x3f000000
#define CIP_DBS_MASK            0x00ff0000
#define CIP_DBS_SHIFT           16
#define CIP_SPH_MASK            0x00000400
#define CIP_SPH_SHIFT           10
#define CIP_DBC_MASK            0x000000ff
#define CIP_FMT_SHIFT           24
#define CIP_FMT_MASK            0x3f000000
#define CIP_FDF_MASK            0x00ff0000
#define CIP_FDF_SHIFT           16
#define CIP_SYT_MASK            0x0000ffff
#define CIP_SYT_NO_INFO         0xffff

/* Audio and Music transfer protocol specific parameters */
#define CIP_FMT_AM              0x10
#define AMDTP_FDF_NO_DATA       0xff

// For iso header, tstamp and 2 CIP header.
#define IR_CTX_HEADER_SIZE_CIP          16
// For iso header and tstamp.
#define IR_CTX_HEADER_SIZE_NO_CIP       8
#define HEADER_TSTAMP_MASK      0x0000ffff

#define IT_PKT_HEADER_SIZE_CIP          8 // For 2 CIP header.
#define IT_PKT_HEADER_SIZE_NO_CIP       0 // Nothing.

static void pcm_period_work(struct work_struct *work);

/**
 * amdtp_stream_init - initialize an AMDTP stream structure
 * @s: the AMDTP stream to initialize
 * @unit: the target of the stream
 * @dir: the direction of stream
 * @flags: the packet transmission method to use
 * @fmt: the value of fmt field in CIP header
 * @process_ctx_payloads: callback handler to process payloads of isoc context
 * @protocol_size: the size to allocate newly for protocol
 */
int amdtp_stream_init(struct amdtp_stream *s, struct fw_unit *unit,
                      enum amdtp_stream_direction dir, enum cip_flags flags,
                      unsigned int fmt,
                      amdtp_stream_process_ctx_payloads_t process_ctx_payloads,
                      unsigned int protocol_size)
{
        if (process_ctx_payloads == NULL)
                return -EINVAL;

        s->protocol = kzalloc(protocol_size, GFP_KERNEL);
        if (!s->protocol)
                return -ENOMEM;

        s->unit = unit;
        s->direction = dir;
        s->flags = flags;
        s->context = ERR_PTR(-1);
        mutex_init(&s->mutex);
        INIT_WORK(&s->period_work, pcm_period_work);
        s->packet_index = 0;

        init_waitqueue_head(&s->callback_wait);
        s->callbacked = false;

        s->fmt = fmt;
        s->process_ctx_payloads = process_ctx_payloads;

        if (dir == AMDTP_OUT_STREAM)
                s->ctx_data.rx.syt_override = -1;

        return 0;
}
EXPORT_SYMBOL(amdtp_stream_init);

/**
 * amdtp_stream_destroy - free stream resources
 * @s: the AMDTP stream to destroy
 */
void amdtp_stream_destroy(struct amdtp_stream *s)
{
        /* Not initialized. */
        if (s->protocol == NULL)
                return;

        WARN_ON(amdtp_stream_running(s));
        kfree(s->protocol);
        mutex_destroy(&s->mutex);
}
EXPORT_SYMBOL(amdtp_stream_destroy);

const unsigned int amdtp_syt_intervals[CIP_SFC_COUNT] = {
        [CIP_SFC_32000]  =  8,
        [CIP_SFC_44100]  =  8,
        [CIP_SFC_48000]  =  8,
        [CIP_SFC_88200]  = 16,
        [CIP_SFC_96000]  = 16,
        [CIP_SFC_176400] = 32,
        [CIP_SFC_192000] = 32,
};
EXPORT_SYMBOL(amdtp_syt_intervals);

const unsigned int amdtp_rate_table[CIP_SFC_COUNT] = {
        [CIP_SFC_32000]  =  32000,
        [CIP_SFC_44100]  =  44100,
        [CIP_SFC_48000]  =  48000,
        [CIP_SFC_88200]  =  88200,
        [CIP_SFC_96000]  =  96000,
        [CIP_SFC_176400] = 176400,
        [CIP_SFC_192000] = 192000,
};
EXPORT_SYMBOL(amdtp_rate_table);

static int apply_constraint_to_size(struct snd_pcm_hw_params *params,
                                    struct snd_pcm_hw_rule *rule)
{
        struct snd_interval *s = hw_param_interval(params, rule->var);
        const struct snd_interval *r =
                hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_RATE);
        struct snd_interval t = {0};
        unsigned int step = 0;
        int i;

        for (i = 0; i < CIP_SFC_COUNT; ++i) {
                if (snd_interval_test(r, amdtp_rate_table[i]))
                        step = max(step, amdtp_syt_intervals[i]);
        }

        t.min = roundup(s->min, step);
        t.max = rounddown(s->max, step);
        t.integer = 1;

        return snd_interval_refine(s, &t);
}

/**
 * amdtp_stream_add_pcm_hw_constraints - add hw constraints for PCM substream
 * @s:          the AMDTP stream, which must be initialized.
 * @runtime:    the PCM substream runtime
 */
int amdtp_stream_add_pcm_hw_constraints(struct amdtp_stream *s,
                                        struct snd_pcm_runtime *runtime)
{
        struct snd_pcm_hardware *hw = &runtime->hw;
        unsigned int ctx_header_size;
        unsigned int maximum_usec_per_period;
        int err;

        hw->info = SNDRV_PCM_INFO_BATCH |
                   SNDRV_PCM_INFO_BLOCK_TRANSFER |
                   SNDRV_PCM_INFO_INTERLEAVED |
                   SNDRV_PCM_INFO_JOINT_DUPLEX |
                   SNDRV_PCM_INFO_MMAP |
                   SNDRV_PCM_INFO_MMAP_VALID;

        /* SNDRV_PCM_INFO_BATCH */
        hw->periods_min = 2;
        hw->periods_max = UINT_MAX;

        /* bytes for a frame */
        hw->period_bytes_min = 4 * hw->channels_max;

        /* Just to prevent from allocating much pages. */
        hw->period_bytes_max = hw->period_bytes_min * 2048;
        hw->buffer_bytes_max = hw->period_bytes_max * hw->periods_min;

        // Linux driver for 1394 OHCI controller voluntarily flushes isoc
        // context when total size of accumulated context header reaches
        // PAGE_SIZE. This kicks work for the isoc context and brings
        // callback in the middle of scheduled interrupts.
        // Although AMDTP streams in the same domain use the same events per
        // IRQ, use the largest size of context header between IT/IR contexts.
        // Here, use the value of context header in IR context is for both
        // contexts.
        if (!(s->flags & CIP_NO_HEADER))
                ctx_header_size = IR_CTX_HEADER_SIZE_CIP;
        else
                ctx_header_size = IR_CTX_HEADER_SIZE_NO_CIP;
        maximum_usec_per_period = USEC_PER_SEC * PAGE_SIZE /
                                  CYCLES_PER_SECOND / ctx_header_size;

        // In IEC 61883-6, one isoc packet can transfer events up to the value
        // of syt interval. This comes from the interval of isoc cycle. As 1394
        // OHCI controller can generate hardware IRQ per isoc packet, the
        // interval is 125 usec.
        // However, there are two ways of transmission in IEC 61883-6; blocking
        // and non-blocking modes. In blocking mode, the sequence of isoc packet
        // includes 'empty' or 'NODATA' packets which include no event. In
        // non-blocking mode, the number of events per packet is variable up to
        // the syt interval.
        // Due to the above protocol design, the minimum PCM frames per
        // interrupt should be double of the value of syt interval, thus it is
        // 250 usec.
        err = snd_pcm_hw_constraint_minmax(runtime,
                                           SNDRV_PCM_HW_PARAM_PERIOD_TIME,
                                           250, maximum_usec_per_period);
        if (err < 0)
                goto end;

        /* Non-Blocking stream has no more constraints */
        if (!(s->flags & CIP_BLOCKING))
                goto end;

        /*
         * One AMDTP packet can include some frames. In blocking mode, the
         * number equals to SYT_INTERVAL. So the number is 8, 16 or 32,
         * depending on its sampling rate. For accurate period interrupt, it's
         * preferrable to align period/buffer sizes to current SYT_INTERVAL.
         */
        err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
                                  apply_constraint_to_size, NULL,
                                  SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
                                  SNDRV_PCM_HW_PARAM_RATE, -1);
        if (err < 0)
                goto end;
        err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_SIZE,
                                  apply_constraint_to_size, NULL,
                                  SNDRV_PCM_HW_PARAM_BUFFER_SIZE,
                                  SNDRV_PCM_HW_PARAM_RATE, -1);
        if (err < 0)
                goto end;
end:
        return err;
}
EXPORT_SYMBOL(amdtp_stream_add_pcm_hw_constraints);

/**
 * amdtp_stream_set_parameters - set stream parameters
 * @s: the AMDTP stream to configure
 * @rate: the sample rate
 * @data_block_quadlets: the size of a data block in quadlet unit
 *
 * The parameters must be set before the stream is started, and must not be
 * changed while the stream is running.
 */
int amdtp_stream_set_parameters(struct amdtp_stream *s, unsigned int rate,
                                unsigned int data_block_quadlets)
{
        unsigned int sfc;

        for (sfc = 0; sfc < ARRAY_SIZE(amdtp_rate_table); ++sfc) {
                if (amdtp_rate_table[sfc] == rate)
                        break;
        }
        if (sfc == ARRAY_SIZE(amdtp_rate_table))
                return -EINVAL;

        s->sfc = sfc;
        s->data_block_quadlets = data_block_quadlets;
        s->syt_interval = amdtp_syt_intervals[sfc];

        // default buffering in the device.
        if (s->direction == AMDTP_OUT_STREAM) {
                s->ctx_data.rx.transfer_delay =
                                        TRANSFER_DELAY_TICKS - TICKS_PER_CYCLE;

                if (s->flags & CIP_BLOCKING) {
                        // additional buffering needed to adjust for no-data
                        // packets.
                        s->ctx_data.rx.transfer_delay +=
                                TICKS_PER_SECOND * s->syt_interval / rate;
                }
        }

        return 0;
}
EXPORT_SYMBOL(amdtp_stream_set_parameters);

/**
 * amdtp_stream_get_max_payload - get the stream's packet size
 * @s: the AMDTP stream
 *
 * This function must not be called before the stream has been configured
 * with amdtp_stream_set_parameters().
 */
unsigned int amdtp_stream_get_max_payload(struct amdtp_stream *s)
{
        unsigned int multiplier = 1;
        unsigned int cip_header_size = 0;

        if (s->flags & CIP_JUMBO_PAYLOAD)
                multiplier = 5;
        if (!(s->flags & CIP_NO_HEADER))
                cip_header_size = sizeof(__be32) * 2;

        return cip_header_size +
                s->syt_interval * s->data_block_quadlets * sizeof(__be32) * multiplier;
}
EXPORT_SYMBOL(amdtp_stream_get_max_payload);

/**
 * amdtp_stream_pcm_prepare - prepare PCM device for running
 * @s: the AMDTP stream
 *
 * This function should be called from the PCM device's .prepare callback.
 */
void amdtp_stream_pcm_prepare(struct amdtp_stream *s)
{
        cancel_work_sync(&s->period_work);
        s->pcm_buffer_pointer = 0;
        s->pcm_period_pointer = 0;
}
EXPORT_SYMBOL(amdtp_stream_pcm_prepare);

static unsigned int calculate_data_blocks(unsigned int *data_block_state,
                                bool is_blocking, bool is_no_info,
                                unsigned int syt_interval, enum cip_sfc sfc)
{
        unsigned int data_blocks;

        /* Blocking mode. */
        if (is_blocking) {
                /* This module generate empty packet for 'no data'. */
                if (is_no_info)
                        data_blocks = 0;
                else
                        data_blocks = syt_interval;
        /* Non-blocking mode. */
        } else {
                if (!cip_sfc_is_base_44100(sfc)) {
                        // Sample_rate / 8000 is an integer, and precomputed.
                        data_blocks = *data_block_state;
                } else {
                        unsigned int phase = *data_block_state;

                /*
                 * This calculates the number of data blocks per packet so that
                 * 1) the overall rate is correct and exactly synchronized to
                 *    the bus clock, and
                 * 2) packets with a rounded-up number of blocks occur as early
                 *    as possible in the sequence (to prevent underruns of the
                 *    device's buffer).
                 */
                        if (sfc == CIP_SFC_44100)
                                /* 6 6 5 6 5 6 5 ... */
                                data_blocks = 5 + ((phase & 1) ^
                                                   (phase == 0 || phase >= 40));
                        else
                                /* 12 11 11 11 11 ... or 23 22 22 22 22 ... */
                                data_blocks = 11 * (sfc >> 1) + (phase == 0);
                        if (++phase >= (80 >> (sfc >> 1)))
                                phase = 0;
                        *data_block_state = phase;
                }
        }

        return data_blocks;
}

static unsigned int calculate_syt_offset(unsigned int *last_syt_offset,
                        unsigned int *syt_offset_state, enum cip_sfc sfc)
{
        unsigned int syt_offset;

        if (*last_syt_offset < TICKS_PER_CYCLE) {
                if (!cip_sfc_is_base_44100(sfc))
                        syt_offset = *last_syt_offset + *syt_offset_state;
                else {
                /*
                 * The time, in ticks, of the n'th SYT_INTERVAL sample is:
                 *   n * SYT_INTERVAL * 24576000 / sample_rate
                 * Modulo TICKS_PER_CYCLE, the difference between successive
                 * elements is about 1386.23.  Rounding the results of this
                 * formula to the SYT precision results in a sequence of
                 * differences that begins with:
                 *   1386 1386 1387 1386 1386 1386 1387 1386 1386 1386 1387 ...
                 * This code generates _exactly_ the same sequence.
                 */
                        unsigned int phase = *syt_offset_state;
                        unsigned int index = phase % 13;

                        syt_offset = *last_syt_offset;
                        syt_offset += 1386 + ((index && !(index & 3)) ||
                                              phase == 146);
                        if (++phase >= 147)
                                phase = 0;
                        *syt_offset_state = phase;
                }
        } else
                syt_offset = *last_syt_offset - TICKS_PER_CYCLE;
        *last_syt_offset = syt_offset;

        if (syt_offset >= TICKS_PER_CYCLE)
                syt_offset = CIP_SYT_NO_INFO;

        return syt_offset;
}

static void update_pcm_pointers(struct amdtp_stream *s,
                                struct snd_pcm_substream *pcm,
                                unsigned int frames)
{
        unsigned int ptr;

        ptr = s->pcm_buffer_pointer + frames;
        if (ptr >= pcm->runtime->buffer_size)
                ptr -= pcm->runtime->buffer_size;
        WRITE_ONCE(s->pcm_buffer_pointer, ptr);

        s->pcm_period_pointer += frames;
        if (s->pcm_period_pointer >= pcm->runtime->period_size) {
                s->pcm_period_pointer -= pcm->runtime->period_size;
                queue_work(system_highpri_wq, &s->period_work);
        }
}

static void pcm_period_work(struct work_struct *work)
{
        struct amdtp_stream *s = container_of(work, struct amdtp_stream,
                                              period_work);
        struct snd_pcm_substream *pcm = READ_ONCE(s->pcm);

        if (pcm)
                snd_pcm_period_elapsed(pcm);
}

static int queue_packet(struct amdtp_stream *s, struct fw_iso_packet *params,
                        bool sched_irq)
{
        int err;

        params->interrupt = sched_irq;
        params->tag = s->tag;
        params->sy = 0;

        err = fw_iso_context_queue(s->context, params, &s->buffer.iso_buffer,
                                   s->buffer.packets[s->packet_index].offset);
        if (err < 0) {
                dev_err(&s->unit->device, "queueing error: %d\n", err);
                goto end;
        }

        if (++s->packet_index >= s->queue_size)
                s->packet_index = 0;
end:
        return err;
}

static inline int queue_out_packet(struct amdtp_stream *s,
                                   struct fw_iso_packet *params, bool sched_irq)
{
        params->skip =
                !!(params->header_length == 0 && params->payload_length == 0);
        return queue_packet(s, params, sched_irq);
}

static inline int queue_in_packet(struct amdtp_stream *s,
                                  struct fw_iso_packet *params)
{
        // Queue one packet for IR context.
        params->header_length = s->ctx_data.tx.ctx_header_size;
        params->payload_length = s->ctx_data.tx.max_ctx_payload_length;
        params->skip = false;
        return queue_packet(s, params, false);
}

static void generate_cip_header(struct amdtp_stream *s, __be32 cip_header[2],
                        unsigned int data_block_counter, unsigned int syt)
{
        cip_header[0] = cpu_to_be32(READ_ONCE(s->source_node_id_field) |
                                (s->data_block_quadlets << CIP_DBS_SHIFT) |
                                ((s->sph << CIP_SPH_SHIFT) & CIP_SPH_MASK) |
                                data_block_counter);
        cip_header[1] = cpu_to_be32(CIP_EOH |
                        ((s->fmt << CIP_FMT_SHIFT) & CIP_FMT_MASK) |
                        ((s->ctx_data.rx.fdf << CIP_FDF_SHIFT) & CIP_FDF_MASK) |
                        (syt & CIP_SYT_MASK));
}

static void build_it_pkt_header(struct amdtp_stream *s, unsigned int cycle,
                                struct fw_iso_packet *params,
                                unsigned int data_blocks,
                                unsigned int data_block_counter,
                                unsigned int syt, unsigned int index)
{
        unsigned int payload_length;
        __be32 *cip_header;

        payload_length = data_blocks * sizeof(__be32) * s->data_block_quadlets;
        params->payload_length = payload_length;

        if (!(s->flags & CIP_NO_HEADER)) {
                cip_header = (__be32 *)params->header;
                generate_cip_header(s, cip_header, data_block_counter, syt);
                params->header_length = 2 * sizeof(__be32);
                payload_length += params->header_length;
        } else {
                cip_header = NULL;
        }

        trace_amdtp_packet(s, cycle, cip_header, payload_length, data_blocks,
                           data_block_counter, index);
}

static int check_cip_header(struct amdtp_stream *s, const __be32 *buf,
                            unsigned int payload_length,
                            unsigned int *data_blocks,
                            unsigned int *data_block_counter, unsigned int *syt)
{
        u32 cip_header[2];
        unsigned int sph;
        unsigned int fmt;
        unsigned int fdf;
        unsigned int dbc;
        bool lost;

        cip_header[0] = be32_to_cpu(buf[0]);
        cip_header[1] = be32_to_cpu(buf[1]);

        /*
         * This module supports 'Two-quadlet CIP header with SYT field'.
         * For convenience, also check FMT field is AM824 or not.
         */
        if ((((cip_header[0] & CIP_EOH_MASK) == CIP_EOH) ||
             ((cip_header[1] & CIP_EOH_MASK) != CIP_EOH)) &&
            (!(s->flags & CIP_HEADER_WITHOUT_EOH))) {
                dev_info_ratelimited(&s->unit->device,
                                "Invalid CIP header for AMDTP: %08X:%08X\n",
                                cip_header[0], cip_header[1]);
                return -EAGAIN;
        }

        /* Check valid protocol or not. */
        sph = (cip_header[0] & CIP_SPH_MASK) >> CIP_SPH_SHIFT;
        fmt = (cip_header[1] & CIP_FMT_MASK) >> CIP_FMT_SHIFT;
        if (sph != s->sph || fmt != s->fmt) {
                dev_info_ratelimited(&s->unit->device,
                                     "Detect unexpected protocol: %08x %08x\n",
                                     cip_header[0], cip_header[1]);
                return -EAGAIN;
        }

        /* Calculate data blocks */
        fdf = (cip_header[1] & CIP_FDF_MASK) >> CIP_FDF_SHIFT;
        if (payload_length < sizeof(__be32) * 2 ||
            (fmt == CIP_FMT_AM && fdf == AMDTP_FDF_NO_DATA)) {
                *data_blocks = 0;
        } else {
                unsigned int data_block_quadlets =
                                (cip_header[0] & CIP_DBS_MASK) >> CIP_DBS_SHIFT;
                /* avoid division by zero */
                if (data_block_quadlets == 0) {
                        dev_err(&s->unit->device,
                                "Detect invalid value in dbs field: %08X\n",
                                cip_header[0]);
                        return -EPROTO;
                }
                if (s->flags & CIP_WRONG_DBS)
                        data_block_quadlets = s->data_block_quadlets;

                *data_blocks = (payload_length / sizeof(__be32) - 2) /
                                                        data_block_quadlets;
        }

        /* Check data block counter continuity */
        dbc = cip_header[0] & CIP_DBC_MASK;
        if (*data_blocks == 0 && (s->flags & CIP_EMPTY_HAS_WRONG_DBC) &&
            *data_block_counter != UINT_MAX)
                dbc = *data_block_counter;

        if ((dbc == 0x00 && (s->flags & CIP_SKIP_DBC_ZERO_CHECK)) ||
            *data_block_counter == UINT_MAX) {
                lost = false;
        } else if (!(s->flags & CIP_DBC_IS_END_EVENT)) {
                lost = dbc != *data_block_counter;
        } else {
                unsigned int dbc_interval;

                if (*data_blocks > 0 && s->ctx_data.tx.dbc_interval > 0)
                        dbc_interval = s->ctx_data.tx.dbc_interval;
                else
                        dbc_interval = *data_blocks;

                lost = dbc != ((*data_block_counter + dbc_interval) & 0xff);
        }

        if (lost) {
                dev_err(&s->unit->device,
                        "Detect discontinuity of CIP: %02X %02X\n",
                        *data_block_counter, dbc);
                return -EIO;
        }

        *data_block_counter = dbc;

        *syt = cip_header[1] & CIP_SYT_MASK;

        return 0;
}

static int parse_ir_ctx_header(struct amdtp_stream *s, unsigned int cycle,
                               const __be32 *ctx_header,
                               unsigned int *payload_length,
                               unsigned int *data_blocks,
                               unsigned int *data_block_counter,
                               unsigned int *syt, unsigned int index)
{
        const __be32 *cip_header;
        int err;

        *payload_length = be32_to_cpu(ctx_header[0]) >> ISO_DATA_LENGTH_SHIFT;
        if (*payload_length > s->ctx_data.tx.ctx_header_size +
                                        s->ctx_data.tx.max_ctx_payload_length) {
                dev_err(&s->unit->device,
                        "Detect jumbo payload: %04x %04x\n",
                        *payload_length, s->ctx_data.tx.max_ctx_payload_length);
                return -EIO;
        }

        if (!(s->flags & CIP_NO_HEADER)) {
                cip_header = ctx_header + 2;
                err = check_cip_header(s, cip_header, *payload_length,
                                       data_blocks, data_block_counter, syt);
                if (err < 0)
                        return err;
        } else {
                cip_header = NULL;
                err = 0;
                *data_blocks = *payload_length / sizeof(__be32) /
                               s->data_block_quadlets;
                *syt = 0;

                if (*data_block_counter == UINT_MAX)
                        *data_block_counter = 0;
        }

        trace_amdtp_packet(s, cycle, cip_header, *payload_length, *data_blocks,
                           *data_block_counter, index);

        return err;
}

// In CYCLE_TIMER register of IEEE 1394, 7 bits are used to represent second. On
// the other hand, in DMA descriptors of 1394 OHCI, 3 bits are used to represent
// it. Thus, via Linux firewire subsystem, we can get the 3 bits for second.
static inline u32 compute_cycle_count(__be32 ctx_header_tstamp)
{
        u32 tstamp = be32_to_cpu(ctx_header_tstamp) & HEADER_TSTAMP_MASK;
        return (((tstamp >> 13) & 0x07) * 8000) + (tstamp & 0x1fff);
}

static inline u32 increment_cycle_count(u32 cycle, unsigned int addend)
{
        cycle += addend;
        if (cycle >= OHCI_MAX_SECOND * CYCLES_PER_SECOND)
                cycle -= OHCI_MAX_SECOND * CYCLES_PER_SECOND;
        return cycle;
}

// Align to actual cycle count for the packet which is going to be scheduled.
// This module queued the same number of isochronous cycle as the size of queue
// to kip isochronous cycle, therefore it's OK to just increment the cycle by
// the size of queue for scheduled cycle.
static inline u32 compute_it_cycle(const __be32 ctx_header_tstamp,
                                   unsigned int queue_size)
{
        u32 cycle = compute_cycle_count(ctx_header_tstamp);
        return increment_cycle_count(cycle, queue_size);
}

static int generate_device_pkt_descs(struct amdtp_stream *s,
                                     struct pkt_desc *descs,
                                     const __be32 *ctx_header,
                                     unsigned int packets)
{
        unsigned int dbc = s->data_block_counter;
        int i;
        int err;

        for (i = 0; i < packets; ++i) {
                struct pkt_desc *desc = descs + i;
                unsigned int index = (s->packet_index + i) % s->queue_size;
                unsigned int cycle;
                unsigned int payload_length;
                unsigned int data_blocks;
                unsigned int syt;

                cycle = compute_cycle_count(ctx_header[1]);

                err = parse_ir_ctx_header(s, cycle, ctx_header, &payload_length,
                                          &data_blocks, &dbc, &syt, i);
                if (err < 0)
                        return err;

                desc->cycle = cycle;
                desc->syt = syt;
                desc->data_blocks = data_blocks;
                desc->data_block_counter = dbc;
                desc->ctx_payload = s->buffer.packets[index].buffer;

                if (!(s->flags & CIP_DBC_IS_END_EVENT))
                        dbc = (dbc + desc->data_blocks) & 0xff;

                ctx_header +=
                        s->ctx_data.tx.ctx_header_size / sizeof(*ctx_header);
        }

        s->data_block_counter = dbc;

        return 0;
}

static unsigned int compute_syt(unsigned int syt_offset, unsigned int cycle,
                                unsigned int transfer_delay)
{
        unsigned int syt;

        syt_offset += transfer_delay;
        syt = ((cycle + syt_offset / TICKS_PER_CYCLE) << 12) |
              (syt_offset % TICKS_PER_CYCLE);
        return syt & CIP_SYT_MASK;
}

static void generate_pkt_descs(struct amdtp_stream *s, struct pkt_desc *descs,
                               const __be32 *ctx_header, unsigned int packets,
                               const struct seq_desc *seq_descs,
                               unsigned int seq_size)
{
        unsigned int dbc = s->data_block_counter;
        unsigned int seq_index = s->ctx_data.rx.seq_index;
        int i;

        for (i = 0; i < packets; ++i) {
                struct pkt_desc *desc = descs + i;
                unsigned int index = (s->packet_index + i) % s->queue_size;
                const struct seq_desc *seq = seq_descs + seq_index;
                unsigned int syt;

                desc->cycle = compute_it_cycle(*ctx_header, s->queue_size);

                syt = seq->syt_offset;
                if (syt != CIP_SYT_NO_INFO) {
                        syt = compute_syt(syt, desc->cycle,
                                          s->ctx_data.rx.transfer_delay);
                }
                desc->syt = syt;
                desc->data_blocks = seq->data_blocks;

                if (s->flags & CIP_DBC_IS_END_EVENT)
                        dbc = (dbc + desc->data_blocks) & 0xff;

                desc->data_block_counter = dbc;

                if (!(s->flags & CIP_DBC_IS_END_EVENT))
                        dbc = (dbc + desc->data_blocks) & 0xff;

                desc->ctx_payload = s->buffer.packets[index].buffer;

                seq_index = (seq_index + 1) % seq_size;

                ++ctx_header;
        }

        s->data_block_counter = dbc;
        s->ctx_data.rx.seq_index = seq_index;
}

static inline void cancel_stream(struct amdtp_stream *s)
{
        s->packet_index = -1;
        if (current_work() == &s->period_work)
                amdtp_stream_pcm_abort(s);
        WRITE_ONCE(s->pcm_buffer_pointer, SNDRV_PCM_POS_XRUN);
}

static void process_ctx_payloads(struct amdtp_stream *s,
                                 const struct pkt_desc *descs,
                                 unsigned int packets)
{
        struct snd_pcm_substream *pcm;
        unsigned int pcm_frames;

        pcm = READ_ONCE(s->pcm);
        pcm_frames = s->process_ctx_payloads(s, descs, packets, pcm);
        if (pcm)
                update_pcm_pointers(s, pcm, pcm_frames);
}

static void out_stream_callback(struct fw_iso_context *context, u32 tstamp,
                                size_t header_length, void *header,
                                void *private_data)
{
        struct amdtp_stream *s = private_data;
        const struct amdtp_domain *d = s->domain;
        const __be32 *ctx_header = header;
        unsigned int events_per_period = s->ctx_data.rx.events_per_period;
        unsigned int event_count = s->ctx_data.rx.event_count;
        unsigned int packets;
        int i;

        if (s->packet_index < 0)
                return;

        // Calculate the number of packets in buffer and check XRUN.
        packets = header_length / sizeof(*ctx_header);

        generate_pkt_descs(s, s->pkt_descs, ctx_header, packets, d->seq_descs,
                           d->seq_size);

        process_ctx_payloads(s, s->pkt_descs, packets);

        for (i = 0; i < packets; ++i) {
                const struct pkt_desc *desc = s->pkt_descs + i;
                unsigned int syt;
                struct {
                        struct fw_iso_packet params;
                        __be32 header[IT_PKT_HEADER_SIZE_CIP / sizeof(__be32)];
                } template = { {0}, {0} };
                bool sched_irq = false;

                if (s->ctx_data.rx.syt_override < 0)
                        syt = desc->syt;
                else
                        syt = s->ctx_data.rx.syt_override;

                build_it_pkt_header(s, desc->cycle, &template.params,
                                    desc->data_blocks, desc->data_block_counter,
                                    syt, i);

                if (s == s->domain->irq_target) {
                        event_count += desc->data_blocks;
                        if (event_count >= events_per_period) {
                                event_count -= events_per_period;
                                sched_irq = true;
                        }
                }

                if (queue_out_packet(s, &template.params, sched_irq) < 0) {
                        cancel_stream(s);
                        return;
                }
        }

        s->ctx_data.rx.event_count = event_count;
}

static void in_stream_callback(struct fw_iso_context *context, u32 tstamp,
                               size_t header_length, void *header,
                               void *private_data)
{
        struct amdtp_stream *s = private_data;
        __be32 *ctx_header = header;
        unsigned int packets;
        int i;
        int err;

        if (s->packet_index < 0)
                return;

        // Calculate the number of packets in buffer and check XRUN.
        packets = header_length / s->ctx_data.tx.ctx_header_size;

        err = generate_device_pkt_descs(s, s->pkt_descs, ctx_header, packets);
        if (err < 0) {
                if (err != -EAGAIN) {
                        cancel_stream(s);
                        return;
                }
        } else {
                process_ctx_payloads(s, s->pkt_descs, packets);
        }

        for (i = 0; i < packets; ++i) {
                struct fw_iso_packet params = {0};

                if (queue_in_packet(s, &params) < 0) {
                        cancel_stream(s);
                        return;
                }
        }
}

static void pool_ideal_seq_descs(struct amdtp_domain *d, unsigned int packets)
{
        struct amdtp_stream *irq_target = d->irq_target;
        unsigned int seq_tail = d->seq_tail;
        unsigned int seq_size = d->seq_size;
        unsigned int min_avail;
        struct amdtp_stream *s;

        min_avail = d->seq_size;
        list_for_each_entry(s, &d->streams, list) {
                unsigned int seq_index;
                unsigned int avail;

                if (s->direction == AMDTP_IN_STREAM)
                        continue;

                seq_index = s->ctx_data.rx.seq_index;
                avail = d->seq_tail;
                if (seq_index > avail)
                        avail += d->seq_size;
                avail -= seq_index;

                if (avail < min_avail)
                        min_avail = avail;
        }

        while (min_avail < packets) {
                struct seq_desc *desc = d->seq_descs + seq_tail;

                desc->syt_offset = calculate_syt_offset(&d->last_syt_offset,
                                        &d->syt_offset_state, irq_target->sfc);
                desc->data_blocks = calculate_data_blocks(&d->data_block_state,
                                !!(irq_target->flags & CIP_BLOCKING),
                                desc->syt_offset == CIP_SYT_NO_INFO,
                                irq_target->syt_interval, irq_target->sfc);

                ++seq_tail;
                seq_tail %= seq_size;

                ++min_avail;
        }

        d->seq_tail = seq_tail;
}

static void irq_target_callback(struct fw_iso_context *context, u32 tstamp,
                                size_t header_length, void *header,
                                void *private_data)
{
        struct amdtp_stream *irq_target = private_data;
        struct amdtp_domain *d = irq_target->domain;
        unsigned int packets = header_length / sizeof(__be32);
        struct amdtp_stream *s;

        // Record enough entries with extra 3 cycles at least.
        pool_ideal_seq_descs(d, packets + 3);

        out_stream_callback(context, tstamp, header_length, header, irq_target);
        if (amdtp_streaming_error(irq_target))
                goto error;

        list_for_each_entry(s, &d->streams, list) {
                if (s != irq_target && amdtp_stream_running(s)) {
                        fw_iso_context_flush_completions(s->context);
                        if (amdtp_streaming_error(s))
                                goto error;
                }
        }

        return;
error:
        if (amdtp_stream_running(irq_target))
                cancel_stream(irq_target);

        list_for_each_entry(s, &d->streams, list) {
                if (amdtp_stream_running(s))
                        cancel_stream(s);
        }
}

// this is executed one time.
static void amdtp_stream_first_callback(struct fw_iso_context *context,
                                        u32 tstamp, size_t header_length,
                                        void *header, void *private_data)
{
        struct amdtp_stream *s = private_data;
        const __be32 *ctx_header = header;
        u32 cycle;

        /*
         * For in-stream, first packet has come.
         * For out-stream, prepared to transmit first packet
         */
        s->callbacked = true;
        wake_up(&s->callback_wait);

        if (s->direction == AMDTP_IN_STREAM) {
                cycle = compute_cycle_count(ctx_header[1]);

                context->callback.sc = in_stream_callback;
        } else {
                cycle = compute_it_cycle(*ctx_header, s->queue_size);

                if (s == s->domain->irq_target)
                        context->callback.sc = irq_target_callback;
                else
                        context->callback.sc = out_stream_callback;
        }

        s->start_cycle = cycle;

        context->callback.sc(context, tstamp, header_length, header, s);
}

/**
 * amdtp_stream_start - start transferring packets
 * @s: the AMDTP stream to start
 * @channel: the isochronous channel on the bus
 * @speed: firewire speed code
 * @start_cycle: the isochronous cycle to start the context. Start immediately
 *               if negative value is given.
 * @queue_size: The number of packets in the queue.
 * @idle_irq_interval: the interval to queue packet during initial state.
 *
 * The stream cannot be started until it has been configured with
 * amdtp_stream_set_parameters() and it must be started before any PCM or MIDI
 * device can be started.
 */
static int amdtp_stream_start(struct amdtp_stream *s, int channel, int speed,
                              int start_cycle, unsigned int queue_size,
                              unsigned int idle_irq_interval)
{
        bool is_irq_target = (s == s->domain->irq_target);
        unsigned int ctx_header_size;
        unsigned int max_ctx_payload_size;
        enum dma_data_direction dir;
        int type, tag, err;

        mutex_lock(&s->mutex);

        if (WARN_ON(amdtp_stream_running(s) ||
                    (s->data_block_quadlets < 1))) {
                err = -EBADFD;
                goto err_unlock;
        }

        if (s->direction == AMDTP_IN_STREAM) {
                // NOTE: IT context should be used for constant IRQ.
                if (is_irq_target) {
                        err = -EINVAL;
                        goto err_unlock;
                }

                s->data_block_counter = UINT_MAX;
        } else {
                s->data_block_counter = 0;
        }

        /* initialize packet buffer */
        if (s->direction == AMDTP_IN_STREAM) {
                dir = DMA_FROM_DEVICE;
                type = FW_ISO_CONTEXT_RECEIVE;
                if (!(s->flags & CIP_NO_HEADER))
                        ctx_header_size = IR_CTX_HEADER_SIZE_CIP;
                else
                        ctx_header_size = IR_CTX_HEADER_SIZE_NO_CIP;

                max_ctx_payload_size = amdtp_stream_get_max_payload(s) -
                                       ctx_header_size;
        } else {
                dir = DMA_TO_DEVICE;
                type = FW_ISO_CONTEXT_TRANSMIT;
                ctx_header_size = 0;    // No effect for IT context.

                max_ctx_payload_size = amdtp_stream_get_max_payload(s);
                if (!(s->flags & CIP_NO_HEADER))
                        max_ctx_payload_size -= IT_PKT_HEADER_SIZE_CIP;
        }

        err = iso_packets_buffer_init(&s->buffer, s->unit, queue_size,
                                      max_ctx_payload_size, dir);
        if (err < 0)
                goto err_unlock;
        s->queue_size = queue_size;

        s->context = fw_iso_context_create(fw_parent_device(s->unit)->card,
                                          type, channel, speed, ctx_header_size,
                                          amdtp_stream_first_callback, s);
        if (IS_ERR(s->context)) {
                err = PTR_ERR(s->context);
                if (err == -EBUSY)
                        dev_err(&s->unit->device,
                                "no free stream on this controller\n");
                goto err_buffer;
        }

        amdtp_stream_update(s);

        if (s->direction == AMDTP_IN_STREAM) {
                s->ctx_data.tx.max_ctx_payload_length = max_ctx_payload_size;
                s->ctx_data.tx.ctx_header_size = ctx_header_size;
        }

        if (s->flags & CIP_NO_HEADER)
                s->tag = TAG_NO_CIP_HEADER;
        else
                s->tag = TAG_CIP;

        s->pkt_descs = kcalloc(s->queue_size, sizeof(*s->pkt_descs),
                               GFP_KERNEL);
        if (!s->pkt_descs) {
                err = -ENOMEM;
                goto err_context;
        }

        s->packet_index = 0;
        do {
                struct fw_iso_packet params;

                if (s->direction == AMDTP_IN_STREAM) {
                        err = queue_in_packet(s, &params);
                } else {
                        bool sched_irq = false;

                        params.header_length = 0;
                        params.payload_length = 0;

                        if (is_irq_target) {
                                sched_irq = !((s->packet_index + 1) %
                                              idle_irq_interval);
                        }

                        err = queue_out_packet(s, &params, sched_irq);
                }
                if (err < 0)
                        goto err_pkt_descs;
        } while (s->packet_index > 0);

        /* NOTE: TAG1 matches CIP. This just affects in stream. */
        tag = FW_ISO_CONTEXT_MATCH_TAG1;
        if ((s->flags & CIP_EMPTY_WITH_TAG0) || (s->flags & CIP_NO_HEADER))
                tag |= FW_ISO_CONTEXT_MATCH_TAG0;

        s->callbacked = false;
        err = fw_iso_context_start(s->context, start_cycle, 0, tag);
        if (err < 0)
                goto err_pkt_descs;

        mutex_unlock(&s->mutex);

        return 0;
err_pkt_descs:
        kfree(s->pkt_descs);
err_context:
        fw_iso_context_destroy(s->context);
        s->context = ERR_PTR(-1);
err_buffer:
        iso_packets_buffer_destroy(&s->buffer, s->unit);
err_unlock:
        mutex_unlock(&s->mutex);

        return err;
}

/**
 * amdtp_domain_stream_pcm_pointer - get the PCM buffer position
 * @d: the AMDTP domain.
 * @s: the AMDTP stream that transports the PCM data
 *
 * Returns the current buffer position, in frames.
 */
unsigned long amdtp_domain_stream_pcm_pointer(struct amdtp_domain *d,
                                              struct amdtp_stream *s)
{
        struct amdtp_stream *irq_target = d->irq_target;

        if (irq_target && amdtp_stream_running(irq_target)) {
                // This function is called in software IRQ context of
                // period_work or process context.
                //
                // When the software IRQ context was scheduled by software IRQ
                // context of IT contexts, queued packets were already handled.
                // Therefore, no need to flush the queue in buffer furthermore.
                //
                // When the process context reach here, some packets will be
                // already queued in the buffer. These packets should be handled
                // immediately to keep better granularity of PCM pointer.
                //
                // Later, the process context will sometimes schedules software
                // IRQ context of the period_work. Then, no need to flush the
                // queue by the same reason as described in the above
                if (current_work() != &s->period_work) {
                        // Queued packet should be processed without any kernel
                        // preemption to keep latency against bus cycle.
                        preempt_disable();
                        fw_iso_context_flush_completions(irq_target->context);
                        preempt_enable();
                }
        }

        return READ_ONCE(s->pcm_buffer_pointer);
}
EXPORT_SYMBOL_GPL(amdtp_domain_stream_pcm_pointer);

/**
 * amdtp_domain_stream_pcm_ack - acknowledge queued PCM frames
 * @d: the AMDTP domain.
 * @s: the AMDTP stream that transfers the PCM frames
 *
 * Returns zero always.
 */
int amdtp_domain_stream_pcm_ack(struct amdtp_domain *d, struct amdtp_stream *s)
{
        struct amdtp_stream *irq_target = d->irq_target;

        // Process isochronous packets for recent isochronous cycle to handle
        // queued PCM frames.
        if (irq_target && amdtp_stream_running(irq_target)) {
                // Queued packet should be processed without any kernel
                // preemption to keep latency against bus cycle.
                preempt_disable();
                fw_iso_context_flush_completions(irq_target->context);
                preempt_enable();
        }

        return 0;
}
EXPORT_SYMBOL_GPL(amdtp_domain_stream_pcm_ack);

/**
 * amdtp_stream_update - update the stream after a bus reset
 * @s: the AMDTP stream
 */
void amdtp_stream_update(struct amdtp_stream *s)
{
        /* Precomputing. */
        WRITE_ONCE(s->source_node_id_field,
                   (fw_parent_device(s->unit)->card->node_id << CIP_SID_SHIFT) & CIP_SID_MASK);
}
EXPORT_SYMBOL(amdtp_stream_update);

/**
 * amdtp_stream_stop - stop sending packets
 * @s: the AMDTP stream to stop
 *
 * All PCM and MIDI devices of the stream must be stopped before the stream
 * itself can be stopped.
 */
static void amdtp_stream_stop(struct amdtp_stream *s)
{
        mutex_lock(&s->mutex);

        if (!amdtp_stream_running(s)) {
                mutex_unlock(&s->mutex);
                return;
        }

        cancel_work_sync(&s->period_work);
        fw_iso_context_stop(s->context);
        fw_iso_context_destroy(s->context);
        s->context = ERR_PTR(-1);
        iso_packets_buffer_destroy(&s->buffer, s->unit);
        kfree(s->pkt_descs);

        s->callbacked = false;

        mutex_unlock(&s->mutex);
}

/**
 * amdtp_stream_pcm_abort - abort the running PCM device
 * @s: the AMDTP stream about to be stopped
 *
 * If the isochronous stream needs to be stopped asynchronously, call this
 * function first to stop the PCM device.
 */
void amdtp_stream_pcm_abort(struct amdtp_stream *s)
{
        struct snd_pcm_substream *pcm;

        pcm = READ_ONCE(s->pcm);
        if (pcm)
                snd_pcm_stop_xrun(pcm);
}
EXPORT_SYMBOL(amdtp_stream_pcm_abort);

/**
 * amdtp_domain_init - initialize an AMDTP domain structure
 * @d: the AMDTP domain to initialize.
 */
int amdtp_domain_init(struct amdtp_domain *d)
{
        INIT_LIST_HEAD(&d->streams);

        d->events_per_period = 0;

        d->seq_descs = NULL;

        return 0;
}
EXPORT_SYMBOL_GPL(amdtp_domain_init);

/**
 * amdtp_domain_destroy - destroy an AMDTP domain structure
 * @d: the AMDTP domain to destroy.
 */
void amdtp_domain_destroy(struct amdtp_domain *d)
{
        // At present nothing to do.
        return;
}
EXPORT_SYMBOL_GPL(amdtp_domain_destroy);

/**
 * amdtp_domain_add_stream - register isoc context into the domain.
 * @d: the AMDTP domain.
 * @s: the AMDTP stream.
 * @channel: the isochronous channel on the bus.
 * @speed: firewire speed code.
 */
int amdtp_domain_add_stream(struct amdtp_domain *d, struct amdtp_stream *s,
                            int channel, int speed)
{
        struct amdtp_stream *tmp;

        list_for_each_entry(tmp, &d->streams, list) {
                if (s == tmp)
                        return -EBUSY;
        }

        list_add(&s->list, &d->streams);

        s->channel = channel;
        s->speed = speed;
        s->domain = d;

        return 0;
}
EXPORT_SYMBOL_GPL(amdtp_domain_add_stream);

static int get_current_cycle_time(struct fw_card *fw_card, int *cur_cycle)
{
        int generation;
        int rcode;
        __be32 reg;
        u32 data;

        // This is a request to local 1394 OHCI controller and expected to
        // complete without any event waiting.
        generation = fw_card->generation;
        smp_rmb();      // node_id vs. generation.
        rcode = fw_run_transaction(fw_card, TCODE_READ_QUADLET_REQUEST,
                                   fw_card->node_id, generation, SCODE_100,
                                   CSR_REGISTER_BASE + CSR_CYCLE_TIME,
                                   &reg, sizeof(reg));
        if (rcode != RCODE_COMPLETE)
                return -EIO;

        data = be32_to_cpu(reg);
        *cur_cycle = data >> 12;

        return 0;
}

/**
 * amdtp_domain_start - start sending packets for isoc context in the domain.
 * @d: the AMDTP domain.
 * @ir_delay_cycle: the cycle delay to start all IR contexts.
 */
int amdtp_domain_start(struct amdtp_domain *d, unsigned int ir_delay_cycle)
{
        static const struct {
                unsigned int data_block;
                unsigned int syt_offset;
        } *entry, initial_state[] = {
                [CIP_SFC_32000]  = {  4, 3072 },
                [CIP_SFC_48000]  = {  6, 1024 },
                [CIP_SFC_96000]  = { 12, 1024 },
                [CIP_SFC_192000] = { 24, 1024 },
                [CIP_SFC_44100]  = {  0,   67 },
                [CIP_SFC_88200]  = {  0,   67 },
                [CIP_SFC_176400] = {  0,   67 },
        };
        unsigned int events_per_buffer = d->events_per_buffer;
        unsigned int events_per_period = d->events_per_period;
        unsigned int idle_irq_interval;
        unsigned int queue_size;
        struct amdtp_stream *s;
        int cycle;
        int err;

        // Select an IT context as IRQ target.
        list_for_each_entry(s, &d->streams, list) {
                if (s->direction == AMDTP_OUT_STREAM)
                        break;
        }
        if (!s)
                return -ENXIO;
        d->irq_target = s;

        // This is a case that AMDTP streams in domain run just for MIDI
        // substream. Use the number of events equivalent to 10 msec as
        // interval of hardware IRQ.
        if (events_per_period == 0)
                events_per_period = amdtp_rate_table[d->irq_target->sfc] / 100;
        if (events_per_buffer == 0)
                events_per_buffer = events_per_period * 3;

        queue_size = DIV_ROUND_UP(CYCLES_PER_SECOND * events_per_buffer,
                                  amdtp_rate_table[d->irq_target->sfc]);

        d->seq_descs = kcalloc(queue_size, sizeof(*d->seq_descs), GFP_KERNEL);
        if (!d->seq_descs)
                return -ENOMEM;
        d->seq_size = queue_size;
        d->seq_tail = 0;

        entry = &initial_state[s->sfc];
        d->data_block_state = entry->data_block;
        d->syt_offset_state = entry->syt_offset;
        d->last_syt_offset = TICKS_PER_CYCLE;

        if (ir_delay_cycle > 0) {
                struct fw_card *fw_card = fw_parent_device(s->unit)->card;

                err = get_current_cycle_time(fw_card, &cycle);
                if (err < 0)
                        goto error;

                // No need to care overflow in cycle field because of enough
                // width.
                cycle += ir_delay_cycle;

                // Round up to sec field.
                if ((cycle & 0x00001fff) >= CYCLES_PER_SECOND) {
                        unsigned int sec;

                        // The sec field can overflow.
                        sec = (cycle & 0xffffe000) >> 13;
                        cycle = (++sec << 13) |
                                ((cycle & 0x00001fff) / CYCLES_PER_SECOND);
                }

                // In OHCI 1394 specification, lower 2 bits are available for
                // sec field.
                cycle &= 0x00007fff;
        } else {
                cycle = -1;
        }

        list_for_each_entry(s, &d->streams, list) {
                int cycle_match;

                if (s->direction == AMDTP_IN_STREAM) {
                        cycle_match = cycle;
                } else {
                        // IT context starts immediately.
                        cycle_match = -1;
                        s->ctx_data.rx.seq_index = 0;
                }

                if (s != d->irq_target) {
                        err = amdtp_stream_start(s, s->channel, s->speed,
                                                 cycle_match, queue_size, 0);
                        if (err < 0)
                                goto error;
                }
        }

        s = d->irq_target;
        s->ctx_data.rx.events_per_period = events_per_period;
        s->ctx_data.rx.event_count = 0;
        s->ctx_data.rx.seq_index = 0;

        idle_irq_interval = DIV_ROUND_UP(CYCLES_PER_SECOND * events_per_period,
                                         amdtp_rate_table[d->irq_target->sfc]);
        err = amdtp_stream_start(s, s->channel, s->speed, -1, queue_size,
                                 idle_irq_interval);
        if (err < 0)
                goto error;

        return 0;
error:
        list_for_each_entry(s, &d->streams, list)
                amdtp_stream_stop(s);
        kfree(d->seq_descs);
        d->seq_descs = NULL;
        return err;
}
EXPORT_SYMBOL_GPL(amdtp_domain_start);

/**
 * amdtp_domain_stop - stop sending packets for isoc context in the same domain.
 * @d: the AMDTP domain to which the isoc contexts belong.
 */
void amdtp_domain_stop(struct amdtp_domain *d)
{
        struct amdtp_stream *s, *next;

        if (d->irq_target)
                amdtp_stream_stop(d->irq_target);

        list_for_each_entry_safe(s, next, &d->streams, list) {
                list_del(&s->list);

                if (s != d->irq_target)
                        amdtp_stream_stop(s);
        }

        d->events_per_period = 0;
        d->irq_target = NULL;

        kfree(d->seq_descs);
        d->seq_descs = NULL;
}
EXPORT_SYMBOL_GPL(amdtp_domain_stop);