/*
 * AM824 format in Audio and Music Data Transmission Protocol (IEC 61883-6)
 *
 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
 * Copyright (c) 2015 Takashi Sakamoto <o-takashi@sakamocchi.jp>
 *
 * Licensed under the terms of the GNU General Public License, version 2.
 */

#include <linux/slab.h>

#include "amdtp-am824.h"

#define CIP_FMT_AM              0x10

/* "Clock-based rate control mode" is just supported. */
#define AMDTP_FDF_AM824         0x00

/*
 * Nominally 3125 bytes/second, but the MIDI port's clock might be
 * 1% too slow, and the bus clock 100 ppm too fast.
 */
#define MIDI_BYTES_PER_SECOND   3093

/*
 * Several devices look only at the first eight data blocks.
 * In any case, this is more than enough for the MIDI data rate.
 */
#define MAX_MIDI_RX_BLOCKS      8

struct amdtp_am824 {
        struct snd_rawmidi_substream *midi[AM824_MAX_CHANNELS_FOR_MIDI * 8];
        int midi_fifo_limit;
        int midi_fifo_used[AM824_MAX_CHANNELS_FOR_MIDI * 8];
        unsigned int pcm_channels;
        unsigned int midi_ports;

        u8 pcm_positions[AM824_MAX_CHANNELS_FOR_PCM];
        u8 midi_position;

        unsigned int frame_multiplier;
};

/**
 * amdtp_am824_set_parameters - set stream parameters
 * @s: the AMDTP stream to configure
 * @rate: the sample rate
 * @pcm_channels: the number of PCM samples in each data block, to be encoded
 *                as AM824 multi-bit linear audio
 * @midi_ports: the number of MIDI ports (i.e., MPX-MIDI Data Channels)
 * @double_pcm_frames: one data block transfers two PCM frames
 *
 * The parameters must be set before the stream is started, and must not be
 * changed while the stream is running.
 */
int amdtp_am824_set_parameters(struct amdtp_stream *s, unsigned int rate,
                               unsigned int pcm_channels,
                               unsigned int midi_ports,
                               bool double_pcm_frames)
{
        struct amdtp_am824 *p = s->protocol;
        unsigned int midi_channels;
        unsigned int i;
        int err;

        if (amdtp_stream_running(s))
                return -EINVAL;

        if (pcm_channels > AM824_MAX_CHANNELS_FOR_PCM)
                return -EINVAL;

        midi_channels = DIV_ROUND_UP(midi_ports, 8);
        if (midi_channels > AM824_MAX_CHANNELS_FOR_MIDI)
                return -EINVAL;

        if (WARN_ON(amdtp_stream_running(s)) ||
            WARN_ON(pcm_channels > AM824_MAX_CHANNELS_FOR_PCM) ||
            WARN_ON(midi_channels > AM824_MAX_CHANNELS_FOR_MIDI))
                return -EINVAL;

        err = amdtp_stream_set_parameters(s, rate,
                                          pcm_channels + midi_channels);
        if (err < 0)
                return err;

        s->fdf = AMDTP_FDF_AM824 | s->sfc;

        p->pcm_channels = pcm_channels;
        p->midi_ports = midi_ports;

        /*
         * In IEC 61883-6, one data block represents one event. In ALSA, one
         * event equals to one PCM frame. But Dice has a quirk at higher
         * sampling rate to transfer two PCM frames in one data block.
         */
        if (double_pcm_frames)
                p->frame_multiplier = 2;
        else
                p->frame_multiplier = 1;

        /* init the position map for PCM and MIDI channels */
        for (i = 0; i < pcm_channels; i++)
                p->pcm_positions[i] = i;
        p->midi_position = p->pcm_channels;

        /*
         * We do not know the actual MIDI FIFO size of most devices.  Just
         * assume two bytes, i.e., one byte can be received over the bus while
         * the previous one is transmitted over MIDI.
         * (The value here is adjusted for midi_ratelimit_per_packet().)
         */
        p->midi_fifo_limit = rate - MIDI_BYTES_PER_SECOND * s->syt_interval + 1;

        return 0;
}
EXPORT_SYMBOL_GPL(amdtp_am824_set_parameters);

/**
 * amdtp_am824_set_pcm_position - set an index of data channel for a channel
 *                                of PCM frame
 * @s: the AMDTP stream
 * @index: the index of data channel in an data block
 * @position: the channel of PCM frame
 */
void amdtp_am824_set_pcm_position(struct amdtp_stream *s, unsigned int index,
                                 unsigned int position)
{
        struct amdtp_am824 *p = s->protocol;

        if (index < p->pcm_channels)
                p->pcm_positions[index] = position;
}
EXPORT_SYMBOL_GPL(amdtp_am824_set_pcm_position);

/**
 * amdtp_am824_set_midi_position - set a index of data channel for MIDI
 *                                 conformant data channel
 * @s: the AMDTP stream
 * @position: the index of data channel in an data block
 */
void amdtp_am824_set_midi_position(struct amdtp_stream *s,
                                   unsigned int position)
{
        struct amdtp_am824 *p = s->protocol;

        p->midi_position = position;
}
EXPORT_SYMBOL_GPL(amdtp_am824_set_midi_position);

static void write_pcm_s32(struct amdtp_stream *s,
                          struct snd_pcm_substream *pcm,
                          __be32 *buffer, unsigned int frames)
{
        struct amdtp_am824 *p = s->protocol;
        struct snd_pcm_runtime *runtime = pcm->runtime;
        unsigned int channels, remaining_frames, i, c;
        const u32 *src;

        channels = p->pcm_channels;
        src = (void *)runtime->dma_area +
                        frames_to_bytes(runtime, s->pcm_buffer_pointer);
        remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;

        for (i = 0; i < frames; ++i) {
                for (c = 0; c < channels; ++c) {
                        buffer[p->pcm_positions[c]] =
                                        cpu_to_be32((*src >> 8) | 0x40000000);
                        src++;
                }
                buffer += s->data_block_quadlets;
                if (--remaining_frames == 0)
                        src = (void *)runtime->dma_area;
        }
}

static void read_pcm_s32(struct amdtp_stream *s,
                         struct snd_pcm_substream *pcm,
                         __be32 *buffer, unsigned int frames)
{
        struct amdtp_am824 *p = s->protocol;
        struct snd_pcm_runtime *runtime = pcm->runtime;
        unsigned int channels, remaining_frames, i, c;
        u32 *dst;

        channels = p->pcm_channels;
        dst  = (void *)runtime->dma_area +
                        frames_to_bytes(runtime, s->pcm_buffer_pointer);
        remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;

        for (i = 0; i < frames; ++i) {
                for (c = 0; c < channels; ++c) {
                        *dst = be32_to_cpu(buffer[p->pcm_positions[c]]) << 8;
                        dst++;
                }
                buffer += s->data_block_quadlets;
                if (--remaining_frames == 0)
                        dst = (void *)runtime->dma_area;
        }
}

static void write_pcm_silence(struct amdtp_stream *s,
                              __be32 *buffer, unsigned int frames)
{
        struct amdtp_am824 *p = s->protocol;
        unsigned int i, c, channels = p->pcm_channels;

        for (i = 0; i < frames; ++i) {
                for (c = 0; c < channels; ++c)
                        buffer[p->pcm_positions[c]] = cpu_to_be32(0x40000000);
                buffer += s->data_block_quadlets;
        }
}

/**
 * amdtp_am824_add_pcm_hw_constraints - add hw constraints for PCM substream
 * @s:          the AMDTP stream for AM824 data block, must be initialized.
 * @runtime:    the PCM substream runtime
 *
 */
int amdtp_am824_add_pcm_hw_constraints(struct amdtp_stream *s,
                                       struct snd_pcm_runtime *runtime)
{
        int err;

        err = amdtp_stream_add_pcm_hw_constraints(s, runtime);
        if (err < 0)
                return err;

        /* AM824 in IEC 61883-6 can deliver 24bit data. */
        return snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
}
EXPORT_SYMBOL_GPL(amdtp_am824_add_pcm_hw_constraints);

/**
 * amdtp_am824_midi_trigger - start/stop playback/capture with a MIDI device
 * @s: the AMDTP stream
 * @port: index of MIDI port
 * @midi: the MIDI device to be started, or %NULL to stop the current device
 *
 * Call this function on a running isochronous stream to enable the actual
 * transmission of MIDI data.  This function should be called from the MIDI
 * device's .trigger callback.
 */
void amdtp_am824_midi_trigger(struct amdtp_stream *s, unsigned int port,
                              struct snd_rawmidi_substream *midi)
{
        struct amdtp_am824 *p = s->protocol;

        if (port < p->midi_ports)
                ACCESS_ONCE(p->midi[port]) = midi;
}
EXPORT_SYMBOL_GPL(amdtp_am824_midi_trigger);

/*
 * To avoid sending MIDI bytes at too high a rate, assume that the receiving
 * device has a FIFO, and track how much it is filled.  This values increases
 * by one whenever we send one byte in a packet, but the FIFO empties at
 * a constant rate independent of our packet rate.  One packet has syt_interval
 * samples, so the number of bytes that empty out of the FIFO, per packet(!),
 * is MIDI_BYTES_PER_SECOND * syt_interval / sample_rate.  To avoid storing
 * fractional values, the values in midi_fifo_used[] are measured in bytes
 * multiplied by the sample rate.
 */
static bool midi_ratelimit_per_packet(struct amdtp_stream *s, unsigned int port)
{
        struct amdtp_am824 *p = s->protocol;
        int used;

        used = p->midi_fifo_used[port];
        if (used == 0) /* common shortcut */
                return true;

        used -= MIDI_BYTES_PER_SECOND * s->syt_interval;
        used = max(used, 0);
        p->midi_fifo_used[port] = used;

        return used < p->midi_fifo_limit;
}

static void midi_rate_use_one_byte(struct amdtp_stream *s, unsigned int port)
{
        struct amdtp_am824 *p = s->protocol;

        p->midi_fifo_used[port] += amdtp_rate_table[s->sfc];
}

static void write_midi_messages(struct amdtp_stream *s, __be32 *buffer,
                                unsigned int frames)
{
        struct amdtp_am824 *p = s->protocol;
        unsigned int f, port;
        u8 *b;

        for (f = 0; f < frames; f++) {
                b = (u8 *)&buffer[p->midi_position];

                port = (s->data_block_counter + f) % 8;
                if (f < MAX_MIDI_RX_BLOCKS &&
                    midi_ratelimit_per_packet(s, port) &&
                    p->midi[port] != NULL &&
                    snd_rawmidi_transmit(p->midi[port], &b[1], 1) == 1) {
                        midi_rate_use_one_byte(s, port);
                        b[0] = 0x81;
                } else {
                        b[0] = 0x80;
                        b[1] = 0;
                }
                b[2] = 0;
                b[3] = 0;

                buffer += s->data_block_quadlets;
        }
}

static void read_midi_messages(struct amdtp_stream *s,
                               __be32 *buffer, unsigned int frames)
{
        struct amdtp_am824 *p = s->protocol;
        unsigned int f, port;
        int len;
        u8 *b;

        for (f = 0; f < frames; f++) {
                port = (s->data_block_counter + f) % 8;
                b = (u8 *)&buffer[p->midi_position];

                len = b[0] - 0x80;
                if ((1 <= len) &&  (len <= 3) && (p->midi[port]))
                        snd_rawmidi_receive(p->midi[port], b + 1, len);

                buffer += s->data_block_quadlets;
        }
}

static unsigned int process_rx_data_blocks(struct amdtp_stream *s, __be32 *buffer,
                                           unsigned int data_blocks, unsigned int *syt)
{
        struct amdtp_am824 *p = s->protocol;
        struct snd_pcm_substream *pcm = ACCESS_ONCE(s->pcm);
        unsigned int pcm_frames;

        if (pcm) {
                write_pcm_s32(s, pcm, buffer, data_blocks);
                pcm_frames = data_blocks * p->frame_multiplier;
        } else {
                write_pcm_silence(s, buffer, data_blocks);
                pcm_frames = 0;
        }

        if (p->midi_ports)
                write_midi_messages(s, buffer, data_blocks);

        return pcm_frames;
}

static unsigned int process_tx_data_blocks(struct amdtp_stream *s, __be32 *buffer,
                                           unsigned int data_blocks, unsigned int *syt)
{
        struct amdtp_am824 *p = s->protocol;
        struct snd_pcm_substream *pcm = ACCESS_ONCE(s->pcm);
        unsigned int pcm_frames;

        if (pcm) {
                read_pcm_s32(s, pcm, buffer, data_blocks);
                pcm_frames = data_blocks * p->frame_multiplier;
        } else {
                pcm_frames = 0;
        }

        if (p->midi_ports)
                read_midi_messages(s, buffer, data_blocks);

        return pcm_frames;
}

/**
 * amdtp_am824_init - initialize an AMDTP stream structure to handle AM824
 *                    data block
 * @s: the AMDTP stream to initialize
 * @unit: the target of the stream
 * @dir: the direction of stream
 * @flags: the packet transmission method to use
 */
int amdtp_am824_init(struct amdtp_stream *s, struct fw_unit *unit,
                     enum amdtp_stream_direction dir, enum cip_flags flags)
{
        amdtp_stream_process_data_blocks_t process_data_blocks;

        if (dir == AMDTP_IN_STREAM)
                process_data_blocks = process_tx_data_blocks;
        else
                process_data_blocks = process_rx_data_blocks;

        return amdtp_stream_init(s, unit, dir, flags, CIP_FMT_AM,
                                 process_data_blocks,
                                 sizeof(struct amdtp_am824));
}
EXPORT_SYMBOL_GPL(amdtp_am824_init);