// SPDX-License-Identifier: GPL-2.0-only
/*
 * amdtp-dot.c - a part of driver for Digidesign Digi 002/003 family
 *
 * Copyright (c) 2014-2015 Takashi Sakamoto
 * Copyright (C) 2012 Robin Gareus <robin@gareus.org>
 * Copyright (C) 2012 Damien Zammit <damien@zamaudio.com>
 */

#include <sound/pcm.h>
#include "digi00x.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

/* 3 = MAX(DOT_MIDI_IN_PORTS, DOT_MIDI_OUT_PORTS) + 1. */
#define MAX_MIDI_PORTS          3

/*
 * The double-oh-three algorithm was discovered by Robin Gareus and Damien
 * Zammit in 2012, with reverse-engineering for Digi 003 Rack.
 */
struct dot_state {
        u8 carry;
        u8 idx;
        unsigned int off;
};

struct amdtp_dot {
        unsigned int pcm_channels;
        struct dot_state state;

        struct snd_rawmidi_substream *midi[MAX_MIDI_PORTS];
        int midi_fifo_used[MAX_MIDI_PORTS];
        int midi_fifo_limit;
};

/*
 * double-oh-three look up table
 *
 * @param idx index byte (audio-sample data) 0x00..0xff
 * @param off channel offset shift
 * @return salt to XOR with given data
 */
#define BYTE_PER_SAMPLE (4)
#define MAGIC_DOT_BYTE (2)
#define MAGIC_BYTE_OFF(x) (((x) * BYTE_PER_SAMPLE) + MAGIC_DOT_BYTE)
static u8 dot_scrt(const u8 idx, const unsigned int off)
{
        /*
         * the length of the added pattern only depends on the lower nibble
         * of the last non-zero data
         */
        static const u8 len[16] = {0, 1, 3, 5, 7, 9, 11, 13, 14,
                                   12, 10, 8, 6, 4, 2, 0};

        /*
         * the lower nibble of the salt. Interleaved sequence.
         * this is walked backwards according to len[]
         */
        static const u8 nib[15] = {0x8, 0x7, 0x9, 0x6, 0xa, 0x5, 0xb, 0x4,
                                   0xc, 0x3, 0xd, 0x2, 0xe, 0x1, 0xf};

        /* circular list for the salt's hi nibble. */
        static const u8 hir[15] = {0x0, 0x6, 0xf, 0x8, 0x7, 0x5, 0x3, 0x4,
                                   0xc, 0xd, 0xe, 0x1, 0x2, 0xb, 0xa};

        /*
         * start offset for upper nibble mapping.
         * note: 9 is /special/. In the case where the high nibble == 0x9,
         * hir[] is not used and - coincidentally - the salt's hi nibble is
         * 0x09 regardless of the offset.
         */
        static const u8 hio[16] = {0, 11, 12, 6, 7, 5, 1, 4,
                                   3, 0x00, 14, 13, 8, 9, 10, 2};

        const u8 ln = idx & 0xf;
        const u8 hn = (idx >> 4) & 0xf;
        const u8 hr = (hn == 0x9) ? 0x9 : hir[(hio[hn] + off) % 15];

        if (len[ln] < off)
                return 0x00;

        return ((nib[14 + off - len[ln]]) | (hr << 4));
}

static void dot_encode_step(struct dot_state *state, __be32 *const buffer)
{
        u8 * const data = (u8 *) buffer;

        if (data[MAGIC_DOT_BYTE] != 0x00) {
                state->off = 0;
                state->idx = data[MAGIC_DOT_BYTE] ^ state->carry;
        }
        data[MAGIC_DOT_BYTE] ^= state->carry;
        state->carry = dot_scrt(state->idx, ++(state->off));
}

int amdtp_dot_set_parameters(struct amdtp_stream *s, unsigned int rate,
                             unsigned int pcm_channels)
{
        struct amdtp_dot *p = s->protocol;
        int err;

        if (amdtp_stream_running(s))
                return -EBUSY;

        /*
         * A first data channel is for MIDI messages, the rest is Multi Bit
         * Linear Audio data channel.
         */
        err = amdtp_stream_set_parameters(s, rate, pcm_channels + 1);
        if (err < 0)
                return err;

        s->ctx_data.rx.fdf = AMDTP_FDF_AM824 | s->sfc;

        p->pcm_channels = 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;
}

static void write_pcm_s32(struct amdtp_stream *s, struct snd_pcm_substream *pcm,
                          __be32 *buffer, unsigned int frames)
{
        struct amdtp_dot *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;

        buffer++;
        for (i = 0; i < frames; ++i) {
                for (c = 0; c < channels; ++c) {
                        buffer[c] = cpu_to_be32((*src >> 8) | 0x40000000);
                        dot_encode_step(&p->state, &buffer[c]);
                        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_dot *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;

        buffer++;
        for (i = 0; i < frames; ++i) {
                for (c = 0; c < channels; ++c) {
                        *dst = be32_to_cpu(buffer[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 data_blocks)
{
        struct amdtp_dot *p = s->protocol;
        unsigned int channels, i, c;

        channels = p->pcm_channels;

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

static bool midi_ratelimit_per_packet(struct amdtp_stream *s, unsigned int port)
{
        struct amdtp_dot *p = s->protocol;
        int used;

        used = p->midi_fifo_used[port];
        if (used == 0)
                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 inline void midi_use_bytes(struct amdtp_stream *s,
                                  unsigned int port, unsigned int count)
{
        struct amdtp_dot *p = s->protocol;

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

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

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

                len = 0;
                if (port < MAX_MIDI_PORTS &&
                    midi_ratelimit_per_packet(s, port) &&
                    p->midi[port] != NULL)
                        len = snd_rawmidi_transmit(p->midi[port], b + 1, 2);

                if (len > 0) {
                        /*
                         * Upper 4 bits of LSB represent port number.
                         * - 0000b: physical MIDI port 1.
                         * - 0010b: physical MIDI port 2.
                         * - 1110b: console MIDI port.
                         */
                        if (port == 2)
                                b[3] = 0xe0;
                        else if (port == 1)
                                b[3] = 0x20;
                        else
                                b[3] = 0x00;
                        b[3] |= len;
                        midi_use_bytes(s, port, len);
                } else {
                        b[1] = 0;
                        b[2] = 0;
                        b[3] = 0;
                }
                b[0] = 0x80;

                buffer += s->data_block_quadlets;
        }
}

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

        for (f = 0; f < data_blocks; f++) {
                b = (u8 *)&buffer[0];

                len = b[3] & 0x0f;
                if (len > 0) {
                        /*
                         * Upper 4 bits of LSB represent port number.
                         * - 0000b: physical MIDI port 1. Use port 0.
                         * - 1110b: console MIDI port. Use port 2.
                         */
                        if (b[3] >> 4 > 0)
                                port = 2;
                        else
                                port = 0;

                        if (port < MAX_MIDI_PORTS && p->midi[port])
                                snd_rawmidi_receive(p->midi[port], b + 1, len);
                }

                buffer += s->data_block_quadlets;
        }
}

int amdtp_dot_add_pcm_hw_constraints(struct amdtp_stream *s,
                                     struct snd_pcm_runtime *runtime)
{
        int err;

        /* This protocol delivers 24 bit data in 32bit data channel. */
        err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
        if (err < 0)
                return err;

        return amdtp_stream_add_pcm_hw_constraints(s, runtime);
}

void amdtp_dot_midi_trigger(struct amdtp_stream *s, unsigned int port,
                          struct snd_rawmidi_substream *midi)
{
        struct amdtp_dot *p = s->protocol;

        if (port < MAX_MIDI_PORTS)
                WRITE_ONCE(p->midi[port], midi);
}

static unsigned int process_tx_data_blocks(struct amdtp_stream *s,
                                           __be32 *buffer,
                                           unsigned int data_blocks,
                                           unsigned int *syt)
{
        struct snd_pcm_substream *pcm;
        unsigned int pcm_frames;

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

        read_midi_messages(s, buffer, data_blocks);

        return pcm_frames;
}

static unsigned int process_rx_data_blocks(struct amdtp_stream *s,
                                           __be32 *buffer,
                                           unsigned int data_blocks,
                                           unsigned int *syt)
{
        struct snd_pcm_substream *pcm;
        unsigned int pcm_frames;

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

        write_midi_messages(s, buffer, data_blocks);

        return pcm_frames;
}

int amdtp_dot_init(struct amdtp_stream *s, struct fw_unit *unit,
                 enum amdtp_stream_direction dir)
{
        amdtp_stream_process_data_blocks_t process_data_blocks;
        enum cip_flags flags;

        /* Use different mode between incoming/outgoing. */
        if (dir == AMDTP_IN_STREAM) {
                flags = CIP_NONBLOCKING;
                process_data_blocks = process_tx_data_blocks;
        } else {
                flags = CIP_BLOCKING;
                process_data_blocks = process_rx_data_blocks;
        }

        return amdtp_stream_init(s, unit, dir, flags, CIP_FMT_AM,
                                 process_data_blocks, sizeof(struct amdtp_dot));
}

void amdtp_dot_reset(struct amdtp_stream *s)
{
        struct amdtp_dot *p = s->protocol;

        p->state.carry = 0x00;
        p->state.idx = 0x00;
        p->state.off = 0;
}