/*
   * 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>
   *
   * Licensed under the terms of the GNU General Public License, version 2.
   */
  
  #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
  
  /*
   * 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;
  
  	unsigned int midi_ports;
  	/* 2 = MAX(DOT_MIDI_IN_PORTS, DOT_MIDI_OUT_PORTS) */
  	struct snd_rawmidi_substream *midi[2];
  	int midi_fifo_used[2];
  	int midi_fifo_limit;
  
  	void (*transfer_samples)(struct amdtp_stream *s,
  				 struct snd_pcm_substream *pcm,
  				 __be32 *buffer, unsigned int frames);
  };
  
  /*
   * 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 const 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 conformant data channel, 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->fdf = AMDTP_FDF_AM824 | s->sfc;
  
  	p->pcm_channels = pcm_channels;
  
  	if (s->direction == AMDTP_IN_STREAM)
  		p->midi_ports = DOT_MIDI_IN_PORTS;
  	else
  		p->midi_ports = DOT_MIDI_OUT_PORTS;
  
  	/*
  	 * 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 write_pcm_s16(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 u16 *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 < p->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) {
  			b[3] = (0x10 << port) | 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];
  		port = b[3] >> 4;
  		len = b[3] & 0x0f;
  
  		if (port < p->midi_ports && p->midi[port] && len > 0)
  			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_set_pcm_format(struct amdtp_stream *s, snd_pcm_format_t format)
  {
  	struct amdtp_dot *p = s->protocol;
  
  	if (WARN_ON(amdtp_stream_pcm_running(s)))
  		return;
  
  	switch (format) {
  	default:
  		WARN_ON(1);
  		/* fall through */
  	case SNDRV_PCM_FORMAT_S16:
  		if (s->direction == AMDTP_OUT_STREAM) {
  			p->transfer_samples = write_pcm_s16;
  			break;
  		}
  		WARN_ON(1);
  		/* fall through */
  	case SNDRV_PCM_FORMAT_S32:
  		if (s->direction == AMDTP_OUT_STREAM)
  			p->transfer_samples = write_pcm_s32;
  		else
  			p->transfer_samples = read_pcm_s32;
  		break;
  	}
  }
  
  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 < p->midi_ports)
  		ACCESS_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 amdtp_dot *p = (struct amdtp_dot *)s->protocol;
  	struct snd_pcm_substream *pcm;
  	unsigned int pcm_frames;
  
  	pcm = ACCESS_ONCE(s->pcm);
  	if (pcm) {
  		p->transfer_samples(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 amdtp_dot *p = (struct amdtp_dot *)s->protocol;
  	struct snd_pcm_substream *pcm;
  	unsigned int pcm_frames;
  
  	pcm = ACCESS_ONCE(s->pcm);
  	if (pcm) {
  		p->transfer_samples(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 | CIP_SKIP_INIT_DBC_CHECK;
  		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;
  }