/*
   * 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;
  
  	void (*transfer_samples)(struct amdtp_stream *s,
  				 struct snd_pcm_substream *pcm,
  				 __be32 *buffer, unsigned int frames);
  
  	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 write_pcm_s16(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 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;
  
  	for (i = 0; i < frames; ++i) {
  		for (c = 0; c < channels; ++c) {
  			buffer[p->pcm_positions[c]] =
  					cpu_to_be32((*src << 8) | 0x42000000);
  			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_set_pcm_format - set the PCM format
   * @s: the AMDTP stream to configure
   * @format: the format of the ALSA PCM device
   *
   * The sample format must be set after the other parameters (rate/PCM channels/
   * MIDI) and before the stream is started, and must not be changed while the
   * stream is running.
   */
  void amdtp_am824_set_pcm_format(struct amdtp_stream *s, snd_pcm_format_t format)
  {
  	struct amdtp_am824 *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;
  	}
  }
  EXPORT_SYMBOL_GPL(amdtp_am824_set_pcm_format);
  
  /**
   * 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) {
  		p->transfer_samples(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) {
  		p->transfer_samples(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);