ALSA: firewire-tascam: add data block processing layer

TASCAM FireWire series uses non-blocking transmission for AMDTP packet
streaming, while the format of data blocks is unique.

The CIP headers includes specific value in FMT field and no SYT
information.

In transmitted packets, the first data channel represents event counter,
and the last data channel has status and control information. The rest
has 24bit PCM samples with right padding.

In received packets, all of data channels include 16, 24, 32bit PCM
samples. There's no other kind of information.

This commit adds support for this protocol. For convenience, the size of
PCM samples in outgoing packet is limited by 16 and 24bit. The status and
control information will be supported in future commits.

Signed-off-by: Takashi Sakamoto <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/firewire/tascam/Makefile

···
-snd-firewire-tascam-objs := tascam-proc.o tascam.o
+snd-firewire-tascam-objs := tascam-proc.o amdtp-tascam.o tascam.o
 obj-$(CONFIG_SND_FIREWIRE_TASCAM) += snd-firewire-tascam.o

sound/firewire/tascam/amdtp-tascam.c

···
+/*
+ * amdtp-tascam.c - a part of driver for TASCAM FireWire series
+ *
+ * Copyright (c) 2015 Takashi Sakamoto
+ *
+ * Licensed under the terms of the GNU General Public License, version 2.
+ */
+
+#include <sound/pcm.h>
+#include "tascam.h"
+
+#define AMDTP_FMT_TSCM_TX	0x1e
+#define AMDTP_FMT_TSCM_RX	0x3e
+
+struct amdtp_tscm {
+	unsigned int pcm_channels;
+
+	void (*transfer_samples)(struct amdtp_stream *s,
+				 struct snd_pcm_substream *pcm,
+				 __be32 *buffer, unsigned int frames);
+};
+
+int amdtp_tscm_set_parameters(struct amdtp_stream *s, unsigned int rate)
+{
+	struct amdtp_tscm *p = s->protocol;
+	unsigned int data_channels;
+
+	if (amdtp_stream_running(s))
+		return -EBUSY;
+
+	data_channels = p->pcm_channels;
+
+	/* Packets in in-stream have extra 2 data channels. */
+	if (s->direction == AMDTP_IN_STREAM)
+		data_channels += 2;
+
+	return amdtp_stream_set_parameters(s, rate, data_channels);
+}
+
+static void write_pcm_s32(struct amdtp_stream *s,
+			  struct snd_pcm_substream *pcm,
+			  __be32 *buffer, unsigned int frames)
+{
+	struct amdtp_tscm *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[c] = cpu_to_be32(*src);
+			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_tscm *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[c] = cpu_to_be32(*src << 16);
+			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_tscm *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;
+
+	/* The first data channel is for event counter. */
+	buffer += 1;
+
+	for (i = 0; i < frames; ++i) {
+		for (c = 0; c < channels; ++c) {
+			*dst = be32_to_cpu(buffer[c]);
+			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_tscm *p = s->protocol;
+	unsigned int channels, i, c;
+
+	channels = p->pcm_channels;
+
+	for (i = 0; i < data_blocks; ++i) {
+		for (c = 0; c < channels; ++c)
+			buffer[c] = 0x00000000;
+		buffer += s->data_block_quadlets;
+	}
+}
+
+int amdtp_tscm_add_pcm_hw_constraints(struct amdtp_stream *s,
+				      struct snd_pcm_runtime *runtime)
+{
+	int err;
+
+	/*
+	 * Our implementation allows this protocol to deliver 24 bit sample 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_tscm_set_pcm_format(struct amdtp_stream *s, snd_pcm_format_t format)
+{
+	struct amdtp_tscm *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;
+	}
+}
+
+static unsigned int process_tx_data_blocks(struct amdtp_stream *s,
+					   __be32 *buffer,
+					   unsigned int data_blocks,
+					   unsigned int *syt)
+{
+	struct amdtp_tscm *p = (struct amdtp_tscm *)s->protocol;
+	struct snd_pcm_substream *pcm;
+
+	pcm = ACCESS_ONCE(s->pcm);
+	if (data_blocks > 0 && pcm)
+		p->transfer_samples(s, pcm, buffer, data_blocks);
+
+	/* A place holder for control messages. */
+
+	return data_blocks;
+}
+
+static unsigned int process_rx_data_blocks(struct amdtp_stream *s,
+					   __be32 *buffer,
+					   unsigned int data_blocks,
+					   unsigned int *syt)
+{
+	struct amdtp_tscm *p = (struct amdtp_tscm *)s->protocol;
+	struct snd_pcm_substream *pcm;
+
+	/* This field is not used. */
+	*syt = 0x0000;
+
+	pcm = ACCESS_ONCE(s->pcm);
+	if (pcm)
+		p->transfer_samples(s, pcm, buffer, data_blocks);
+	else
+		write_pcm_silence(s, buffer, data_blocks);
+
+	return data_blocks;
+}
+
+int amdtp_tscm_init(struct amdtp_stream *s, struct fw_unit *unit,
+		    enum amdtp_stream_direction dir, unsigned int pcm_channels)
+{
+	amdtp_stream_process_data_blocks_t process_data_blocks;
+	struct amdtp_tscm *p;
+	unsigned int fmt;
+	int err;
+
+	if (dir == AMDTP_IN_STREAM) {
+		fmt = AMDTP_FMT_TSCM_TX;
+		process_data_blocks = process_tx_data_blocks;
+	} else {
+		fmt = AMDTP_FMT_TSCM_RX;
+		process_data_blocks = process_rx_data_blocks;
+	}
+
+	err = amdtp_stream_init(s, unit, dir,
+				CIP_NONBLOCKING | CIP_SKIP_DBC_ZERO_CHECK, fmt,
+				process_data_blocks, sizeof(struct amdtp_tscm));
+	if (err < 0)
+		return 0;
+
+	/* Use fixed value for FDF field. */
+	s->fdf = 0x00;
+
+	/* This protocol uses fixed number of data channels for PCM samples. */
+	p = s->protocol;
+	p->pcm_channels = pcm_channels;
+
+	return 0;
+}

sound/firewire/tascam/tascam.h

···
 #include <sound/core.h>
 #include <sound/initval.h>
 #include <sound/info.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
 
 #include "../lib.h"
+#include "../amdtp-stream.h"
 
 struct snd_tscm_spec {
 	const char *const name;
···
 #define TSCM_OFFSET_FIRMWARE_FPGA	0x0004
 #define TSCM_OFFSET_FIRMWARE_ARM	0x0008
 #define TSCM_OFFSET_FIRMWARE_HW		0x000c
+
+int amdtp_tscm_init(struct amdtp_stream *s, struct fw_unit *unit,
+		  enum amdtp_stream_direction dir, unsigned int pcm_channels);
+int amdtp_tscm_set_parameters(struct amdtp_stream *s, unsigned int rate);
+int amdtp_tscm_add_pcm_hw_constraints(struct amdtp_stream *s,
+				      struct snd_pcm_runtime *runtime);
+void amdtp_tscm_set_pcm_format(struct amdtp_stream *s, snd_pcm_format_t format);
 
 void snd_tscm_proc_init(struct snd_tscm *tscm);