1 // SPDX-License-Identifier: GPL-2.0-only
3 * AM824 format in Audio and Music Data Transmission Protocol (IEC 61883-6)
5 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
6 * Copyright (c) 2015 Takashi Sakamoto <o-takashi@sakamocchi.jp>
9 #include <linux/slab.h>
11 #include "amdtp-am824.h"
13 #define CIP_FMT_AM 0x10
15 /* "Clock-based rate control mode" is just supported. */
16 #define AMDTP_FDF_AM824 0x00
19 * Nominally 3125 bytes/second, but the MIDI port's clock might be
20 * 1% too slow, and the bus clock 100 ppm too fast.
22 #define MIDI_BYTES_PER_SECOND 3093
25 * Several devices look only at the first eight data blocks.
26 * In any case, this is more than enough for the MIDI data rate.
28 #define MAX_MIDI_RX_BLOCKS 8
31 struct snd_rawmidi_substream *midi[AM824_MAX_CHANNELS_FOR_MIDI * 8];
33 int midi_fifo_used[AM824_MAX_CHANNELS_FOR_MIDI * 8];
34 unsigned int pcm_channels;
35 unsigned int midi_ports;
37 u8 pcm_positions[AM824_MAX_CHANNELS_FOR_PCM];
40 unsigned int frame_multiplier;
44 * amdtp_am824_set_parameters - set stream parameters
45 * @s: the AMDTP stream to configure
46 * @rate: the sample rate
47 * @pcm_channels: the number of PCM samples in each data block, to be encoded
48 * as AM824 multi-bit linear audio
49 * @midi_ports: the number of MIDI ports (i.e., MPX-MIDI Data Channels)
50 * @double_pcm_frames: one data block transfers two PCM frames
52 * The parameters must be set before the stream is started, and must not be
53 * changed while the stream is running.
55 int amdtp_am824_set_parameters(struct amdtp_stream *s, unsigned int rate,
56 unsigned int pcm_channels,
57 unsigned int midi_ports,
58 bool double_pcm_frames)
60 struct amdtp_am824 *p = s->protocol;
61 unsigned int midi_channels;
65 if (amdtp_stream_running(s))
68 if (pcm_channels > AM824_MAX_CHANNELS_FOR_PCM)
71 midi_channels = DIV_ROUND_UP(midi_ports, 8);
72 if (midi_channels > AM824_MAX_CHANNELS_FOR_MIDI)
75 if (WARN_ON(amdtp_stream_running(s)) ||
76 WARN_ON(pcm_channels > AM824_MAX_CHANNELS_FOR_PCM) ||
77 WARN_ON(midi_channels > AM824_MAX_CHANNELS_FOR_MIDI))
80 err = amdtp_stream_set_parameters(s, rate,
81 pcm_channels + midi_channels);
85 s->ctx_data.rx.fdf = AMDTP_FDF_AM824 | s->sfc;
87 p->pcm_channels = pcm_channels;
88 p->midi_ports = midi_ports;
91 * In IEC 61883-6, one data block represents one event. In ALSA, one
92 * event equals to one PCM frame. But Dice has a quirk at higher
93 * sampling rate to transfer two PCM frames in one data block.
95 if (double_pcm_frames)
96 p->frame_multiplier = 2;
98 p->frame_multiplier = 1;
100 /* init the position map for PCM and MIDI channels */
101 for (i = 0; i < pcm_channels; i++)
102 p->pcm_positions[i] = i;
103 p->midi_position = p->pcm_channels;
106 * We do not know the actual MIDI FIFO size of most devices. Just
107 * assume two bytes, i.e., one byte can be received over the bus while
108 * the previous one is transmitted over MIDI.
109 * (The value here is adjusted for midi_ratelimit_per_packet().)
111 p->midi_fifo_limit = rate - MIDI_BYTES_PER_SECOND * s->syt_interval + 1;
115 EXPORT_SYMBOL_GPL(amdtp_am824_set_parameters);
118 * amdtp_am824_set_pcm_position - set an index of data channel for a channel
120 * @s: the AMDTP stream
121 * @index: the index of data channel in an data block
122 * @position: the channel of PCM frame
124 void amdtp_am824_set_pcm_position(struct amdtp_stream *s, unsigned int index,
125 unsigned int position)
127 struct amdtp_am824 *p = s->protocol;
129 if (index < p->pcm_channels)
130 p->pcm_positions[index] = position;
132 EXPORT_SYMBOL_GPL(amdtp_am824_set_pcm_position);
135 * amdtp_am824_set_midi_position - set a index of data channel for MIDI
136 * conformant data channel
137 * @s: the AMDTP stream
138 * @position: the index of data channel in an data block
140 void amdtp_am824_set_midi_position(struct amdtp_stream *s,
141 unsigned int position)
143 struct amdtp_am824 *p = s->protocol;
145 p->midi_position = position;
147 EXPORT_SYMBOL_GPL(amdtp_am824_set_midi_position);
149 static void write_pcm_s32(struct amdtp_stream *s,
150 struct snd_pcm_substream *pcm,
151 __be32 *buffer, unsigned int frames)
153 struct amdtp_am824 *p = s->protocol;
154 struct snd_pcm_runtime *runtime = pcm->runtime;
155 unsigned int channels, remaining_frames, i, c;
158 channels = p->pcm_channels;
159 src = (void *)runtime->dma_area +
160 frames_to_bytes(runtime, s->pcm_buffer_pointer);
161 remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
163 for (i = 0; i < frames; ++i) {
164 for (c = 0; c < channels; ++c) {
165 buffer[p->pcm_positions[c]] =
166 cpu_to_be32((*src >> 8) | 0x40000000);
169 buffer += s->data_block_quadlets;
170 if (--remaining_frames == 0)
171 src = (void *)runtime->dma_area;
175 static void read_pcm_s32(struct amdtp_stream *s,
176 struct snd_pcm_substream *pcm,
177 __be32 *buffer, unsigned int frames)
179 struct amdtp_am824 *p = s->protocol;
180 struct snd_pcm_runtime *runtime = pcm->runtime;
181 unsigned int channels, remaining_frames, i, c;
184 channels = p->pcm_channels;
185 dst = (void *)runtime->dma_area +
186 frames_to_bytes(runtime, s->pcm_buffer_pointer);
187 remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
189 for (i = 0; i < frames; ++i) {
190 for (c = 0; c < channels; ++c) {
191 *dst = be32_to_cpu(buffer[p->pcm_positions[c]]) << 8;
194 buffer += s->data_block_quadlets;
195 if (--remaining_frames == 0)
196 dst = (void *)runtime->dma_area;
200 static void write_pcm_silence(struct amdtp_stream *s,
201 __be32 *buffer, unsigned int frames)
203 struct amdtp_am824 *p = s->protocol;
204 unsigned int i, c, channels = p->pcm_channels;
206 for (i = 0; i < frames; ++i) {
207 for (c = 0; c < channels; ++c)
208 buffer[p->pcm_positions[c]] = cpu_to_be32(0x40000000);
209 buffer += s->data_block_quadlets;
214 * amdtp_am824_add_pcm_hw_constraints - add hw constraints for PCM substream
215 * @s: the AMDTP stream for AM824 data block, must be initialized.
216 * @runtime: the PCM substream runtime
219 int amdtp_am824_add_pcm_hw_constraints(struct amdtp_stream *s,
220 struct snd_pcm_runtime *runtime)
224 err = amdtp_stream_add_pcm_hw_constraints(s, runtime);
228 /* AM824 in IEC 61883-6 can deliver 24bit data. */
229 return snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
231 EXPORT_SYMBOL_GPL(amdtp_am824_add_pcm_hw_constraints);
234 * amdtp_am824_midi_trigger - start/stop playback/capture with a MIDI device
235 * @s: the AMDTP stream
236 * @port: index of MIDI port
237 * @midi: the MIDI device to be started, or %NULL to stop the current device
239 * Call this function on a running isochronous stream to enable the actual
240 * transmission of MIDI data. This function should be called from the MIDI
241 * device's .trigger callback.
243 void amdtp_am824_midi_trigger(struct amdtp_stream *s, unsigned int port,
244 struct snd_rawmidi_substream *midi)
246 struct amdtp_am824 *p = s->protocol;
248 if (port < p->midi_ports)
249 WRITE_ONCE(p->midi[port], midi);
251 EXPORT_SYMBOL_GPL(amdtp_am824_midi_trigger);
254 * To avoid sending MIDI bytes at too high a rate, assume that the receiving
255 * device has a FIFO, and track how much it is filled. This values increases
256 * by one whenever we send one byte in a packet, but the FIFO empties at
257 * a constant rate independent of our packet rate. One packet has syt_interval
258 * samples, so the number of bytes that empty out of the FIFO, per packet(!),
259 * is MIDI_BYTES_PER_SECOND * syt_interval / sample_rate. To avoid storing
260 * fractional values, the values in midi_fifo_used[] are measured in bytes
261 * multiplied by the sample rate.
263 static bool midi_ratelimit_per_packet(struct amdtp_stream *s, unsigned int port)
265 struct amdtp_am824 *p = s->protocol;
268 used = p->midi_fifo_used[port];
269 if (used == 0) /* common shortcut */
272 used -= MIDI_BYTES_PER_SECOND * s->syt_interval;
274 p->midi_fifo_used[port] = used;
276 return used < p->midi_fifo_limit;
279 static void midi_rate_use_one_byte(struct amdtp_stream *s, unsigned int port)
281 struct amdtp_am824 *p = s->protocol;
283 p->midi_fifo_used[port] += amdtp_rate_table[s->sfc];
286 static void write_midi_messages(struct amdtp_stream *s, __be32 *buffer,
289 struct amdtp_am824 *p = s->protocol;
290 unsigned int f, port;
293 for (f = 0; f < frames; f++) {
294 b = (u8 *)&buffer[p->midi_position];
296 port = (s->data_block_counter + f) % 8;
297 if (f < MAX_MIDI_RX_BLOCKS &&
298 midi_ratelimit_per_packet(s, port) &&
299 p->midi[port] != NULL &&
300 snd_rawmidi_transmit(p->midi[port], &b[1], 1) == 1) {
301 midi_rate_use_one_byte(s, port);
310 buffer += s->data_block_quadlets;
314 static void read_midi_messages(struct amdtp_stream *s,
315 __be32 *buffer, unsigned int frames)
317 struct amdtp_am824 *p = s->protocol;
318 unsigned int f, port;
322 for (f = 0; f < frames; f++) {
323 port = (8 - s->ctx_data.tx.first_dbc + s->data_block_counter + f) % 8;
324 b = (u8 *)&buffer[p->midi_position];
327 if ((1 <= len) && (len <= 3) && (p->midi[port]))
328 snd_rawmidi_receive(p->midi[port], b + 1, len);
330 buffer += s->data_block_quadlets;
334 static unsigned int process_rx_data_blocks(struct amdtp_stream *s, __be32 *buffer,
335 unsigned int data_blocks, unsigned int *syt)
337 struct amdtp_am824 *p = s->protocol;
338 struct snd_pcm_substream *pcm = READ_ONCE(s->pcm);
339 unsigned int pcm_frames;
342 write_pcm_s32(s, pcm, buffer, data_blocks);
343 pcm_frames = data_blocks * p->frame_multiplier;
345 write_pcm_silence(s, buffer, data_blocks);
350 write_midi_messages(s, buffer, data_blocks);
355 static unsigned int process_tx_data_blocks(struct amdtp_stream *s, __be32 *buffer,
356 unsigned int data_blocks, unsigned int *syt)
358 struct amdtp_am824 *p = s->protocol;
359 struct snd_pcm_substream *pcm = READ_ONCE(s->pcm);
360 unsigned int pcm_frames;
363 read_pcm_s32(s, pcm, buffer, data_blocks);
364 pcm_frames = data_blocks * p->frame_multiplier;
370 read_midi_messages(s, buffer, data_blocks);
376 * amdtp_am824_init - initialize an AMDTP stream structure to handle AM824
378 * @s: the AMDTP stream to initialize
379 * @unit: the target of the stream
380 * @dir: the direction of stream
381 * @flags: the packet transmission method to use
383 int amdtp_am824_init(struct amdtp_stream *s, struct fw_unit *unit,
384 enum amdtp_stream_direction dir, enum cip_flags flags)
386 amdtp_stream_process_data_blocks_t process_data_blocks;
388 if (dir == AMDTP_IN_STREAM)
389 process_data_blocks = process_tx_data_blocks;
391 process_data_blocks = process_rx_data_blocks;
393 return amdtp_stream_init(s, unit, dir, flags, CIP_FMT_AM,
395 sizeof(struct amdtp_am824));
397 EXPORT_SYMBOL_GPL(amdtp_am824_init);