1 // SPDX-License-Identifier: GPL-2.0-only
3 * amdtp-dot.c - a part of driver for Digidesign Digi 002/003 family
5 * Copyright (c) 2014-2015 Takashi Sakamoto
6 * Copyright (C) 2012 Robin Gareus <robin@gareus.org>
7 * Copyright (C) 2012 Damien Zammit <damien@zamaudio.com>
10 #include <sound/pcm.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
30 /* 3 = MAX(DOT_MIDI_IN_PORTS, DOT_MIDI_OUT_PORTS) + 1. */
31 #define MAX_MIDI_PORTS 3
34 * The double-oh-three algorithm was discovered by Robin Gareus and Damien
35 * Zammit in 2012, with reverse-engineering for Digi 003 Rack.
44 unsigned int pcm_channels;
45 struct dot_state state;
47 struct snd_rawmidi_substream *midi[MAX_MIDI_PORTS];
48 int midi_fifo_used[MAX_MIDI_PORTS];
53 * double-oh-three look up table
55 * @param idx index byte (audio-sample data) 0x00..0xff
56 * @param off channel offset shift
57 * @return salt to XOR with given data
59 #define BYTE_PER_SAMPLE (4)
60 #define MAGIC_DOT_BYTE (2)
61 #define MAGIC_BYTE_OFF(x) (((x) * BYTE_PER_SAMPLE) + MAGIC_DOT_BYTE)
62 static u8 dot_scrt(const u8 idx, const unsigned int off)
65 * the length of the added pattern only depends on the lower nibble
66 * of the last non-zero data
68 static const u8 len[16] = {0, 1, 3, 5, 7, 9, 11, 13, 14,
69 12, 10, 8, 6, 4, 2, 0};
72 * the lower nibble of the salt. Interleaved sequence.
73 * this is walked backwards according to len[]
75 static const u8 nib[15] = {0x8, 0x7, 0x9, 0x6, 0xa, 0x5, 0xb, 0x4,
76 0xc, 0x3, 0xd, 0x2, 0xe, 0x1, 0xf};
78 /* circular list for the salt's hi nibble. */
79 static const u8 hir[15] = {0x0, 0x6, 0xf, 0x8, 0x7, 0x5, 0x3, 0x4,
80 0xc, 0xd, 0xe, 0x1, 0x2, 0xb, 0xa};
83 * start offset for upper nibble mapping.
84 * note: 9 is /special/. In the case where the high nibble == 0x9,
85 * hir[] is not used and - coincidentally - the salt's hi nibble is
86 * 0x09 regardless of the offset.
88 static const u8 hio[16] = {0, 11, 12, 6, 7, 5, 1, 4,
89 3, 0x00, 14, 13, 8, 9, 10, 2};
91 const u8 ln = idx & 0xf;
92 const u8 hn = (idx >> 4) & 0xf;
93 const u8 hr = (hn == 0x9) ? 0x9 : hir[(hio[hn] + off) % 15];
98 return ((nib[14 + off - len[ln]]) | (hr << 4));
101 static void dot_encode_step(struct dot_state *state, __be32 *const buffer)
103 u8 * const data = (u8 *) buffer;
105 if (data[MAGIC_DOT_BYTE] != 0x00) {
107 state->idx = data[MAGIC_DOT_BYTE] ^ state->carry;
109 data[MAGIC_DOT_BYTE] ^= state->carry;
110 state->carry = dot_scrt(state->idx, ++(state->off));
113 int amdtp_dot_set_parameters(struct amdtp_stream *s, unsigned int rate,
114 unsigned int pcm_channels)
116 struct amdtp_dot *p = s->protocol;
119 if (amdtp_stream_running(s))
123 * A first data channel is for MIDI messages, the rest is Multi Bit
124 * Linear Audio data channel.
126 err = amdtp_stream_set_parameters(s, rate, pcm_channels + 1);
130 s->fdf = AMDTP_FDF_AM824 | s->sfc;
132 p->pcm_channels = pcm_channels;
135 * We do not know the actual MIDI FIFO size of most devices. Just
136 * assume two bytes, i.e., one byte can be received over the bus while
137 * the previous one is transmitted over MIDI.
138 * (The value here is adjusted for midi_ratelimit_per_packet().)
140 p->midi_fifo_limit = rate - MIDI_BYTES_PER_SECOND * s->syt_interval + 1;
145 static void write_pcm_s32(struct amdtp_stream *s, struct snd_pcm_substream *pcm,
146 __be32 *buffer, unsigned int frames)
148 struct amdtp_dot *p = s->protocol;
149 struct snd_pcm_runtime *runtime = pcm->runtime;
150 unsigned int channels, remaining_frames, i, c;
153 channels = p->pcm_channels;
154 src = (void *)runtime->dma_area +
155 frames_to_bytes(runtime, s->pcm_buffer_pointer);
156 remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
159 for (i = 0; i < frames; ++i) {
160 for (c = 0; c < channels; ++c) {
161 buffer[c] = cpu_to_be32((*src >> 8) | 0x40000000);
162 dot_encode_step(&p->state, &buffer[c]);
165 buffer += s->data_block_quadlets;
166 if (--remaining_frames == 0)
167 src = (void *)runtime->dma_area;
171 static void read_pcm_s32(struct amdtp_stream *s, struct snd_pcm_substream *pcm,
172 __be32 *buffer, unsigned int frames)
174 struct amdtp_dot *p = s->protocol;
175 struct snd_pcm_runtime *runtime = pcm->runtime;
176 unsigned int channels, remaining_frames, i, c;
179 channels = p->pcm_channels;
180 dst = (void *)runtime->dma_area +
181 frames_to_bytes(runtime, s->pcm_buffer_pointer);
182 remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
185 for (i = 0; i < frames; ++i) {
186 for (c = 0; c < channels; ++c) {
187 *dst = be32_to_cpu(buffer[c]) << 8;
190 buffer += s->data_block_quadlets;
191 if (--remaining_frames == 0)
192 dst = (void *)runtime->dma_area;
196 static void write_pcm_silence(struct amdtp_stream *s, __be32 *buffer,
197 unsigned int data_blocks)
199 struct amdtp_dot *p = s->protocol;
200 unsigned int channels, i, c;
202 channels = p->pcm_channels;
205 for (i = 0; i < data_blocks; ++i) {
206 for (c = 0; c < channels; ++c)
207 buffer[c] = cpu_to_be32(0x40000000);
208 buffer += s->data_block_quadlets;
212 static bool midi_ratelimit_per_packet(struct amdtp_stream *s, unsigned int port)
214 struct amdtp_dot *p = s->protocol;
217 used = p->midi_fifo_used[port];
221 used -= MIDI_BYTES_PER_SECOND * s->syt_interval;
223 p->midi_fifo_used[port] = used;
225 return used < p->midi_fifo_limit;
228 static inline void midi_use_bytes(struct amdtp_stream *s,
229 unsigned int port, unsigned int count)
231 struct amdtp_dot *p = s->protocol;
233 p->midi_fifo_used[port] += amdtp_rate_table[s->sfc] * count;
236 static void write_midi_messages(struct amdtp_stream *s, __be32 *buffer,
237 unsigned int data_blocks)
239 struct amdtp_dot *p = s->protocol;
240 unsigned int f, port;
244 for (f = 0; f < data_blocks; f++) {
245 port = (s->data_block_counter + f) % 8;
246 b = (u8 *)&buffer[0];
249 if (port < MAX_MIDI_PORTS &&
250 midi_ratelimit_per_packet(s, port) &&
251 p->midi[port] != NULL)
252 len = snd_rawmidi_transmit(p->midi[port], b + 1, 2);
256 * Upper 4 bits of LSB represent port number.
257 * - 0000b: physical MIDI port 1.
258 * - 0010b: physical MIDI port 2.
259 * - 1110b: console MIDI port.
268 midi_use_bytes(s, port, len);
276 buffer += s->data_block_quadlets;
280 static void read_midi_messages(struct amdtp_stream *s, __be32 *buffer,
281 unsigned int data_blocks)
283 struct amdtp_dot *p = s->protocol;
284 unsigned int f, port, len;
287 for (f = 0; f < data_blocks; f++) {
288 b = (u8 *)&buffer[0];
293 * Upper 4 bits of LSB represent port number.
294 * - 0000b: physical MIDI port 1. Use port 0.
295 * - 1110b: console MIDI port. Use port 2.
302 if (port < MAX_MIDI_PORTS && p->midi[port])
303 snd_rawmidi_receive(p->midi[port], b + 1, len);
306 buffer += s->data_block_quadlets;
310 int amdtp_dot_add_pcm_hw_constraints(struct amdtp_stream *s,
311 struct snd_pcm_runtime *runtime)
315 /* This protocol delivers 24 bit data in 32bit data channel. */
316 err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
320 return amdtp_stream_add_pcm_hw_constraints(s, runtime);
323 void amdtp_dot_midi_trigger(struct amdtp_stream *s, unsigned int port,
324 struct snd_rawmidi_substream *midi)
326 struct amdtp_dot *p = s->protocol;
328 if (port < MAX_MIDI_PORTS)
329 WRITE_ONCE(p->midi[port], midi);
332 static unsigned int process_tx_data_blocks(struct amdtp_stream *s,
334 unsigned int data_blocks,
337 struct snd_pcm_substream *pcm;
338 unsigned int pcm_frames;
340 pcm = READ_ONCE(s->pcm);
342 read_pcm_s32(s, pcm, buffer, data_blocks);
343 pcm_frames = data_blocks;
348 read_midi_messages(s, buffer, data_blocks);
353 static unsigned int process_rx_data_blocks(struct amdtp_stream *s,
355 unsigned int data_blocks,
358 struct snd_pcm_substream *pcm;
359 unsigned int pcm_frames;
361 pcm = READ_ONCE(s->pcm);
363 write_pcm_s32(s, pcm, buffer, data_blocks);
364 pcm_frames = data_blocks;
366 write_pcm_silence(s, buffer, data_blocks);
370 write_midi_messages(s, buffer, data_blocks);
375 int amdtp_dot_init(struct amdtp_stream *s, struct fw_unit *unit,
376 enum amdtp_stream_direction dir)
378 amdtp_stream_process_data_blocks_t process_data_blocks;
379 enum cip_flags flags;
381 /* Use different mode between incoming/outgoing. */
382 if (dir == AMDTP_IN_STREAM) {
383 flags = CIP_NONBLOCKING;
384 process_data_blocks = process_tx_data_blocks;
386 flags = CIP_BLOCKING;
387 process_data_blocks = process_rx_data_blocks;
390 return amdtp_stream_init(s, unit, dir, flags, CIP_FMT_AM,
391 process_data_blocks, sizeof(struct amdtp_dot));
394 void amdtp_dot_reset(struct amdtp_stream *s)
396 struct amdtp_dot *p = s->protocol;
398 p->state.carry = 0x00;