1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * amdtp-dot.c - a part of driver for Digidesign Digi 002/003 family
4 *
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>
8 */
9
10#include <sound/pcm.h>
11#include "digi00x.h"
12
13#define CIP_FMT_AM		0x10
14
15/* 'Clock-based rate control mode' is just supported. */
16#define AMDTP_FDF_AM824		0x00
17
18/*
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.
21 */
22#define MIDI_BYTES_PER_SECOND	3093
23
24/*
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.
27 */
28#define MAX_MIDI_RX_BLOCKS	8
29
30/* 3 = MAX(DOT_MIDI_IN_PORTS, DOT_MIDI_OUT_PORTS) + 1. */
31#define MAX_MIDI_PORTS		3
32
33/*
34 * The double-oh-three algorithm was discovered by Robin Gareus and Damien
35 * Zammit in 2012, with reverse-engineering for Digi 003 Rack.
36 */
37struct dot_state {
38	u8 carry;
39	u8 idx;
40	unsigned int off;
41};
42
43struct amdtp_dot {
44	unsigned int pcm_channels;
45	struct dot_state state;
46
47	struct snd_rawmidi_substream *midi[MAX_MIDI_PORTS];
48	int midi_fifo_used[MAX_MIDI_PORTS];
49	int midi_fifo_limit;
50};
51
52/*
53 * double-oh-three look up table
54 *
55 * @param idx index byte (audio-sample data) 0x00..0xff
56 * @param off channel offset shift
57 * @return salt to XOR with given data
58 */
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)
62static u8 dot_scrt(const u8 idx, const unsigned int off)
63{
64	/*
65	 * the length of the added pattern only depends on the lower nibble
66	 * of the last non-zero data
67	 */
68	static const u8 len[16] = {0, 1, 3, 5, 7, 9, 11, 13, 14,
69				   12, 10, 8, 6, 4, 2, 0};
70
71	/*
72	 * the lower nibble of the salt. Interleaved sequence.
73	 * this is walked backwards according to len[]
74	 */
75	static const u8 nib[15] = {0x8, 0x7, 0x9, 0x6, 0xa, 0x5, 0xb, 0x4,
76				   0xc, 0x3, 0xd, 0x2, 0xe, 0x1, 0xf};
77
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};
81
82	/*
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.
87	 */
88	static const u8 hio[16] = {0, 11, 12, 6, 7, 5, 1, 4,
89				   3, 0x00, 14, 13, 8, 9, 10, 2};
90
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];
94
95	if (len[ln] < off)
96		return 0x00;
97
98	return ((nib[14 + off - len[ln]]) | (hr << 4));
99}
100
101static void dot_encode_step(struct dot_state *state, __be32 *const buffer)
102{
103	u8 * const data = (u8 *) buffer;
104
105	if (data[MAGIC_DOT_BYTE] != 0x00) {
106		state->off = 0;
107		state->idx = data[MAGIC_DOT_BYTE] ^ state->carry;
108	}
109	data[MAGIC_DOT_BYTE] ^= state->carry;
110	state->carry = dot_scrt(state->idx, ++(state->off));
111}
112
113int amdtp_dot_set_parameters(struct amdtp_stream *s, unsigned int rate,
114			     unsigned int pcm_channels)
115{
116	struct amdtp_dot *p = s->protocol;
117	int err;
118
119	if (amdtp_stream_running(s))
120		return -EBUSY;
121
122	/*
123	 * A first data channel is for MIDI messages, the rest is Multi Bit
124	 * Linear Audio data channel.
125	 */
126	err = amdtp_stream_set_parameters(s, rate, pcm_channels + 1, 1);
127	if (err < 0)
128		return err;
129
130	s->ctx_data.rx.fdf = AMDTP_FDF_AM824 | s->sfc;
131
132	p->pcm_channels = pcm_channels;
133
134	/*
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().)
139	 */
140	p->midi_fifo_limit = rate - MIDI_BYTES_PER_SECOND * s->syt_interval + 1;
141
142	return 0;
143}
144
145static void write_pcm_s32(struct amdtp_stream *s, struct snd_pcm_substream *pcm,
146			  __be32 *buffer, unsigned int frames,
147			  unsigned int pcm_frames)
148{
149	struct amdtp_dot *p = s->protocol;
150	unsigned int channels = p->pcm_channels;
151	struct snd_pcm_runtime *runtime = pcm->runtime;
152	unsigned int pcm_buffer_pointer;
153	int remaining_frames;
154	const u32 *src;
155	int i, c;
156
157	pcm_buffer_pointer = s->pcm_buffer_pointer + pcm_frames;
158	pcm_buffer_pointer %= runtime->buffer_size;
159
160	src = (void *)runtime->dma_area +
161				frames_to_bytes(runtime, pcm_buffer_pointer);
162	remaining_frames = runtime->buffer_size - pcm_buffer_pointer;
163
164	buffer++;
165	for (i = 0; i < frames; ++i) {
166		for (c = 0; c < channels; ++c) {
167			buffer[c] = cpu_to_be32((*src >> 8) | 0x40000000);
168			dot_encode_step(&p->state, &buffer[c]);
169			src++;
170		}
171		buffer += s->data_block_quadlets;
172		if (--remaining_frames == 0)
173			src = (void *)runtime->dma_area;
174	}
175}
176
177static void read_pcm_s32(struct amdtp_stream *s, struct snd_pcm_substream *pcm,
178			 __be32 *buffer, unsigned int frames,
179			 unsigned int pcm_frames)
180{
181	struct amdtp_dot *p = s->protocol;
182	unsigned int channels = p->pcm_channels;
183	struct snd_pcm_runtime *runtime = pcm->runtime;
184	unsigned int pcm_buffer_pointer;
185	int remaining_frames;
186	u32 *dst;
187	int i, c;
188
189	pcm_buffer_pointer = s->pcm_buffer_pointer + pcm_frames;
190	pcm_buffer_pointer %= runtime->buffer_size;
191
192	dst  = (void *)runtime->dma_area +
193				frames_to_bytes(runtime, pcm_buffer_pointer);
194	remaining_frames = runtime->buffer_size - pcm_buffer_pointer;
195
196	buffer++;
197	for (i = 0; i < frames; ++i) {
198		for (c = 0; c < channels; ++c) {
199			*dst = be32_to_cpu(buffer[c]) << 8;
200			dst++;
201		}
202		buffer += s->data_block_quadlets;
203		if (--remaining_frames == 0)
204			dst = (void *)runtime->dma_area;
205	}
206}
207
208static void write_pcm_silence(struct amdtp_stream *s, __be32 *buffer,
209			      unsigned int data_blocks)
210{
211	struct amdtp_dot *p = s->protocol;
212	unsigned int channels, i, c;
213
214	channels = p->pcm_channels;
215
216	buffer++;
217	for (i = 0; i < data_blocks; ++i) {
218		for (c = 0; c < channels; ++c)
219			buffer[c] = cpu_to_be32(0x40000000);
220		buffer += s->data_block_quadlets;
221	}
222}
223
224static bool midi_ratelimit_per_packet(struct amdtp_stream *s, unsigned int port)
225{
226	struct amdtp_dot *p = s->protocol;
227	int used;
228
229	used = p->midi_fifo_used[port];
230	if (used == 0)
231		return true;
232
233	used -= MIDI_BYTES_PER_SECOND * s->syt_interval;
234	used = max(used, 0);
235	p->midi_fifo_used[port] = used;
236
237	return used < p->midi_fifo_limit;
238}
239
240static inline void midi_use_bytes(struct amdtp_stream *s,
241				  unsigned int port, unsigned int count)
242{
243	struct amdtp_dot *p = s->protocol;
244
245	p->midi_fifo_used[port] += amdtp_rate_table[s->sfc] * count;
246}
247
248static void write_midi_messages(struct amdtp_stream *s, __be32 *buffer,
249		unsigned int data_blocks, unsigned int data_block_counter)
250{
251	struct amdtp_dot *p = s->protocol;
252	unsigned int f, port;
253	int len;
254	u8 *b;
255
256	for (f = 0; f < data_blocks; f++) {
257		port = (data_block_counter + f) % 8;
258		b = (u8 *)&buffer[0];
259
260		len = 0;
261		if (port < MAX_MIDI_PORTS &&
262		    midi_ratelimit_per_packet(s, port) &&
263		    p->midi[port] != NULL)
264			len = snd_rawmidi_transmit(p->midi[port], b + 1, 2);
265
266		if (len > 0) {
267			/*
268			 * Upper 4 bits of LSB represent port number.
269			 * - 0000b: physical MIDI port 1.
270			 * - 0010b: physical MIDI port 2.
271			 * - 1110b: console MIDI port.
272			 */
273			if (port == 2)
274				b[3] = 0xe0;
275			else if (port == 1)
276				b[3] = 0x20;
277			else
278				b[3] = 0x00;
279			b[3] |= len;
280			midi_use_bytes(s, port, len);
281		} else {
282			b[1] = 0;
283			b[2] = 0;
284			b[3] = 0;
285		}
286		b[0] = 0x80;
287
288		buffer += s->data_block_quadlets;
289	}
290}
291
292static void read_midi_messages(struct amdtp_stream *s, __be32 *buffer,
293			       unsigned int data_blocks)
294{
295	struct amdtp_dot *p = s->protocol;
296	unsigned int f, port, len;
297	u8 *b;
298
299	for (f = 0; f < data_blocks; f++) {
300		b = (u8 *)&buffer[0];
301
302		len = b[3] & 0x0f;
303		if (len > 0) {
304			/*
305			 * Upper 4 bits of LSB represent port number.
306			 * - 0000b: physical MIDI port 1. Use port 0.
307			 * - 1110b: console MIDI port. Use port 2.
308			 */
309			if (b[3] >> 4 > 0)
310				port = 2;
311			else
312				port = 0;
313
314			if (port < MAX_MIDI_PORTS && p->midi[port])
315				snd_rawmidi_receive(p->midi[port], b + 1, len);
316		}
317
318		buffer += s->data_block_quadlets;
319	}
320}
321
322int amdtp_dot_add_pcm_hw_constraints(struct amdtp_stream *s,
323				     struct snd_pcm_runtime *runtime)
324{
325	int err;
326
327	/* This protocol delivers 24 bit data in 32bit data channel. */
328	err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
329	if (err < 0)
330		return err;
331
332	return amdtp_stream_add_pcm_hw_constraints(s, runtime);
333}
334
335void amdtp_dot_midi_trigger(struct amdtp_stream *s, unsigned int port,
336			  struct snd_rawmidi_substream *midi)
337{
338	struct amdtp_dot *p = s->protocol;
339
340	if (port < MAX_MIDI_PORTS)
341		WRITE_ONCE(p->midi[port], midi);
342}
343
344static void process_ir_ctx_payloads(struct amdtp_stream *s, const struct pkt_desc *desc,
345				    unsigned int count, struct snd_pcm_substream *pcm)
346{
347	unsigned int pcm_frames = 0;
348	int i;
349
350	for (i = 0; i < count; ++i) {
351		__be32 *buf = desc->ctx_payload;
352		unsigned int data_blocks = desc->data_blocks;
353
354		if (pcm) {
355			read_pcm_s32(s, pcm, buf, data_blocks, pcm_frames);
356			pcm_frames += data_blocks;
357		}
358
359		read_midi_messages(s, buf, data_blocks);
360
361		desc = amdtp_stream_next_packet_desc(s, desc);
362	}
363}
364
365static void process_it_ctx_payloads(struct amdtp_stream *s, const struct pkt_desc *desc,
366				    unsigned int count, struct snd_pcm_substream *pcm)
367{
368	unsigned int pcm_frames = 0;
369	int i;
370
371	for (i = 0; i < count; ++i) {
372		__be32 *buf = desc->ctx_payload;
373		unsigned int data_blocks = desc->data_blocks;
374
375		if (pcm) {
376			write_pcm_s32(s, pcm, buf, data_blocks, pcm_frames);
377			pcm_frames += data_blocks;
378		} else {
379			write_pcm_silence(s, buf, data_blocks);
380		}
381
382		write_midi_messages(s, buf, data_blocks,
383				    desc->data_block_counter);
384
385		desc = amdtp_stream_next_packet_desc(s, desc);
386	}
387}
388
389int amdtp_dot_init(struct amdtp_stream *s, struct fw_unit *unit,
390		 enum amdtp_stream_direction dir)
391{
392	amdtp_stream_process_ctx_payloads_t process_ctx_payloads;
393	unsigned int flags = CIP_NONBLOCKING | CIP_UNAWARE_SYT;
394
395	// Use different mode between incoming/outgoing.
396	if (dir == AMDTP_IN_STREAM)
397		process_ctx_payloads = process_ir_ctx_payloads;
398	else
399		process_ctx_payloads = process_it_ctx_payloads;
400
401	return amdtp_stream_init(s, unit, dir, flags, CIP_FMT_AM,
402				process_ctx_payloads, sizeof(struct amdtp_dot));
403}
404
405void amdtp_dot_reset(struct amdtp_stream *s)
406{
407	struct amdtp_dot *p = s->protocol;
408
409	p->state.carry = 0x00;
410	p->state.idx = 0x00;
411	p->state.off = 0;
412}
413