1 /*
2  * amdtp-dot.c - a part of driver for Digidesign Digi 002/003 family
3  *
4  * Copyright (c) 2014-2015 Takashi Sakamoto
5  * Copyright (C) 2012 Robin Gareus <robin@gareus.org>
6  * Copyright (C) 2012 Damien Zammit <damien@zamaudio.com>
7  *
8  * Licensed under the terms of the GNU General Public License, version 2.
9  */
10 
11 #include <sound/pcm.h>
12 #include "digi00x.h"
13 
14 #define CIP_FMT_AM		0x10
15 
16 /* 'Clock-based rate control mode' is just supported. */
17 #define AMDTP_FDF_AM824		0x00
18 
19 /*
20  * Nominally 3125 bytes/second, but the MIDI port's clock might be
21  * 1% too slow, and the bus clock 100 ppm too fast.
22  */
23 #define MIDI_BYTES_PER_SECOND	3093
24 
25 /*
26  * Several devices look only at the first eight data blocks.
27  * In any case, this is more than enough for the MIDI data rate.
28  */
29 #define MAX_MIDI_RX_BLOCKS	8
30 
31 /* 3 = MAX(DOT_MIDI_IN_PORTS, DOT_MIDI_OUT_PORTS) + 1. */
32 #define MAX_MIDI_PORTS		3
33 
34 /*
35  * The double-oh-three algorithm was discovered by Robin Gareus and Damien
36  * Zammit in 2012, with reverse-engineering for Digi 003 Rack.
37  */
38 struct dot_state {
39 	u8 carry;
40 	u8 idx;
41 	unsigned int off;
42 };
43 
44 struct amdtp_dot {
45 	unsigned int pcm_channels;
46 	struct dot_state state;
47 
48 	struct snd_rawmidi_substream *midi[MAX_MIDI_PORTS];
49 	int midi_fifo_used[MAX_MIDI_PORTS];
50 	int midi_fifo_limit;
51 };
52 
53 /*
54  * double-oh-three look up table
55  *
56  * @param idx index byte (audio-sample data) 0x00..0xff
57  * @param off channel offset shift
58  * @return salt to XOR with given data
59  */
60 #define BYTE_PER_SAMPLE (4)
61 #define MAGIC_DOT_BYTE (2)
62 #define MAGIC_BYTE_OFF(x) (((x) * BYTE_PER_SAMPLE) + MAGIC_DOT_BYTE)
63 static u8 dot_scrt(const u8 idx, const unsigned int off)
64 {
65 	/*
66 	 * the length of the added pattern only depends on the lower nibble
67 	 * of the last non-zero data
68 	 */
69 	static const u8 len[16] = {0, 1, 3, 5, 7, 9, 11, 13, 14,
70 				   12, 10, 8, 6, 4, 2, 0};
71 
72 	/*
73 	 * the lower nibble of the salt. Interleaved sequence.
74 	 * this is walked backwards according to len[]
75 	 */
76 	static const u8 nib[15] = {0x8, 0x7, 0x9, 0x6, 0xa, 0x5, 0xb, 0x4,
77 				   0xc, 0x3, 0xd, 0x2, 0xe, 0x1, 0xf};
78 
79 	/* circular list for the salt's hi nibble. */
80 	static const u8 hir[15] = {0x0, 0x6, 0xf, 0x8, 0x7, 0x5, 0x3, 0x4,
81 				   0xc, 0xd, 0xe, 0x1, 0x2, 0xb, 0xa};
82 
83 	/*
84 	 * start offset for upper nibble mapping.
85 	 * note: 9 is /special/. In the case where the high nibble == 0x9,
86 	 * hir[] is not used and - coincidentally - the salt's hi nibble is
87 	 * 0x09 regardless of the offset.
88 	 */
89 	static const u8 hio[16] = {0, 11, 12, 6, 7, 5, 1, 4,
90 				   3, 0x00, 14, 13, 8, 9, 10, 2};
91 
92 	const u8 ln = idx & 0xf;
93 	const u8 hn = (idx >> 4) & 0xf;
94 	const u8 hr = (hn == 0x9) ? 0x9 : hir[(hio[hn] + off) % 15];
95 
96 	if (len[ln] < off)
97 		return 0x00;
98 
99 	return ((nib[14 + off - len[ln]]) | (hr << 4));
100 }
101 
102 static void dot_encode_step(struct dot_state *state, __be32 *const buffer)
103 {
104 	u8 * const data = (u8 *) buffer;
105 
106 	if (data[MAGIC_DOT_BYTE] != 0x00) {
107 		state->off = 0;
108 		state->idx = data[MAGIC_DOT_BYTE] ^ state->carry;
109 	}
110 	data[MAGIC_DOT_BYTE] ^= state->carry;
111 	state->carry = dot_scrt(state->idx, ++(state->off));
112 }
113 
114 int amdtp_dot_set_parameters(struct amdtp_stream *s, unsigned int rate,
115 			     unsigned int pcm_channels)
116 {
117 	struct amdtp_dot *p = s->protocol;
118 	int err;
119 
120 	if (amdtp_stream_running(s))
121 		return -EBUSY;
122 
123 	/*
124 	 * A first data channel is for MIDI messages, the rest is Multi Bit
125 	 * Linear Audio data channel.
126 	 */
127 	err = amdtp_stream_set_parameters(s, rate, pcm_channels + 1);
128 	if (err < 0)
129 		return err;
130 
131 	s->fdf = AMDTP_FDF_AM824 | s->sfc;
132 
133 	p->pcm_channels = pcm_channels;
134 
135 	/*
136 	 * We do not know the actual MIDI FIFO size of most devices.  Just
137 	 * assume two bytes, i.e., one byte can be received over the bus while
138 	 * the previous one is transmitted over MIDI.
139 	 * (The value here is adjusted for midi_ratelimit_per_packet().)
140 	 */
141 	p->midi_fifo_limit = rate - MIDI_BYTES_PER_SECOND * s->syt_interval + 1;
142 
143 	return 0;
144 }
145 
146 static void write_pcm_s32(struct amdtp_stream *s, struct snd_pcm_substream *pcm,
147 			  __be32 *buffer, unsigned int frames)
148 {
149 	struct amdtp_dot *p = s->protocol;
150 	struct snd_pcm_runtime *runtime = pcm->runtime;
151 	unsigned int channels, remaining_frames, i, c;
152 	const u32 *src;
153 
154 	channels = p->pcm_channels;
155 	src = (void *)runtime->dma_area +
156 			frames_to_bytes(runtime, s->pcm_buffer_pointer);
157 	remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
158 
159 	buffer++;
160 	for (i = 0; i < frames; ++i) {
161 		for (c = 0; c < channels; ++c) {
162 			buffer[c] = cpu_to_be32((*src >> 8) | 0x40000000);
163 			dot_encode_step(&p->state, &buffer[c]);
164 			src++;
165 		}
166 		buffer += s->data_block_quadlets;
167 		if (--remaining_frames == 0)
168 			src = (void *)runtime->dma_area;
169 	}
170 }
171 
172 static void read_pcm_s32(struct amdtp_stream *s, struct snd_pcm_substream *pcm,
173 			 __be32 *buffer, unsigned int frames)
174 {
175 	struct amdtp_dot *p = s->protocol;
176 	struct snd_pcm_runtime *runtime = pcm->runtime;
177 	unsigned int channels, remaining_frames, i, c;
178 	u32 *dst;
179 
180 	channels = p->pcm_channels;
181 	dst  = (void *)runtime->dma_area +
182 			frames_to_bytes(runtime, s->pcm_buffer_pointer);
183 	remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
184 
185 	buffer++;
186 	for (i = 0; i < frames; ++i) {
187 		for (c = 0; c < channels; ++c) {
188 			*dst = be32_to_cpu(buffer[c]) << 8;
189 			dst++;
190 		}
191 		buffer += s->data_block_quadlets;
192 		if (--remaining_frames == 0)
193 			dst = (void *)runtime->dma_area;
194 	}
195 }
196 
197 static void write_pcm_silence(struct amdtp_stream *s, __be32 *buffer,
198 			      unsigned int data_blocks)
199 {
200 	struct amdtp_dot *p = s->protocol;
201 	unsigned int channels, i, c;
202 
203 	channels = p->pcm_channels;
204 
205 	buffer++;
206 	for (i = 0; i < data_blocks; ++i) {
207 		for (c = 0; c < channels; ++c)
208 			buffer[c] = cpu_to_be32(0x40000000);
209 		buffer += s->data_block_quadlets;
210 	}
211 }
212 
213 static bool midi_ratelimit_per_packet(struct amdtp_stream *s, unsigned int port)
214 {
215 	struct amdtp_dot *p = s->protocol;
216 	int used;
217 
218 	used = p->midi_fifo_used[port];
219 	if (used == 0)
220 		return true;
221 
222 	used -= MIDI_BYTES_PER_SECOND * s->syt_interval;
223 	used = max(used, 0);
224 	p->midi_fifo_used[port] = used;
225 
226 	return used < p->midi_fifo_limit;
227 }
228 
229 static inline void midi_use_bytes(struct amdtp_stream *s,
230 				  unsigned int port, unsigned int count)
231 {
232 	struct amdtp_dot *p = s->protocol;
233 
234 	p->midi_fifo_used[port] += amdtp_rate_table[s->sfc] * count;
235 }
236 
237 static void write_midi_messages(struct amdtp_stream *s, __be32 *buffer,
238 				unsigned int data_blocks)
239 {
240 	struct amdtp_dot *p = s->protocol;
241 	unsigned int f, port;
242 	int len;
243 	u8 *b;
244 
245 	for (f = 0; f < data_blocks; f++) {
246 		port = (s->data_block_counter + f) % 8;
247 		b = (u8 *)&buffer[0];
248 
249 		len = 0;
250 		if (port < MAX_MIDI_PORTS &&
251 		    midi_ratelimit_per_packet(s, port) &&
252 		    p->midi[port] != NULL)
253 			len = snd_rawmidi_transmit(p->midi[port], b + 1, 2);
254 
255 		if (len > 0) {
256 			/*
257 			 * Upper 4 bits of LSB represent port number.
258 			 * - 0000b: physical MIDI port 1.
259 			 * - 0010b: physical MIDI port 2.
260 			 * - 1110b: console MIDI port.
261 			 */
262 			if (port == 2)
263 				b[3] = 0xe0;
264 			else if (port == 1)
265 				b[3] = 0x20;
266 			else
267 				b[3] = 0x00;
268 			b[3] |= len;
269 			midi_use_bytes(s, port, len);
270 		} else {
271 			b[1] = 0;
272 			b[2] = 0;
273 			b[3] = 0;
274 		}
275 		b[0] = 0x80;
276 
277 		buffer += s->data_block_quadlets;
278 	}
279 }
280 
281 static void read_midi_messages(struct amdtp_stream *s, __be32 *buffer,
282 			       unsigned int data_blocks)
283 {
284 	struct amdtp_dot *p = s->protocol;
285 	unsigned int f, port, len;
286 	u8 *b;
287 
288 	for (f = 0; f < data_blocks; f++) {
289 		b = (u8 *)&buffer[0];
290 
291 		len = b[3] & 0x0f;
292 		if (len > 0) {
293 			/*
294 			 * Upper 4 bits of LSB represent port number.
295 			 * - 0000b: physical MIDI port 1. Use port 0.
296 			 * - 1110b: console MIDI port. Use port 2.
297 			 */
298 			if (b[3] >> 4 > 0)
299 				port = 2;
300 			else
301 				port = 0;
302 
303 			if (port < MAX_MIDI_PORTS && p->midi[port])
304 				snd_rawmidi_receive(p->midi[port], b + 1, len);
305 		}
306 
307 		buffer += s->data_block_quadlets;
308 	}
309 }
310 
311 int amdtp_dot_add_pcm_hw_constraints(struct amdtp_stream *s,
312 				     struct snd_pcm_runtime *runtime)
313 {
314 	int err;
315 
316 	/* This protocol delivers 24 bit data in 32bit data channel. */
317 	err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
318 	if (err < 0)
319 		return err;
320 
321 	return amdtp_stream_add_pcm_hw_constraints(s, runtime);
322 }
323 
324 void amdtp_dot_midi_trigger(struct amdtp_stream *s, unsigned int port,
325 			  struct snd_rawmidi_substream *midi)
326 {
327 	struct amdtp_dot *p = s->protocol;
328 
329 	if (port < MAX_MIDI_PORTS)
330 		ACCESS_ONCE(p->midi[port]) = midi;
331 }
332 
333 static unsigned int process_tx_data_blocks(struct amdtp_stream *s,
334 					   __be32 *buffer,
335 					   unsigned int data_blocks,
336 					   unsigned int *syt)
337 {
338 	struct snd_pcm_substream *pcm;
339 	unsigned int pcm_frames;
340 
341 	pcm = ACCESS_ONCE(s->pcm);
342 	if (pcm) {
343 		read_pcm_s32(s, pcm, buffer, data_blocks);
344 		pcm_frames = data_blocks;
345 	} else {
346 		pcm_frames = 0;
347 	}
348 
349 	read_midi_messages(s, buffer, data_blocks);
350 
351 	return pcm_frames;
352 }
353 
354 static unsigned int process_rx_data_blocks(struct amdtp_stream *s,
355 					   __be32 *buffer,
356 					   unsigned int data_blocks,
357 					   unsigned int *syt)
358 {
359 	struct snd_pcm_substream *pcm;
360 	unsigned int pcm_frames;
361 
362 	pcm = ACCESS_ONCE(s->pcm);
363 	if (pcm) {
364 		write_pcm_s32(s, pcm, buffer, data_blocks);
365 		pcm_frames = data_blocks;
366 	} else {
367 		write_pcm_silence(s, buffer, data_blocks);
368 		pcm_frames = 0;
369 	}
370 
371 	write_midi_messages(s, buffer, data_blocks);
372 
373 	return pcm_frames;
374 }
375 
376 int amdtp_dot_init(struct amdtp_stream *s, struct fw_unit *unit,
377 		 enum amdtp_stream_direction dir)
378 {
379 	amdtp_stream_process_data_blocks_t process_data_blocks;
380 	enum cip_flags flags;
381 
382 	/* Use different mode between incoming/outgoing. */
383 	if (dir == AMDTP_IN_STREAM) {
384 		flags = CIP_NONBLOCKING;
385 		process_data_blocks = process_tx_data_blocks;
386 	} else {
387 		flags = CIP_BLOCKING;
388 		process_data_blocks = process_rx_data_blocks;
389 	}
390 
391 	return amdtp_stream_init(s, unit, dir, flags, CIP_FMT_AM,
392 				 process_data_blocks, sizeof(struct amdtp_dot));
393 }
394 
395 void amdtp_dot_reset(struct amdtp_stream *s)
396 {
397 	struct amdtp_dot *p = s->protocol;
398 
399 	p->state.carry = 0x00;
400 	p->state.idx = 0x00;
401 	p->state.off = 0;
402 }
403