xref: /openbmc/linux/sound/mips/snd-n64.c (revision a544684b)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *   Sound driver for Nintendo 64.
4  *
5  *   Copyright 2021 Lauri Kasanen
6  */
7 
8 #include <linux/dma-mapping.h>
9 #include <linux/init.h>
10 #include <linux/interrupt.h>
11 #include <linux/io.h>
12 #include <linux/log2.h>
13 #include <linux/module.h>
14 #include <linux/platform_device.h>
15 #include <linux/spinlock.h>
16 
17 #include <sound/control.h>
18 #include <sound/core.h>
19 #include <sound/initval.h>
20 #include <sound/pcm.h>
21 #include <sound/pcm_params.h>
22 
23 MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>");
24 MODULE_DESCRIPTION("N64 Audio");
25 MODULE_LICENSE("GPL");
26 
27 #define AI_NTSC_DACRATE 48681812
28 #define AI_STATUS_BUSY  (1 << 30)
29 #define AI_STATUS_FULL  (1 << 31)
30 
31 #define AI_ADDR_REG 0
32 #define AI_LEN_REG 1
33 #define AI_CONTROL_REG 2
34 #define AI_STATUS_REG 3
35 #define AI_RATE_REG 4
36 #define AI_BITCLOCK_REG 5
37 
38 #define MI_INTR_REG 2
39 #define MI_MASK_REG 3
40 
41 #define MI_INTR_AI 0x04
42 
43 #define MI_MASK_CLR_AI 0x0010
44 #define MI_MASK_SET_AI 0x0020
45 
46 
47 struct n64audio {
48 	u32 __iomem *ai_reg_base;
49 	u32 __iomem *mi_reg_base;
50 
51 	void *ring_base;
52 	dma_addr_t ring_base_dma;
53 
54 	struct snd_card *card;
55 
56 	struct {
57 		struct snd_pcm_substream *substream;
58 		int pos, nextpos;
59 		u32 writesize;
60 		u32 bufsize;
61 		spinlock_t lock;
62 	} chan;
63 };
64 
n64audio_write_reg(struct n64audio * priv,const u8 reg,const u32 value)65 static void n64audio_write_reg(struct n64audio *priv, const u8 reg, const u32 value)
66 {
67 	writel(value, priv->ai_reg_base + reg);
68 }
69 
n64mi_write_reg(struct n64audio * priv,const u8 reg,const u32 value)70 static void n64mi_write_reg(struct n64audio *priv, const u8 reg, const u32 value)
71 {
72 	writel(value, priv->mi_reg_base + reg);
73 }
74 
n64mi_read_reg(struct n64audio * priv,const u8 reg)75 static u32 n64mi_read_reg(struct n64audio *priv, const u8 reg)
76 {
77 	return readl(priv->mi_reg_base + reg);
78 }
79 
n64audio_push(struct n64audio * priv)80 static void n64audio_push(struct n64audio *priv)
81 {
82 	struct snd_pcm_runtime *runtime = priv->chan.substream->runtime;
83 	unsigned long flags;
84 	u32 count;
85 
86 	spin_lock_irqsave(&priv->chan.lock, flags);
87 
88 	count = priv->chan.writesize;
89 
90 	memcpy(priv->ring_base + priv->chan.nextpos,
91 	       runtime->dma_area + priv->chan.nextpos, count);
92 
93 	/*
94 	 * The hw registers are double-buffered, and the IRQ fires essentially
95 	 * one period behind. The core only allows one period's distance, so we
96 	 * keep a private DMA buffer to afford two.
97 	 */
98 	n64audio_write_reg(priv, AI_ADDR_REG, priv->ring_base_dma + priv->chan.nextpos);
99 	barrier();
100 	n64audio_write_reg(priv, AI_LEN_REG, count);
101 
102 	priv->chan.nextpos += count;
103 	priv->chan.nextpos %= priv->chan.bufsize;
104 
105 	runtime->delay = runtime->period_size;
106 
107 	spin_unlock_irqrestore(&priv->chan.lock, flags);
108 }
109 
n64audio_isr(int irq,void * dev_id)110 static irqreturn_t n64audio_isr(int irq, void *dev_id)
111 {
112 	struct n64audio *priv = dev_id;
113 	const u32 intrs = n64mi_read_reg(priv, MI_INTR_REG);
114 	unsigned long flags;
115 
116 	// Check it's ours
117 	if (!(intrs & MI_INTR_AI))
118 		return IRQ_NONE;
119 
120 	n64audio_write_reg(priv, AI_STATUS_REG, 1);
121 
122 	if (priv->chan.substream && snd_pcm_running(priv->chan.substream)) {
123 		spin_lock_irqsave(&priv->chan.lock, flags);
124 
125 		priv->chan.pos = priv->chan.nextpos;
126 
127 		spin_unlock_irqrestore(&priv->chan.lock, flags);
128 
129 		snd_pcm_period_elapsed(priv->chan.substream);
130 		if (priv->chan.substream && snd_pcm_running(priv->chan.substream))
131 			n64audio_push(priv);
132 	}
133 
134 	return IRQ_HANDLED;
135 }
136 
137 static const struct snd_pcm_hardware n64audio_pcm_hw = {
138 	.info = (SNDRV_PCM_INFO_MMAP |
139 		 SNDRV_PCM_INFO_MMAP_VALID |
140 		 SNDRV_PCM_INFO_INTERLEAVED |
141 		 SNDRV_PCM_INFO_BLOCK_TRANSFER),
142 	.formats =          SNDRV_PCM_FMTBIT_S16_BE,
143 	.rates =            SNDRV_PCM_RATE_8000_48000,
144 	.rate_min =         8000,
145 	.rate_max =         48000,
146 	.channels_min =     2,
147 	.channels_max =     2,
148 	.buffer_bytes_max = 32768,
149 	.period_bytes_min = 1024,
150 	.period_bytes_max = 32768,
151 	.periods_min =      3,
152 	// 3 periods lets the double-buffering hw read one buffer behind safely
153 	.periods_max =      128,
154 };
155 
hw_rule_period_size(struct snd_pcm_hw_params * params,struct snd_pcm_hw_rule * rule)156 static int hw_rule_period_size(struct snd_pcm_hw_params *params,
157 			       struct snd_pcm_hw_rule *rule)
158 {
159 	struct snd_interval *c = hw_param_interval(params,
160 						   SNDRV_PCM_HW_PARAM_PERIOD_SIZE);
161 	int changed = 0;
162 
163 	/*
164 	 * The DMA unit has errata on (start + len) & 0x3fff == 0x2000.
165 	 * This constraint makes sure that the period size is not a power of two,
166 	 * which combined with dma_alloc_coherent aligning the buffer to the largest
167 	 * PoT <= size guarantees it won't be hit.
168 	 */
169 
170 	if (is_power_of_2(c->min)) {
171 		c->min += 2;
172 		changed = 1;
173 	}
174 	if (is_power_of_2(c->max)) {
175 		c->max -= 2;
176 		changed = 1;
177 	}
178 	if (snd_interval_checkempty(c)) {
179 		c->empty = 1;
180 		return -EINVAL;
181 	}
182 
183 	return changed;
184 }
185 
n64audio_pcm_open(struct snd_pcm_substream * substream)186 static int n64audio_pcm_open(struct snd_pcm_substream *substream)
187 {
188 	struct snd_pcm_runtime *runtime = substream->runtime;
189 	int err;
190 
191 	runtime->hw = n64audio_pcm_hw;
192 	err = snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
193 	if (err < 0)
194 		return err;
195 
196 	err = snd_pcm_hw_constraint_step(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 2);
197 	if (err < 0)
198 		return err;
199 
200 	err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
201 			    hw_rule_period_size, NULL, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, -1);
202 	if (err < 0)
203 		return err;
204 
205 	return 0;
206 }
207 
n64audio_pcm_prepare(struct snd_pcm_substream * substream)208 static int n64audio_pcm_prepare(struct snd_pcm_substream *substream)
209 {
210 	struct snd_pcm_runtime *runtime = substream->runtime;
211 	struct n64audio *priv = substream->pcm->private_data;
212 	u32 rate;
213 
214 	rate = ((2 * AI_NTSC_DACRATE / runtime->rate) + 1) / 2 - 1;
215 
216 	n64audio_write_reg(priv, AI_RATE_REG, rate);
217 
218 	rate /= 66;
219 	if (rate > 16)
220 		rate = 16;
221 	n64audio_write_reg(priv, AI_BITCLOCK_REG, rate - 1);
222 
223 	spin_lock_irq(&priv->chan.lock);
224 
225 	/* Setup the pseudo-dma transfer pointers.  */
226 	priv->chan.pos = 0;
227 	priv->chan.nextpos = 0;
228 	priv->chan.substream = substream;
229 	priv->chan.writesize = snd_pcm_lib_period_bytes(substream);
230 	priv->chan.bufsize = snd_pcm_lib_buffer_bytes(substream);
231 
232 	spin_unlock_irq(&priv->chan.lock);
233 	return 0;
234 }
235 
n64audio_pcm_trigger(struct snd_pcm_substream * substream,int cmd)236 static int n64audio_pcm_trigger(struct snd_pcm_substream *substream,
237 				int cmd)
238 {
239 	struct n64audio *priv = substream->pcm->private_data;
240 
241 	switch (cmd) {
242 	case SNDRV_PCM_TRIGGER_START:
243 		n64audio_push(substream->pcm->private_data);
244 		n64audio_write_reg(priv, AI_CONTROL_REG, 1);
245 		n64mi_write_reg(priv, MI_MASK_REG, MI_MASK_SET_AI);
246 		break;
247 	case SNDRV_PCM_TRIGGER_STOP:
248 		n64audio_write_reg(priv, AI_CONTROL_REG, 0);
249 		n64mi_write_reg(priv, MI_MASK_REG, MI_MASK_CLR_AI);
250 		break;
251 	default:
252 		return -EINVAL;
253 	}
254 	return 0;
255 }
256 
n64audio_pcm_pointer(struct snd_pcm_substream * substream)257 static snd_pcm_uframes_t n64audio_pcm_pointer(struct snd_pcm_substream *substream)
258 {
259 	struct n64audio *priv = substream->pcm->private_data;
260 
261 	return bytes_to_frames(substream->runtime,
262 			       priv->chan.pos);
263 }
264 
n64audio_pcm_close(struct snd_pcm_substream * substream)265 static int n64audio_pcm_close(struct snd_pcm_substream *substream)
266 {
267 	struct n64audio *priv = substream->pcm->private_data;
268 
269 	priv->chan.substream = NULL;
270 
271 	return 0;
272 }
273 
274 static const struct snd_pcm_ops n64audio_pcm_ops = {
275 	.open =		n64audio_pcm_open,
276 	.prepare =	n64audio_pcm_prepare,
277 	.trigger =	n64audio_pcm_trigger,
278 	.pointer =	n64audio_pcm_pointer,
279 	.close =	n64audio_pcm_close,
280 };
281 
282 /*
283  * The target device is embedded and RAM-constrained. We save RAM
284  * by initializing in __init code that gets dropped late in boot.
285  * For the same reason there is no module or unloading support.
286  */
n64audio_probe(struct platform_device * pdev)287 static int __init n64audio_probe(struct platform_device *pdev)
288 {
289 	struct snd_card *card;
290 	struct snd_pcm *pcm;
291 	struct n64audio *priv;
292 	int err, irq;
293 
294 	err = snd_card_new(&pdev->dev, SNDRV_DEFAULT_IDX1,
295 			   SNDRV_DEFAULT_STR1,
296 			   THIS_MODULE, sizeof(*priv), &card);
297 	if (err < 0)
298 		return err;
299 
300 	priv = card->private_data;
301 
302 	spin_lock_init(&priv->chan.lock);
303 
304 	priv->card = card;
305 
306 	priv->ring_base = dma_alloc_coherent(card->dev, 32 * 1024, &priv->ring_base_dma,
307 					     GFP_DMA|GFP_KERNEL);
308 	if (!priv->ring_base) {
309 		err = -ENOMEM;
310 		goto fail_card;
311 	}
312 
313 	priv->mi_reg_base = devm_platform_ioremap_resource(pdev, 0);
314 	if (IS_ERR(priv->mi_reg_base)) {
315 		err = PTR_ERR(priv->mi_reg_base);
316 		goto fail_dma_alloc;
317 	}
318 
319 	priv->ai_reg_base = devm_platform_ioremap_resource(pdev, 1);
320 	if (IS_ERR(priv->ai_reg_base)) {
321 		err = PTR_ERR(priv->ai_reg_base);
322 		goto fail_dma_alloc;
323 	}
324 
325 	err = snd_pcm_new(card, "N64 Audio", 0, 1, 0, &pcm);
326 	if (err < 0)
327 		goto fail_dma_alloc;
328 
329 	pcm->private_data = priv;
330 	strcpy(pcm->name, "N64 Audio");
331 
332 	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &n64audio_pcm_ops);
333 	snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_VMALLOC, card->dev, 0, 0);
334 
335 	strcpy(card->driver, "N64 Audio");
336 	strcpy(card->shortname, "N64 Audio");
337 	strcpy(card->longname, "N64 Audio");
338 
339 	irq = platform_get_irq(pdev, 0);
340 	if (irq < 0) {
341 		err = -EINVAL;
342 		goto fail_dma_alloc;
343 	}
344 	if (devm_request_irq(&pdev->dev, irq, n64audio_isr,
345 				IRQF_SHARED, "N64 Audio", priv)) {
346 		err = -EBUSY;
347 		goto fail_dma_alloc;
348 	}
349 
350 	err = snd_card_register(card);
351 	if (err < 0)
352 		goto fail_dma_alloc;
353 
354 	return 0;
355 
356 fail_dma_alloc:
357 	dma_free_coherent(card->dev, 32 * 1024, priv->ring_base, priv->ring_base_dma);
358 
359 fail_card:
360 	snd_card_free(card);
361 	return err;
362 }
363 
364 static struct platform_driver n64audio_driver = {
365 	.driver = {
366 		.name = "n64audio",
367 	},
368 };
369 
n64audio_init(void)370 static int __init n64audio_init(void)
371 {
372 	return platform_driver_probe(&n64audio_driver, n64audio_probe);
373 }
374 
375 module_init(n64audio_init);
376