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 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 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 75 static u32 n64mi_read_reg(struct n64audio *priv, const u8 reg) 76 { 77 return readl(priv->mi_reg_base + reg); 78 } 79 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 } 109 110 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 }; 155 156 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 } 185 186 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 } 207 208 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 } 235 236 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 } 256 257 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 } 264 265 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 */ 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 struct resource *res; 293 int err; 294 295 err = snd_card_new(&pdev->dev, SNDRV_DEFAULT_IDX1, 296 SNDRV_DEFAULT_STR1, 297 THIS_MODULE, sizeof(*priv), &card); 298 if (err < 0) 299 return err; 300 301 priv = card->private_data; 302 303 spin_lock_init(&priv->chan.lock); 304 305 priv->card = card; 306 307 priv->ring_base = dma_alloc_coherent(card->dev, 32 * 1024, &priv->ring_base_dma, 308 GFP_DMA|GFP_KERNEL); 309 if (!priv->ring_base) { 310 err = -ENOMEM; 311 goto fail_card; 312 } 313 314 priv->mi_reg_base = devm_platform_ioremap_resource(pdev, 0); 315 if (IS_ERR(priv->mi_reg_base)) { 316 err = PTR_ERR(priv->mi_reg_base); 317 goto fail_dma_alloc; 318 } 319 320 priv->ai_reg_base = devm_platform_ioremap_resource(pdev, 1); 321 if (IS_ERR(priv->ai_reg_base)) { 322 err = PTR_ERR(priv->ai_reg_base); 323 goto fail_dma_alloc; 324 } 325 326 err = snd_pcm_new(card, "N64 Audio", 0, 1, 0, &pcm); 327 if (err < 0) 328 goto fail_dma_alloc; 329 330 pcm->private_data = priv; 331 strcpy(pcm->name, "N64 Audio"); 332 333 snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &n64audio_pcm_ops); 334 snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_VMALLOC, card->dev, 0, 0); 335 336 strcpy(card->driver, "N64 Audio"); 337 strcpy(card->shortname, "N64 Audio"); 338 strcpy(card->longname, "N64 Audio"); 339 340 res = platform_get_resource(pdev, IORESOURCE_IRQ, 0); 341 if (!res) { 342 err = -EINVAL; 343 goto fail_dma_alloc; 344 } 345 if (devm_request_irq(&pdev->dev, res->start, n64audio_isr, 346 IRQF_SHARED, "N64 Audio", priv)) { 347 err = -EBUSY; 348 goto fail_dma_alloc; 349 } 350 351 err = snd_card_register(card); 352 if (err < 0) 353 goto fail_dma_alloc; 354 355 return 0; 356 357 fail_dma_alloc: 358 dma_free_coherent(card->dev, 32 * 1024, priv->ring_base, priv->ring_base_dma); 359 360 fail_card: 361 snd_card_free(card); 362 return err; 363 } 364 365 static struct platform_driver n64audio_driver = { 366 .driver = { 367 .name = "n64audio", 368 }, 369 }; 370 371 static int __init n64audio_init(void) 372 { 373 return platform_driver_probe(&n64audio_driver, n64audio_probe); 374 } 375 376 module_init(n64audio_init); 377