sound/mips/snd-n64.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  *   Sound driver for Nintendo 64.
  *
  *   Copyright 2021 Lauri Kasanen
  */

 #include <linux/dma-mapping.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/log2.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/spinlock.h>

 #include <sound/control.h>
 #include <sound/core.h>
 #include <sound/initval.h>
 #include <sound/pcm.h>
 #include <sound/pcm_params.h>

 MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>");
 MODULE_DESCRIPTION("N64 Audio");
 MODULE_LICENSE("GPL");

 #define AI_NTSC_DACRATE 48681812
 #define AI_STATUS_BUSY  (1 << 30)
 #define AI_STATUS_FULL  (1 << 31)

 #define AI_ADDR_REG 0
 #define AI_LEN_REG 1
 #define AI_CONTROL_REG 2
 #define AI_STATUS_REG 3
 #define AI_RATE_REG 4
 #define AI_BITCLOCK_REG 5

 #define MI_INTR_REG 2
 #define MI_MASK_REG 3

 #define MI_INTR_AI 0x04

 #define MI_MASK_CLR_AI 0x0010
 #define MI_MASK_SET_AI 0x0020


 struct n64audio {
 	u32 __iomem *ai_reg_base;
 	u32 __iomem *mi_reg_base;

 	void *ring_base;
 	dma_addr_t ring_base_dma;

 	struct snd_card *card;

 	struct {
 		struct snd_pcm_substream *substream;
 		int pos, nextpos;
 		u32 writesize;
 		u32 bufsize;
 		spinlock_t lock;
 	} chan;
 };

 static void n64audio_write_reg(struct n64audio *priv, const u8 reg, const u32 value)
 {
 	writel(value, priv->ai_reg_base + reg);
 }

 static void n64mi_write_reg(struct n64audio *priv, const u8 reg, const u32 value)
 {
 	writel(value, priv->mi_reg_base + reg);
 }

 static u32 n64mi_read_reg(struct n64audio *priv, const u8 reg)
 {
 	return readl(priv->mi_reg_base + reg);
 }

 static void n64audio_push(struct n64audio *priv)
 {
 	struct snd_pcm_runtime *runtime = priv->chan.substream->runtime;
 	unsigned long flags;
 	u32 count;

 	spin_lock_irqsave(&priv->chan.lock, flags);

 	count = priv->chan.writesize;

 	memcpy(priv->ring_base + priv->chan.nextpos,
 	       runtime->dma_area + priv->chan.nextpos, count);

 	/*
 	 * The hw registers are double-buffered, and the IRQ fires essentially
 	 * one period behind. The core only allows one period's distance, so we
 	 * keep a private DMA buffer to afford two.
 	 */
 	n64audio_write_reg(priv, AI_ADDR_REG, priv->ring_base_dma + priv->chan.nextpos);
 	barrier();
 	n64audio_write_reg(priv, AI_LEN_REG, count);

 	priv->chan.nextpos += count;
 	priv->chan.nextpos %= priv->chan.bufsize;

 	runtime->delay = runtime->period_size;

 	spin_unlock_irqrestore(&priv->chan.lock, flags);
 }

 static irqreturn_t n64audio_isr(int irq, void *dev_id)
 {
 	struct n64audio *priv = dev_id;
 	const u32 intrs = n64mi_read_reg(priv, MI_INTR_REG);
 	unsigned long flags;

 	// Check it's ours
 	if (!(intrs & MI_INTR_AI))
 		return IRQ_NONE;

 	n64audio_write_reg(priv, AI_STATUS_REG, 1);

 	if (priv->chan.substream && snd_pcm_running(priv->chan.substream)) {
 		spin_lock_irqsave(&priv->chan.lock, flags);

 		priv->chan.pos = priv->chan.nextpos;

 		spin_unlock_irqrestore(&priv->chan.lock, flags);

 		snd_pcm_period_elapsed(priv->chan.substream);
 		if (priv->chan.substream && snd_pcm_running(priv->chan.substream))
 			n64audio_push(priv);
 	}

 	return IRQ_HANDLED;
 }

 static const struct snd_pcm_hardware n64audio_pcm_hw = {
 	.info = (SNDRV_PCM_INFO_MMAP |
 		 SNDRV_PCM_INFO_MMAP_VALID |
 		 SNDRV_PCM_INFO_INTERLEAVED |
 		 SNDRV_PCM_INFO_BLOCK_TRANSFER),
 	.formats =          SNDRV_PCM_FMTBIT_S16_BE,
 	.rates =            SNDRV_PCM_RATE_8000_48000,
 	.rate_min =         8000,
 	.rate_max =         48000,
 	.channels_min =     2,
 	.channels_max =     2,
 	.buffer_bytes_max = 32768,
 	.period_bytes_min = 1024,
 	.period_bytes_max = 32768,
 	.periods_min =      3,
 	// 3 periods lets the double-buffering hw read one buffer behind safely
 	.periods_max =      128,
 };

 static int hw_rule_period_size(struct snd_pcm_hw_params *params,
 			       struct snd_pcm_hw_rule *rule)
 {
 	struct snd_interval *c = hw_param_interval(params,
 						   SNDRV_PCM_HW_PARAM_PERIOD_SIZE);
 	int changed = 0;

 	/*
 	 * The DMA unit has errata on (start + len) & 0x3fff == 0x2000.
 	 * This constraint makes sure that the period size is not a power of two,
 	 * which combined with dma_alloc_coherent aligning the buffer to the largest
 	 * PoT <= size guarantees it won't be hit.
 	 */

 	if (is_power_of_2(c->min)) {
 		c->min += 2;
 		changed = 1;
 	}
 	if (is_power_of_2(c->max)) {
 		c->max -= 2;
 		changed = 1;
 	}
 	if (snd_interval_checkempty(c)) {
 		c->empty = 1;
 		return -EINVAL;
 	}

 	return changed;
 }

 static int n64audio_pcm_open(struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	int err;

 	runtime->hw = n64audio_pcm_hw;
 	err = snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
 	if (err < 0)
 		return err;

 	err = snd_pcm_hw_constraint_step(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 2);
 	if (err < 0)
 		return err;

 	err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
 			    hw_rule_period_size, NULL, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, -1);
 	if (err < 0)
 		return err;

 	return 0;
 }

 static int n64audio_pcm_prepare(struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct n64audio *priv = substream->pcm->private_data;
 	u32 rate;

 	rate = ((2 * AI_NTSC_DACRATE / runtime->rate) + 1) / 2 - 1;

 	n64audio_write_reg(priv, AI_RATE_REG, rate);

 	rate /= 66;
 	if (rate > 16)
 		rate = 16;
 	n64audio_write_reg(priv, AI_BITCLOCK_REG, rate - 1);

 	spin_lock_irq(&priv->chan.lock);

 	/* Setup the pseudo-dma transfer pointers.  */
 	priv->chan.pos = 0;
 	priv->chan.nextpos = 0;
 	priv->chan.substream = substream;
 	priv->chan.writesize = snd_pcm_lib_period_bytes(substream);
 	priv->chan.bufsize = snd_pcm_lib_buffer_bytes(substream);

 	spin_unlock_irq(&priv->chan.lock);
 	return 0;
 }

 static int n64audio_pcm_trigger(struct snd_pcm_substream *substream,
 				int cmd)
 {
 	struct n64audio *priv = substream->pcm->private_data;

 	switch (cmd) {
 	case SNDRV_PCM_TRIGGER_START:
 		n64audio_push(substream->pcm->private_data);
 		n64audio_write_reg(priv, AI_CONTROL_REG, 1);
 		n64mi_write_reg(priv, MI_MASK_REG, MI_MASK_SET_AI);
 		break;
 	case SNDRV_PCM_TRIGGER_STOP:
 		n64audio_write_reg(priv, AI_CONTROL_REG, 0);
 		n64mi_write_reg(priv, MI_MASK_REG, MI_MASK_CLR_AI);
 		break;
 	default:
 		return -EINVAL;
 	}
 	return 0;
 }

 static snd_pcm_uframes_t n64audio_pcm_pointer(struct snd_pcm_substream *substream)
 {
 	struct n64audio *priv = substream->pcm->private_data;

 	return bytes_to_frames(substream->runtime,
 			       priv->chan.pos);
 }

 static int n64audio_pcm_close(struct snd_pcm_substream *substream)
 {
 	struct n64audio *priv = substream->pcm->private_data;

 	priv->chan.substream = NULL;

 	return 0;
 }

 static const struct snd_pcm_ops n64audio_pcm_ops = {
 	.open =		n64audio_pcm_open,
 	.prepare =	n64audio_pcm_prepare,
 	.trigger =	n64audio_pcm_trigger,
 	.pointer =	n64audio_pcm_pointer,
 	.close =	n64audio_pcm_close,
 };

 /*
  * The target device is embedded and RAM-constrained. We save RAM
  * by initializing in __init code that gets dropped late in boot.
  * For the same reason there is no module or unloading support.
  */
 static int __init n64audio_probe(struct platform_device *pdev)
 {
 	struct snd_card *card;
 	struct snd_pcm *pcm;
 	struct n64audio *priv;
 	struct resource *res;
 	int err;

 	err = snd_card_new(&pdev->dev, SNDRV_DEFAULT_IDX1,
 			   SNDRV_DEFAULT_STR1,
 			   THIS_MODULE, sizeof(*priv), &card);
 	if (err < 0)
 		return err;

 	priv = card->private_data;

 	spin_lock_init(&priv->chan.lock);

 	priv->card = card;

 	priv->ring_base = dma_alloc_coherent(card->dev, 32 * 1024, &priv->ring_base_dma,
 					     GFP_DMA|GFP_KERNEL);
 	if (!priv->ring_base) {
 		err = -ENOMEM;
 		goto fail_card;
 	}

 	priv->mi_reg_base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(priv->mi_reg_base)) {
 		err = PTR_ERR(priv->mi_reg_base);
 		goto fail_dma_alloc;
 	}

 	priv->ai_reg_base = devm_platform_ioremap_resource(pdev, 1);
 	if (IS_ERR(priv->ai_reg_base)) {
 		err = PTR_ERR(priv->ai_reg_base);
 		goto fail_dma_alloc;
 	}

 	err = snd_pcm_new(card, "N64 Audio", 0, 1, 0, &pcm);
 	if (err < 0)
 		goto fail_dma_alloc;

 	pcm->private_data = priv;
 	strcpy(pcm->name, "N64 Audio");

 	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &n64audio_pcm_ops);
 	snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_VMALLOC, card->dev, 0, 0);

 	strcpy(card->driver, "N64 Audio");
 	strcpy(card->shortname, "N64 Audio");
 	strcpy(card->longname, "N64 Audio");

 	res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 	if (devm_request_irq(&pdev->dev, res->start, n64audio_isr,
 				IRQF_SHARED, "N64 Audio", priv)) {
 		err = -EBUSY;
 		goto fail_dma_alloc;
 	}

 	err = snd_card_register(card);
 	if (err < 0)
 		goto fail_dma_alloc;

 	return 0;

 fail_dma_alloc:
 	dma_free_coherent(card->dev, 32 * 1024, priv->ring_base, priv->ring_base_dma);

 fail_card:
 	snd_card_free(card);
 	return err;
 }

 static struct platform_driver n64audio_driver = {
 	.driver = {
 		.name = "n64audio",
 	},
 };

 static int __init n64audio_init(void)
 {
 	return platform_driver_probe(&n64audio_driver, n64audio_probe);
 }

 module_init(n64audio_init);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Sound driver for Nintendo 64.
	*
	* Copyright 2021 Lauri Kasanen
	*/

	#include <linux/dma-mapping.h>
	#include <linux/init.h>
	#include <linux/interrupt.h>
	#include <linux/io.h>
	#include <linux/log2.h>
	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/spinlock.h>

	#include <sound/control.h>
	#include <sound/core.h>
	#include <sound/initval.h>
	#include <sound/pcm.h>
	#include <sound/pcm_params.h>

	MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>");
	MODULE_DESCRIPTION("N64 Audio");
	MODULE_LICENSE("GPL");

	#define AI_NTSC_DACRATE 48681812
	#define AI_STATUS_BUSY (1 << 30)
	#define AI_STATUS_FULL (1 << 31)

	#define AI_ADDR_REG 0
	#define AI_LEN_REG 1
	#define AI_CONTROL_REG 2
	#define AI_STATUS_REG 3
	#define AI_RATE_REG 4
	#define AI_BITCLOCK_REG 5

	#define MI_INTR_REG 2
	#define MI_MASK_REG 3

	#define MI_INTR_AI 0x04

	#define MI_MASK_CLR_AI 0x0010
	#define MI_MASK_SET_AI 0x0020


	struct n64audio {
	u32 __iomem *ai_reg_base;
	u32 __iomem *mi_reg_base;

	void *ring_base;
	dma_addr_t ring_base_dma;

	struct snd_card *card;

	struct {
	struct snd_pcm_substream *substream;
	int pos, nextpos;
	u32 writesize;
	u32 bufsize;
	spinlock_t lock;
	} chan;
	};

	static void n64audio_write_reg(struct n64audio *priv, const u8 reg, const u32 value)
	{
	writel(value, priv->ai_reg_base + reg);
	}

	static void n64mi_write_reg(struct n64audio *priv, const u8 reg, const u32 value)
	{
	writel(value, priv->mi_reg_base + reg);
	}

	static u32 n64mi_read_reg(struct n64audio *priv, const u8 reg)
	{
	return readl(priv->mi_reg_base + reg);
	}

	static void n64audio_push(struct n64audio *priv)
	{
	struct snd_pcm_runtime *runtime = priv->chan.substream->runtime;
	unsigned long flags;
	u32 count;

	spin_lock_irqsave(&priv->chan.lock, flags);

	count = priv->chan.writesize;

	memcpy(priv->ring_base + priv->chan.nextpos,
	runtime->dma_area + priv->chan.nextpos, count);

	/*
	* The hw registers are double-buffered, and the IRQ fires essentially
	* one period behind. The core only allows one period's distance, so we
	* keep a private DMA buffer to afford two.
	*/
	n64audio_write_reg(priv, AI_ADDR_REG, priv->ring_base_dma + priv->chan.nextpos);
	barrier();
	n64audio_write_reg(priv, AI_LEN_REG, count);

	priv->chan.nextpos += count;
	priv->chan.nextpos %= priv->chan.bufsize;

	runtime->delay = runtime->period_size;

	spin_unlock_irqrestore(&priv->chan.lock, flags);
	}

	static irqreturn_t n64audio_isr(int irq, void *dev_id)
	{
	struct n64audio *priv = dev_id;
	const u32 intrs = n64mi_read_reg(priv, MI_INTR_REG);
	unsigned long flags;

	// Check it's ours
	if (!(intrs & MI_INTR_AI))
	return IRQ_NONE;

	n64audio_write_reg(priv, AI_STATUS_REG, 1);

	if (priv->chan.substream && snd_pcm_running(priv->chan.substream)) {
	spin_lock_irqsave(&priv->chan.lock, flags);

	priv->chan.pos = priv->chan.nextpos;

	spin_unlock_irqrestore(&priv->chan.lock, flags);

	snd_pcm_period_elapsed(priv->chan.substream);
	if (priv->chan.substream && snd_pcm_running(priv->chan.substream))
	n64audio_push(priv);
	}

	return IRQ_HANDLED;
	}

	static const struct snd_pcm_hardware n64audio_pcm_hw = {
	.info = (SNDRV_PCM_INFO_MMAP \|
	SNDRV_PCM_INFO_MMAP_VALID \|
	SNDRV_PCM_INFO_INTERLEAVED \|
	SNDRV_PCM_INFO_BLOCK_TRANSFER),
	.formats = SNDRV_PCM_FMTBIT_S16_BE,
	.rates = SNDRV_PCM_RATE_8000_48000,
	.rate_min = 8000,
	.rate_max = 48000,
	.channels_min = 2,
	.channels_max = 2,
	.buffer_bytes_max = 32768,
	.period_bytes_min = 1024,
	.period_bytes_max = 32768,
	.periods_min = 3,
	// 3 periods lets the double-buffering hw read one buffer behind safely
	.periods_max = 128,
	};

	static int hw_rule_period_size(struct snd_pcm_hw_params *params,
	struct snd_pcm_hw_rule *rule)
	{
	struct snd_interval *c = hw_param_interval(params,
	SNDRV_PCM_HW_PARAM_PERIOD_SIZE);
	int changed = 0;

	/*
	* The DMA unit has errata on (start + len) & 0x3fff == 0x2000.
	* This constraint makes sure that the period size is not a power of two,
	* which combined with dma_alloc_coherent aligning the buffer to the largest
	* PoT <= size guarantees it won't be hit.
	*/

	if (is_power_of_2(c->min)) {
	c->min += 2;
	changed = 1;
	}
	if (is_power_of_2(c->max)) {
	c->max -= 2;
	changed = 1;
	}
	if (snd_interval_checkempty(c)) {
	c->empty = 1;
	return -EINVAL;
	}

	return changed;
	}

	static int n64audio_pcm_open(struct snd_pcm_substream *substream)
	{
	struct snd_pcm_runtime *runtime = substream->runtime;
	int err;

	runtime->hw = n64audio_pcm_hw;
	err = snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
	if (err < 0)
	return err;

	err = snd_pcm_hw_constraint_step(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 2);
	if (err < 0)
	return err;

	err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
	hw_rule_period_size, NULL, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, -1);
	if (err < 0)
	return err;

	return 0;
	}

	static int n64audio_pcm_prepare(struct snd_pcm_substream *substream)
	{
	struct snd_pcm_runtime *runtime = substream->runtime;
	struct n64audio *priv = substream->pcm->private_data;
	u32 rate;

	rate = ((2 * AI_NTSC_DACRATE / runtime->rate) + 1) / 2 - 1;

	n64audio_write_reg(priv, AI_RATE_REG, rate);

	rate /= 66;
	if (rate > 16)
	rate = 16;
	n64audio_write_reg(priv, AI_BITCLOCK_REG, rate - 1);

	spin_lock_irq(&priv->chan.lock);

	/* Setup the pseudo-dma transfer pointers. */
	priv->chan.pos = 0;
	priv->chan.nextpos = 0;
	priv->chan.substream = substream;
	priv->chan.writesize = snd_pcm_lib_period_bytes(substream);
	priv->chan.bufsize = snd_pcm_lib_buffer_bytes(substream);

	spin_unlock_irq(&priv->chan.lock);
	return 0;
	}

	static int n64audio_pcm_trigger(struct snd_pcm_substream *substream,
	int cmd)
	{
	struct n64audio *priv = substream->pcm->private_data;

	switch (cmd) {
	case SNDRV_PCM_TRIGGER_START:
	n64audio_push(substream->pcm->private_data);
	n64audio_write_reg(priv, AI_CONTROL_REG, 1);
	n64mi_write_reg(priv, MI_MASK_REG, MI_MASK_SET_AI);
	break;
	case SNDRV_PCM_TRIGGER_STOP:
	n64audio_write_reg(priv, AI_CONTROL_REG, 0);
	n64mi_write_reg(priv, MI_MASK_REG, MI_MASK_CLR_AI);
	break;
	default:
	return -EINVAL;
	}
	return 0;
	}

	static snd_pcm_uframes_t n64audio_pcm_pointer(struct snd_pcm_substream *substream)
	{
	struct n64audio *priv = substream->pcm->private_data;

	return bytes_to_frames(substream->runtime,
	priv->chan.pos);
	}

	static int n64audio_pcm_close(struct snd_pcm_substream *substream)
	{
	struct n64audio *priv = substream->pcm->private_data;

	priv->chan.substream = NULL;

	return 0;
	}

	static const struct snd_pcm_ops n64audio_pcm_ops = {
	.open = n64audio_pcm_open,
	.prepare = n64audio_pcm_prepare,
	.trigger = n64audio_pcm_trigger,
	.pointer = n64audio_pcm_pointer,
	.close = n64audio_pcm_close,
	};

	/*
	* The target device is embedded and RAM-constrained. We save RAM
	* by initializing in __init code that gets dropped late in boot.
	* For the same reason there is no module or unloading support.
	*/
	static int __init n64audio_probe(struct platform_device *pdev)
	{
	struct snd_card *card;
	struct snd_pcm *pcm;
	struct n64audio *priv;
	struct resource *res;
	int err;

	err = snd_card_new(&pdev->dev, SNDRV_DEFAULT_IDX1,
	SNDRV_DEFAULT_STR1,
	THIS_MODULE, sizeof(*priv), &card);
	if (err < 0)
	return err;

	priv = card->private_data;

	spin_lock_init(&priv->chan.lock);

	priv->card = card;

	priv->ring_base = dma_alloc_coherent(card->dev, 32 * 1024, &priv->ring_base_dma,
	GFP_DMA\|GFP_KERNEL);
	if (!priv->ring_base) {
	err = -ENOMEM;
	goto fail_card;
	}

	priv->mi_reg_base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(priv->mi_reg_base)) {
	err = PTR_ERR(priv->mi_reg_base);
	goto fail_dma_alloc;
	}

	priv->ai_reg_base = devm_platform_ioremap_resource(pdev, 1);
	if (IS_ERR(priv->ai_reg_base)) {
	err = PTR_ERR(priv->ai_reg_base);
	goto fail_dma_alloc;
	}

	err = snd_pcm_new(card, "N64 Audio", 0, 1, 0, &pcm);
	if (err < 0)
	goto fail_dma_alloc;

	pcm->private_data = priv;
	strcpy(pcm->name, "N64 Audio");

	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &n64audio_pcm_ops);
	snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_VMALLOC, card->dev, 0, 0);

	strcpy(card->driver, "N64 Audio");
	strcpy(card->shortname, "N64 Audio");
	strcpy(card->longname, "N64 Audio");

	res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
	if (devm_request_irq(&pdev->dev, res->start, n64audio_isr,
	IRQF_SHARED, "N64 Audio", priv)) {
	err = -EBUSY;
	goto fail_dma_alloc;
	}

	err = snd_card_register(card);
	if (err < 0)
	goto fail_dma_alloc;

	return 0;

	fail_dma_alloc:
	dma_free_coherent(card->dev, 32 * 1024, priv->ring_base, priv->ring_base_dma);

	fail_card:
	snd_card_free(card);
	return err;
	}

	static struct platform_driver n64audio_driver = {
	.driver = {
	.name = "n64audio",
	},
	};

	static int __init n64audio_init(void)
	{
	return platform_driver_probe(&n64audio_driver, n64audio_probe);
	}

	module_init(n64audio_init);