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sound: Add n64 driver
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This adds support for the Nintendo 64 console's sound.

Signed-off-by: Lauri Kasanen <[email protected]>
Reviewed-by: Takashi Iwai <[email protected]>
Signed-off-by: Thomas Bogendoerfer <[email protected]>
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@clbr @tsbogend
clbr authored and tsbogend committed Jan 25, 2021
1 parent 42b2099 commit 1448f8a
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7 changes: 7 additions & 0 deletions sound/mips/Kconfig
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Expand Up @@ -24,5 +24,12 @@ config SND_SGI_HAL2
help
Sound support for the SGI Indy and Indigo2 Workstation.

config SND_N64
bool "N64 Audio"
depends on MACH_NINTENDO64 && SND=y
select SND_PCM
help
Sound support for the N64.

endif # SND_MIPS

1 change: 1 addition & 0 deletions sound/mips/Makefile
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Expand Up @@ -9,3 +9,4 @@ snd-sgi-hal2-objs := hal2.o
# Toplevel Module Dependency
obj-$(CONFIG_SND_SGI_O2) += snd-sgi-o2.o
obj-$(CONFIG_SND_SGI_HAL2) += snd-sgi-hal2.o
obj-$(CONFIG_SND_N64) += snd-n64.o
372 changes: 372 additions & 0 deletions sound/mips/snd-n64.c
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@@ -0,0 +1,372 @@
// 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 <[email protected]>");
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 (!priv->mi_reg_base) {
err = -EINVAL;
goto fail_dma_alloc;
}

priv->ai_reg_base = devm_platform_ioremap_resource(pdev, 1);
if (!priv->ai_reg_base) {
err = -EINVAL;
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);

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