--- /dev/null
+// 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 (!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);
projects / linux-2.6-microblaze.git / commitdiff