Re: [PATCH v2 1/9] drm: bridge/dw_hdmi-ahb-audio: add audio driver

[Russell King]

Add ALSA based HDMI AHB audio driver for dw_hdmi.  The only buffer
format supported by the hardware is its own special IEC958 based format,
which is not compatible with any ALSA format.  To avoid doing too much
data manipulation within the driver, we support only ALSAs IEC958 LE and
24-bit PCM formats for 2 to 6 channels, which we convert to its hardware
format.

A more desirable solution would be to have this conversion in userspace,
but ALSA does not appear to allow such transformations outside of
libasound itself.

Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
---
v2: updated with Takashi Iwai's comments... and with a fixed Cc: line.

 drivers/gpu/drm/bridge/Kconfig             |  10 +
 drivers/gpu/drm/bridge/Makefile            |   1 +
 drivers/gpu/drm/bridge/dw_hdmi-ahb-audio.c | 579 +++++++++++++++++++++++++++++
 drivers/gpu/drm/bridge/dw_hdmi-audio.h     |  13 +
 drivers/gpu/drm/bridge/dw_hdmi.c           |  24 ++
 drivers/gpu/drm/bridge/dw_hdmi.h           |   3 +
 6 files changed, 630 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/dw_hdmi-ahb-audio.c
 create mode 100644 drivers/gpu/drm/bridge/dw_hdmi-audio.h

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index acef3223772c..56ed35fe0734 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -3,6 +3,16 @@ config DRM_DW_HDMI
 	depends on DRM
 	select DRM_KMS_HELPER
 
+config DRM_DW_HDMI_AHB_AUDIO
+	tristate "Synopsis Designware AHB Audio interface"
+	depends on DRM_DW_HDMI && SND
+	select SND_PCM
+	select SND_PCM_IEC958
+	help
+	  Support the AHB Audio interface which is part of the Synopsis
+	  Designware HDMI block.  This is used in conjunction with
+	  the i.MX6 HDMI driver.
+
 config DRM_PTN3460
 	tristate "PTN3460 DP/LVDS bridge"
 	depends on DRM
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index 8dfebd984370..eb80dbbb8365 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -3,3 +3,4 @@ ccflags-y := -Iinclude/drm
 obj-$(CONFIG_DRM_PS8622) += ps8622.o
 obj-$(CONFIG_DRM_PTN3460) += ptn3460.o
 obj-$(CONFIG_DRM_DW_HDMI) += dw_hdmi.o
+obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw_hdmi-ahb-audio.o
diff --git a/drivers/gpu/drm/bridge/dw_hdmi-ahb-audio.c b/drivers/gpu/drm/bridge/dw_hdmi-ahb-audio.c
new file mode 100644
index 000000000000..bf379310008a
--- /dev/null
+++ b/drivers/gpu/drm/bridge/dw_hdmi-ahb-audio.c
@@ -0,0 +1,579 @@
+/*
+ * DesignWare HDMI audio driver
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Written and tested against the Designware HDMI Tx found in iMX6.
+ */
+#include <linux/io.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <drm/bridge/dw_hdmi.h>
+
+#include <sound/asoundef.h>
+#include <sound/core.h>
+#include <sound/initval.h>
+#include <sound/pcm.h>
+#include <sound/pcm_iec958.h>
+
+#include "dw_hdmi-audio.h"
+
+#define DRIVER_NAME "dw-hdmi-ahb-audio"
+
+/* Provide some bits rather than bit offsets */
+enum {
+	HDMI_AHB_DMA_CONF0_SW_FIFO_RST = BIT(7),
+	HDMI_AHB_DMA_CONF0_EN_HLOCK = BIT(3),
+	HDMI_AHB_DMA_START_START = BIT(0),
+	HDMI_AHB_DMA_STOP_STOP = BIT(0),
+	HDMI_IH_MUTE_AHBDMAAUD_STAT0_ERROR = BIT(5),
+	HDMI_IH_MUTE_AHBDMAAUD_STAT0_LOST = BIT(4),
+	HDMI_IH_MUTE_AHBDMAAUD_STAT0_RETRY = BIT(3),
+	HDMI_IH_MUTE_AHBDMAAUD_STAT0_DONE = BIT(2),
+	HDMI_IH_MUTE_AHBDMAAUD_STAT0_BUFFFULL = BIT(1),
+	HDMI_IH_MUTE_AHBDMAAUD_STAT0_BUFFEMPTY = BIT(0),
+	HDMI_IH_MUTE_AHBDMAAUD_STAT0_ALL =
+		HDMI_IH_MUTE_AHBDMAAUD_STAT0_ERROR |
+		HDMI_IH_MUTE_AHBDMAAUD_STAT0_LOST |
+		HDMI_IH_MUTE_AHBDMAAUD_STAT0_RETRY |
+		HDMI_IH_MUTE_AHBDMAAUD_STAT0_DONE |
+		HDMI_IH_MUTE_AHBDMAAUD_STAT0_BUFFFULL |
+		HDMI_IH_MUTE_AHBDMAAUD_STAT0_BUFFEMPTY,
+	HDMI_IH_AHBDMAAUD_STAT0_ERROR = BIT(5),
+	HDMI_IH_AHBDMAAUD_STAT0_LOST = BIT(4),
+	HDMI_IH_AHBDMAAUD_STAT0_RETRY = BIT(3),
+	HDMI_IH_AHBDMAAUD_STAT0_DONE = BIT(2),
+	HDMI_IH_AHBDMAAUD_STAT0_BUFFFULL = BIT(1),
+	HDMI_IH_AHBDMAAUD_STAT0_BUFFEMPTY = BIT(0),
+	HDMI_IH_AHBDMAAUD_STAT0_ALL =
+		HDMI_IH_AHBDMAAUD_STAT0_ERROR |
+		HDMI_IH_AHBDMAAUD_STAT0_LOST |
+		HDMI_IH_AHBDMAAUD_STAT0_RETRY |
+		HDMI_IH_AHBDMAAUD_STAT0_DONE |
+		HDMI_IH_AHBDMAAUD_STAT0_BUFFFULL |
+		HDMI_IH_AHBDMAAUD_STAT0_BUFFEMPTY,
+	HDMI_AHB_DMA_CONF0_INCR16 = 2 << 1,
+	HDMI_AHB_DMA_CONF0_INCR8 = 1 << 1,
+	HDMI_AHB_DMA_CONF0_INCR4 = 0,
+	HDMI_AHB_DMA_CONF0_BURST_MODE = BIT(0),
+	HDMI_AHB_DMA_MASK_DONE = BIT(7),
+	HDMI_REVISION_ID = 0x0001,
+	HDMI_IH_AHBDMAAUD_STAT0 = 0x0109,
+	HDMI_IH_MUTE_AHBDMAAUD_STAT0 = 0x0189,
+	HDMI_AHB_DMA_CONF0 = 0x3600,
+	HDMI_AHB_DMA_START = 0x3601,
+	HDMI_AHB_DMA_STOP = 0x3602,
+	HDMI_AHB_DMA_THRSLD = 0x3603,
+	HDMI_AHB_DMA_STRADDR0 = 0x3604,
+	HDMI_AHB_DMA_STPADDR0 = 0x3608,
+	HDMI_AHB_DMA_MASK = 0x3614,
+	HDMI_AHB_DMA_POL = 0x3615,
+	HDMI_AHB_DMA_CONF1 = 0x3616,
+	HDMI_AHB_DMA_BUFFPOL = 0x361a,
+};
+
+struct snd_dw_hdmi {
+	struct snd_card *card;
+	struct snd_pcm *pcm;
+	spinlock_t lock;
+	struct dw_hdmi_audio_data data;
+	struct snd_pcm_substream *substream;
+	void (*reformat)(struct snd_dw_hdmi *, size_t, size_t);
+	void *buf_src;
+	void *buf_dst;
+	dma_addr_t buf_addr;
+	unsigned buf_offset;
+	unsigned buf_period;
+	unsigned buf_size;
+	unsigned channels;
+	u8 revision;
+	u8 iec_offset;
+	u8 cs[192][8];
+};
+
+static void dw_hdmi_writel(u32 val, void __iomem *ptr)
+{
+	writeb_relaxed(val, ptr);
+	writeb_relaxed(val >> 8, ptr + 1);
+	writeb_relaxed(val >> 16, ptr + 2);
+	writeb_relaxed(val >> 24, ptr + 3);
+}
+
+/*
+ * Convert to hardware format: The userspace buffer contains IEC958 samples,
+ * with the PCUV bits in bits 31..28 and audio samples in bits 27..4.  We
+ * need these to be in bits 27..24, with the IEC B bit in bit 28, and audio
+ * samples in 23..0.
+ *
+ * Default preamble in bits 3..0: 8 = block start, 4 = even 2 = odd
+ *
+ * Ideally, we could do with having the data properly formatted in userspace.
+ */
+static void dw_hdmi_reformat_iec958(struct snd_dw_hdmi *dw,
+	size_t offset, size_t bytes)
+{
+	u32 *src = dw->buf_src + offset;
+	u32 *dst = dw->buf_dst + offset;
+	u32 *end = dw->buf_src + offset + bytes;
+
+	do {
+		u32 b, sample = *src++;
+
+		b = (sample & 8) << (28 - 3);
+
+		sample >>= 4;
+
+		*dst++ = sample | b;
+	} while (src < end);
+}
+
+static u32 parity(u32 sample)
+{
+	sample ^= sample >> 16;
+	sample ^= sample >> 8;
+	sample ^= sample >> 4;
+	sample ^= sample >> 2;
+	sample ^= sample >> 1;
+	return (sample & 1) << 27;
+}
+
+static void dw_hdmi_reformat_s24(struct snd_dw_hdmi *dw,
+	size_t offset, size_t bytes)
+{
+	u32 *src = dw->buf_src + offset;
+	u32 *dst = dw->buf_dst + offset;
+	u32 *end = dw->buf_src + offset + bytes;
+
+	do {
+		unsigned i;
+		u8 *cs;
+
+		cs = dw->cs[dw->iec_offset++];
+		if (dw->iec_offset >= 192)
+			dw->iec_offset = 0;
+
+		i = dw->channels;
+		do {
+			u32 sample = *src++;
+
+			sample &= ~0xff000000;
+			sample |= *cs++ << 24;
+			sample |= parity(sample & ~0xf8000000);
+
+			*dst++ = sample;
+		} while (--i);
+	} while (src < end);
+}
+
+static void dw_hdmi_create_cs(struct snd_dw_hdmi *dw,
+	struct snd_pcm_runtime *runtime)
+{
+	u8 cs[4];
+	unsigned ch, i, j;
+
+	snd_pcm_create_iec958_consumer(runtime, cs, sizeof(cs));
+
+	memset(dw->cs, 0, sizeof(dw->cs));
+
+	for (ch = 0; ch < 8; ch++) {
+		cs[2] &= ~IEC958_AES2_CON_CHANNEL;
+		cs[2] |= (ch + 1) << 4;
+
+		for (i = 0; i < ARRAY_SIZE(cs); i++) {
+			unsigned c = cs[i];
+
+			for (j = 0; j < 8; j++, c >>= 1)
+				dw->cs[i * 8 + j][ch] = (c & 1) << 2;
+		}
+	}
+	dw->cs[0][0] |= BIT(4);
+}
+
+static void dw_hdmi_start_dma(struct snd_dw_hdmi *dw)
+{
+	void __iomem *base = dw->data.base;
+	unsigned offset = dw->buf_offset;
+	unsigned period = dw->buf_period;
+	u32 start, stop;
+
+	dw->reformat(dw, offset, period);
+
+	/* Clear all irqs before enabling irqs and starting DMA */
+	writeb_relaxed(HDMI_IH_AHBDMAAUD_STAT0_ALL,
+		       base + HDMI_IH_AHBDMAAUD_STAT0);
+
+	start = dw->buf_addr + offset;
+	stop = start + period - 1;
+
+	/* Setup the hardware start/stop addresses */
+	dw_hdmi_writel(start, base + HDMI_AHB_DMA_STRADDR0);
+	dw_hdmi_writel(stop, base + HDMI_AHB_DMA_STPADDR0);
+
+	writeb_relaxed((u8)~HDMI_AHB_DMA_MASK_DONE, base + HDMI_AHB_DMA_MASK);
+	writeb(HDMI_AHB_DMA_START_START, base + HDMI_AHB_DMA_START);
+
+	offset += period;
+	if (offset >= dw->buf_size)
+		offset = 0;
+	dw->buf_offset = offset;
+}
+
+static void dw_hdmi_stop_dma(struct snd_dw_hdmi *dw)
+{
+	/* Disable interrupts before disabling DMA */
+	writeb_relaxed(~0, dw->data.base + HDMI_AHB_DMA_MASK);
+	writeb_relaxed(HDMI_AHB_DMA_STOP_STOP, dw->data.base + HDMI_AHB_DMA_STOP);
+}
+
+static irqreturn_t snd_dw_hdmi_irq(int irq, void *data)
+{
+	struct snd_dw_hdmi *dw = data;
+	struct snd_pcm_substream *substream;
+	unsigned stat;
+
+	stat = readb_relaxed(dw->data.base + HDMI_IH_AHBDMAAUD_STAT0);
+	if (!stat)
+		return IRQ_NONE;
+
+	writeb_relaxed(stat, dw->data.base + HDMI_IH_AHBDMAAUD_STAT0);
+
+	substream = dw->substream;
+	if (stat & HDMI_IH_AHBDMAAUD_STAT0_DONE && substream) {
+		snd_pcm_period_elapsed(substream);
+
+		spin_lock(&dw->lock);
+		if (dw->substream)
+			dw_hdmi_start_dma(dw);
+		spin_unlock(&dw->lock);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static struct snd_pcm_hardware dw_hdmi_hw = {
+	.info = SNDRV_PCM_INFO_INTERLEAVED |
+		SNDRV_PCM_INFO_BLOCK_TRANSFER |
+		SNDRV_PCM_INFO_MMAP |
+		SNDRV_PCM_INFO_MMAP_VALID,
+	.formats = SNDRV_PCM_FMTBIT_IEC958_SUBFRAME_LE |
+		   SNDRV_PCM_FMTBIT_S24_LE,
+	.rates = SNDRV_PCM_RATE_32000 |
+		 SNDRV_PCM_RATE_44100 |
+		 SNDRV_PCM_RATE_48000 |
+		 SNDRV_PCM_RATE_88200 |
+		 SNDRV_PCM_RATE_96000 |
+		 SNDRV_PCM_RATE_176400 |
+		 SNDRV_PCM_RATE_192000,
+	.channels_min = 2,
+	.channels_max = 8,
+	.buffer_bytes_max = 64 * 1024,
+	.period_bytes_min = 256,
+	.period_bytes_max = 8192,	/* ERR004323: must limit to 8k */
+	.periods_min = 2,
+	.periods_max = 16,
+	.fifo_size = 0,
+};
+
+static int dw_hdmi_open(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct snd_dw_hdmi *dw = substream->private_data;
+	void __iomem *base = dw->data.base;
+	int ret;
+
+	runtime->hw = dw_hdmi_hw;
+
+	ret = snd_pcm_limit_hw_rates(runtime);
+	if (ret < 0)
+		return ret;
+
+	ret = snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
+	if (ret < 0)
+		return ret;
+
+	/* Clear FIFO */
+	writeb_relaxed(HDMI_AHB_DMA_CONF0_SW_FIFO_RST,
+		       base + HDMI_AHB_DMA_CONF0);
+
+	/* Configure interrupt polarities */
+	writeb_relaxed(~0, base + HDMI_AHB_DMA_POL);
+	writeb_relaxed(~0, base + HDMI_AHB_DMA_BUFFPOL);
+
+	/* Keep interrupts masked, and clear any pending */
+	writeb_relaxed(~0, base + HDMI_AHB_DMA_MASK);
+	writeb_relaxed(~0, base + HDMI_IH_AHBDMAAUD_STAT0);
+
+	ret = request_irq(dw->data.irq, snd_dw_hdmi_irq, IRQF_SHARED,
+			  "dw-hdmi-audio", dw);
+	if (ret)
+		return ret;
+
+	/* Un-mute done interrupt */
+	writeb_relaxed(HDMI_IH_MUTE_AHBDMAAUD_STAT0_ALL &
+		       ~HDMI_IH_MUTE_AHBDMAAUD_STAT0_DONE,
+		       base + HDMI_IH_MUTE_AHBDMAAUD_STAT0);
+
+	return 0;
+}
+
+static int dw_hdmi_close(struct snd_pcm_substream *substream)
+{
+	struct snd_dw_hdmi *dw = substream->private_data;
+
+	/* Mute all interrupts */
+	writeb_relaxed(HDMI_IH_MUTE_AHBDMAAUD_STAT0_ALL,
+		       dw->data.base + HDMI_IH_MUTE_AHBDMAAUD_STAT0);
+
+	free_irq(dw->data.irq, dw);
+
+	return 0;
+}
+
+static int dw_hdmi_hw_free(struct snd_pcm_substream *substream)
+{
+	return snd_pcm_lib_free_vmalloc_buffer(substream);
+}
+
+static int dw_hdmi_hw_params(struct snd_pcm_substream *substream,
+	struct snd_pcm_hw_params *params)
+{
+	return snd_pcm_lib_alloc_vmalloc_buffer(substream,
+						params_buffer_bytes(params));
+}
+
+static int dw_hdmi_prepare(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct snd_dw_hdmi *dw = substream->private_data;
+	u8 threshold, conf0, conf1;
+
+	/* Setup as per 3.0.5 FSL 4.1.0 BSP */
+	switch (dw->revision) {
+	case 0x0a:
+		conf0 = HDMI_AHB_DMA_CONF0_BURST_MODE |
+			HDMI_AHB_DMA_CONF0_INCR4;
+		if (runtime->channels == 2)
+			threshold = 126;
+		else
+			threshold = 124;
+		break;
+	case 0x1a:
+		conf0 = HDMI_AHB_DMA_CONF0_BURST_MODE |
+			HDMI_AHB_DMA_CONF0_INCR8;
+		threshold = 128;
+		break;
+	default:
+		/* NOTREACHED */
+		return -EINVAL;
+	}
+
+	dw_hdmi_set_sample_rate(dw->data.hdmi, runtime->rate);
+
+	/* Minimum number of bytes in the fifo. */
+	runtime->hw.fifo_size = threshold * 32;
+
+	conf0 |= HDMI_AHB_DMA_CONF0_EN_HLOCK;
+	conf1 = (1 << runtime->channels) - 1;
+
+	writeb_relaxed(threshold, dw->data.base + HDMI_AHB_DMA_THRSLD);
+	writeb_relaxed(conf0, dw->data.base + HDMI_AHB_DMA_CONF0);
+	writeb_relaxed(conf1, dw->data.base + HDMI_AHB_DMA_CONF1);
+
+	switch (runtime->format) {
+	case SNDRV_PCM_FORMAT_IEC958_SUBFRAME_LE:
+		dw->reformat = dw_hdmi_reformat_iec958;
+		break;
+	case SNDRV_PCM_FORMAT_S24_LE:
+		dw_hdmi_create_cs(dw, runtime);
+		dw->reformat = dw_hdmi_reformat_s24;
+		break;
+	}
+	dw->iec_offset = 0;
+	dw->channels = runtime->channels;
+	dw->buf_src  = runtime->dma_area;
+	dw->buf_dst  = substream->dma_buffer.area;
+	dw->buf_addr = substream->dma_buffer.addr;
+	dw->buf_period = snd_pcm_lib_period_bytes(substream);
+	dw->buf_size = snd_pcm_lib_buffer_bytes(substream);
+
+	return 0;
+}
+
+static int dw_hdmi_trigger(struct snd_pcm_substream *substream, int cmd)
+{
+	struct snd_dw_hdmi *dw = substream->private_data;
+	unsigned long flags;
+	int ret = 0;
+
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_START:
+		spin_lock_irqsave(&dw->lock, flags);
+		dw->buf_offset = 0;
+		dw->substream = substream;
+		dw_hdmi_start_dma(dw);
+		dw_hdmi_audio_enable(dw->data.hdmi);
+		spin_unlock_irqrestore(&dw->lock, flags);
+		substream->runtime->delay = substream->runtime->period_size;
+		break;
+
+	case SNDRV_PCM_TRIGGER_STOP:
+		spin_lock_irqsave(&dw->lock, flags);
+		dw->substream = NULL;
+		dw_hdmi_stop_dma(dw);
+		dw_hdmi_audio_disable(dw->data.hdmi);
+		spin_unlock_irqrestore(&dw->lock, flags);
+		break;
+
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+static snd_pcm_uframes_t dw_hdmi_pointer(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct snd_dw_hdmi *dw = substream->private_data;
+
+	/*
+	 * We are unable to report the exact hardware position as
+	 * reading the 32-bit DMA position using 8-bit reads is racy.
+	 */
+	return bytes_to_frames(runtime, dw->buf_offset);
+}
+
+static struct snd_pcm_ops snd_dw_hdmi_ops = {
+	.open = dw_hdmi_open,
+	.close = dw_hdmi_close,
+	.ioctl = snd_pcm_lib_ioctl,
+	.hw_params = dw_hdmi_hw_params,
+	.hw_free = dw_hdmi_hw_free,
+	.prepare = dw_hdmi_prepare,
+	.trigger = dw_hdmi_trigger,
+	.pointer = dw_hdmi_pointer,
+	.page = snd_pcm_lib_get_vmalloc_page,
+};
+
+static int snd_dw_hdmi_probe(struct platform_device *pdev)
+{
+	const struct dw_hdmi_audio_data *data = pdev->dev.platform_data;
+	struct device *dev = pdev->dev.parent;
+	struct snd_dw_hdmi *dw;
+	struct snd_card *card;
+	struct snd_pcm *pcm;
+	unsigned revision;
+	int ret;
+
+	writeb_relaxed(HDMI_IH_MUTE_AHBDMAAUD_STAT0_ALL,
+		       data->base + HDMI_IH_MUTE_AHBDMAAUD_STAT0);
+	revision = readb_relaxed(data->base + HDMI_REVISION_ID);
+	if (revision != 0x0a && revision != 0x1a) {
+		dev_err(dev, "dw-hdmi-audio: unknown revision 0x%02x\n",
+			revision);
+		return -ENXIO;
+	}
+
+	ret = snd_card_new(dev, SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1,
+			      THIS_MODULE, sizeof(struct snd_dw_hdmi), &card);
+	if (ret < 0)
+		return ret;
+
+	strlcpy(card->driver, DRIVER_NAME, sizeof(card->driver));
+	strlcpy(card->shortname, "DW-HDMI", sizeof(card->shortname));
+	snprintf(card->longname, sizeof(card->longname),
+		 "%s rev 0x%02x, irq %d", card->shortname, revision,
+		 data->irq);
+
+	dw = card->private_data;
+	dw->card = card;
+	dw->data = *data;
+	dw->revision = revision;
+
+	spin_lock_init(&dw->lock);
+
+	ret = snd_pcm_new(card, "DW HDMI", 0, 1, 0, &pcm);
+	if (ret < 0)
+		goto err;
+
+	dw->pcm = pcm;
+	pcm->private_data = dw;
+	strlcpy(pcm->name, DRIVER_NAME, sizeof(pcm->name));
+	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &snd_dw_hdmi_ops);
+
+	snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,
+			dev, 64 * 1024, 64 * 1024);
+
+	ret = snd_card_register(card);
+	if (ret < 0)
+		goto err;
+
+	platform_set_drvdata(pdev, dw);
+
+	return 0;
+
+err:
+	snd_card_free(card);
+	return ret;
+}
+
+static int snd_dw_hdmi_remove(struct platform_device *pdev)
+{
+	struct snd_dw_hdmi *dw = platform_get_drvdata(pdev);
+
+	snd_card_free(dw->card);
+
+	return 0;
+}
+
+#if defined(CONFIG_PM_SLEEP) && defined(IS_NOT_BROKEN)
+/*
+ * This code is fine, but requires implementation in the dw_hdmi_trigger()
+ * method which is currently missing as I have no way to test this.
+ */
+static int snd_dw_hdmi_suspend(struct device *dev)
+{
+	struct snd_dw_hdmi *dw = dev_get_drvdata(dev);
+
+	snd_power_change_state(dw->card, SNDRV_CTL_POWER_D3cold);
+	snd_pcm_suspend_all(dw->pcm);
+
+	return 0;
+}
+
+static int snd_dw_hdmi_resume(struct device *dev)
+{
+	struct snd_dw_hdmi *dw = dev_get_drvdata(dev);
+
+	snd_power_change_state(dw->card, SNDRV_CTL_POWER_D0);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(snd_dw_hdmi_pm, snd_dw_hdmi_suspend,
+			 snd_dw_hdmi_resume);
+#define PM_OPS &snd_dw_hdmi_pm
+#else
+#define PM_OPS NULL
+#endif
+
+static struct platform_driver snd_dw_hdmi_driver = {
+	.probe	= snd_dw_hdmi_probe,
+	.remove	= snd_dw_hdmi_remove,
+	.driver	= {
+		.name = DRIVER_NAME,
+		.owner = THIS_MODULE,
+		.pm = PM_OPS,
+	},
+};
+
+module_platform_driver(snd_dw_hdmi_driver);
+
+MODULE_AUTHOR("Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Synopsis Designware HDMI AHB ALSA interface");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" DRIVER_NAME);
diff --git a/drivers/gpu/drm/bridge/dw_hdmi-audio.h b/drivers/gpu/drm/bridge/dw_hdmi-audio.h
new file mode 100644
index 000000000000..1e840118d90a
--- /dev/null
+++ b/drivers/gpu/drm/bridge/dw_hdmi-audio.h
@@ -0,0 +1,13 @@
+#ifndef DW_HDMI_AUDIO_H
+#define DW_HDMI_AUDIO_H
+
+struct dw_hdmi;
+
+struct dw_hdmi_audio_data {
+	phys_addr_t phys;
+	void __iomem *base;
+	int irq;
+	struct dw_hdmi *hdmi;
+};
+
+#endif
diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
index fba25607ef88..b65464789fbd 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -28,6 +28,7 @@
 #include <drm/bridge/dw_hdmi.h>
 
 #include "dw_hdmi.h"
+#include "dw_hdmi-audio.h"
 
 #define HDMI_EDID_LEN		512
 
@@ -104,6 +105,7 @@ struct dw_hdmi {
 	struct drm_encoder *encoder;
 	struct drm_bridge *bridge;
 
+	struct platform_device *audio;
 	enum dw_hdmi_devtype dev_type;
 	struct device *dev;
 	struct clk *isfr_clk;
@@ -1732,7 +1734,9 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
 {
 	struct drm_device *drm = data;
 	struct device_node *np = dev->of_node;
+	struct platform_device_info pdevinfo;
 	struct device_node *ddc_node;
+	struct dw_hdmi_audio_data audio;
 	struct dw_hdmi *hdmi;
 	int ret;
 	u32 val = 1;
@@ -1860,6 +1864,23 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
 	hdmi_writeb(hdmi, ~(HDMI_IH_PHY_STAT0_HPD | HDMI_IH_PHY_STAT0_RX_SENSE),
 		    HDMI_IH_MUTE_PHY_STAT0);
 
+	memset(&pdevinfo, 0, sizeof(pdevinfo));
+	pdevinfo.parent = dev;
+	pdevinfo.id = PLATFORM_DEVID_AUTO;
+
+	if (hdmi_readb(hdmi, HDMI_CONFIG1_ID) & HDMI_CONFIG1_AHB) {
+		audio.phys = iores->start;
+		audio.base = hdmi->regs;
+		audio.irq = irq;
+		audio.hdmi = hdmi;
+
+		pdevinfo.name = "dw-hdmi-ahb-audio";
+		pdevinfo.data = &audio;
+		pdevinfo.size_data = sizeof(audio);
+		pdevinfo.dma_mask = DMA_BIT_MASK(32);
+		hdmi->audio = platform_device_register_full(&pdevinfo);
+	}
+
 	dev_set_drvdata(dev, hdmi);
 
 	return 0;
@@ -1877,6 +1898,9 @@ void dw_hdmi_unbind(struct device *dev, struct device *master, void *data)
 {
 	struct dw_hdmi *hdmi = dev_get_drvdata(dev);
 
+	if (hdmi->audio && !IS_ERR(hdmi->audio))
+		platform_device_unregister(hdmi->audio);
+
 	/* Disable all interrupts */
 	hdmi_writeb(hdmi, ~0, HDMI_IH_MUTE_PHY_STAT0);
 
diff --git a/drivers/gpu/drm/bridge/dw_hdmi.h b/drivers/gpu/drm/bridge/dw_hdmi.h
index 175dbc89a824..78e54e813212 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.h
+++ b/drivers/gpu/drm/bridge/dw_hdmi.h
@@ -545,6 +545,9 @@
 #define HDMI_I2CM_FS_SCL_LCNT_0_ADDR            0x7E12
 
 enum {
+/* CONFIG1_ID field values */
+	HDMI_CONFIG1_AHB = 0x01,
+
 /* IH_FC_INT2 field values */
 	HDMI_IH_FC_INT2_OVERFLOW_MASK = 0x03,
 	HDMI_IH_FC_INT2_LOW_PRIORITY_OVERFLOW = 0x02,
-- 
2.1.0

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