brcm2708: update to latest version

As usual these patches were extracted from the raspberry pi repo:
https://github.com/raspberrypi/linux/commits/rpi-4.4.y

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

1 files changed, 90 insertions, 0 deletions

diff --git a/target/linux/brcm2708/patches-4.4/0133-bcm2835-interpolate-audio-delay.patch b/target/linux/brcm2708/patches-4.4/0133-bcm2835-interpolate-audio-delay.patch
new file mode 100644
index 0000000000..f08364bafe
--- /dev/null
+++ b/target/linux/brcm2708/patches-4.4/0133-bcm2835-interpolate-audio-delay.patch
@@ -0,0 +1,90 @@
+From 83eca613d0eddd2c8299f114b8fe573ccaffdefc Mon Sep 17 00:00:00 2001
+From: wm4 <wm4@nowhere>
+Date: Wed, 13 Jan 2016 19:44:47 +0100
+Subject: [PATCH 133/232] bcm2835: interpolate audio delay
+
+It appears the GPU only sends us a message all 10ms to update
+the playback progress. Other than this, the playback position
+(what SNDRV_PCM_IOCTL_DELAY will return) is not updated at all.
+Userspace will see jitter up to 10ms in the audio position.
+
+Make this a bit nicer for userspace by interpolating the
+position using the CPU clock.
+
+I'm not sure if setting snd_pcm_runtime.delay is the right
+approach for this. Or if there is maybe an already existing
+mechanism for position interpolation in the ALSA core.
+
+I only set SNDRV_PCM_INFO_BATCH because this appears to remove
+at least one situation snd_pcm_runtime.delay is used, so I have
+to worry less in which place I have to update this field, or
+how it interacts with the rest of ALSA.
+
+In the future, it might be nice to use VC_AUDIO_MSG_TYPE_LATENCY.
+One problem is that it requires sending a videocore message, and
+waiting for a reply, which could make the implementation much
+harder due to locking and synchronization requirements.
+---
+ sound/arm/bcm2835-pcm.c | 12 +++++++++++-
+ sound/arm/bcm2835.h     |  1 +
+ 2 files changed, 12 insertions(+), 1 deletion(-)
+
+--- a/sound/arm/bcm2835-pcm.c
++++ b/sound/arm/bcm2835-pcm.c
+@@ -25,7 +25,7 @@
+ /* hardware definition */
+ static struct snd_pcm_hardware snd_bcm2835_playback_hw = {
+ 	.info = (SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_BLOCK_TRANSFER |
+-		 SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID),
++		 SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID | SNDRV_PCM_INFO_BATCH),
+ 	.formats = SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S16_LE,
+ 	.rates = SNDRV_PCM_RATE_CONTINUOUS | SNDRV_PCM_RATE_8000_48000,
+ 	.rate_min = 8000,
+@@ -99,6 +99,8 @@ static irqreturn_t bcm2835_playback_fifo
+ 		alsa_stream->pos %= alsa_stream->buffer_size;
+ 	}
+ 
++	alsa_stream->interpolate_start = ktime_get_ns();
++
+ 	if (alsa_stream->substream) {
+ 		if (new_period)
+ 			snd_pcm_period_elapsed(alsa_stream->substream);
+@@ -399,6 +401,7 @@ static int snd_bcm2835_pcm_prepare(struc
+ 	alsa_stream->buffer_size = snd_pcm_lib_buffer_bytes(substream);
+ 	alsa_stream->period_size = snd_pcm_lib_period_bytes(substream);
+ 	alsa_stream->pos = 0;
++	alsa_stream->interpolate_start = ktime_get_ns();
+ 
+ 	audio_debug("buffer_size=%d, period_size=%d pos=%d frame_bits=%d\n",
+ 		      alsa_stream->buffer_size, alsa_stream->period_size,
+@@ -495,6 +498,7 @@ snd_bcm2835_pcm_pointer(struct snd_pcm_s
+ {
+ 	struct snd_pcm_runtime *runtime = substream->runtime;
+ 	bcm2835_alsa_stream_t *alsa_stream = runtime->private_data;
++	u64 now = ktime_get_ns();
+ 
+ 	audio_info(" .. IN\n");
+ 
+@@ -503,6 +507,12 @@ snd_bcm2835_pcm_pointer(struct snd_pcm_s
+ 		      frames_to_bytes(runtime, runtime->control->appl_ptr),
+ 		      alsa_stream->pos);
+ 
++	/* Give userspace better delay reporting by interpolating between GPU
++	 * notifications, assuming audio speed is close enough to the clock
++	 * used for ktime */
++	if (alsa_stream->interpolate_start && alsa_stream->interpolate_start < now)
++		runtime->delay = -(int)div_u64((now - alsa_stream->interpolate_start) * runtime->rate,  1000000000);
++
+ 	audio_info(" .. OUT\n");
+ 	return snd_pcm_indirect_playback_pointer(substream,
+ 						 &alsa_stream->pcm_indirect,
+--- a/sound/arm/bcm2835.h
++++ b/sound/arm/bcm2835.h
+@@ -137,6 +137,7 @@ typedef struct bcm2835_alsa_stream {
+ 	unsigned int pos;
+ 	unsigned int buffer_size;
+ 	unsigned int period_size;
++	u64 interpolate_start;
+ 
+ 	uint32_t enable_fifo_irq;
+ 	irq_handler_t fifo_irq_handler;