From: Stefan Wahren <stefan.wahren@i2se.com>
To: Takashi Iwai <tiwai@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Eric Anholt <eric@anholt.net>,
linux-rpi-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Phil Elwell <phil@raspberrypi.org>
Subject: Re: [PATCH 17/29] staging: bcm2835-audio: Add 10ms period constraint
Date: Wed, 19 Sep 2018 11:42:22 +0200 [thread overview]
Message-ID: <4c5f9aed-8fbe-fe22-0c8d-097d8915805c@i2se.com> (raw)
In-Reply-To: <20180904155858.8001-18-tiwai@suse.de>
Hi Takashi,
Am 04.09.2018 um 17:58 schrieb Takashi Iwai:
> It seems that the resolution of vc04 callback is in 10 msec; i.e. the
> minimal period size is also 10 msec.
>
> This patch adds the corresponding hw constraint.
>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
> drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c
> index 9659c25b9f9d..6d89db6e14e4 100644
> --- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c
> +++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c
> @@ -145,6 +145,11 @@ static int snd_bcm2835_playback_open_generic(
> SNDRV_PCM_HW_PARAM_PERIOD_BYTES,
> 16);
>
> + /* position update is in 10ms order */
> + snd_pcm_hw_constraint_minmax(runtime,
> + SNDRV_PCM_HW_PARAM_PERIOD_TIME,
> + 10 * 1000, UINT_MAX);
> +
> chip->alsa_stream[idx] = alsa_stream;
>
> chip->opened |= (1 << idx);
in the Foundation Kernel (Downstream) there is a patch to interpolate
the audio delay. So my questions is, does your patch above makes the
following patch obsolete?
[PATCH] 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.
---
.../vc04_services/bcm2835-audio/bcm2835-pcm.c | 13 +++++++++++--
.../staging/vc04_services/bcm2835-audio/bcm2835.h | 1 +
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c
index 94654c0c7bba5..36165a60fb059 100644
--- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c
+++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c
@@ -22,7 +22,7 @@
/* hardware definition */
static const 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,
@@ -93,6 +93,8 @@ void bcm2835_playback_fifo(struct bcm2835_alsa_stream *alsa_stream)
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);
@@ -323,6 +325,7 @@ static int snd_bcm2835_pcm_prepare(struct snd_pcm_substream *substream)
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,
@@ -415,13 +418,19 @@ snd_bcm2835_pcm_pointer(struct snd_pcm_substream *substream)
{
struct snd_pcm_runtime *runtime = substream->runtime;
struct bcm2835_alsa_stream *alsa_stream = runtime->private_data;
-
+ u64 now = ktime_get_ns();
audio_debug("pcm_pointer... (%d) hwptr=%d appl=%d pos=%d\n", 0,
frames_to_bytes(runtime, runtime->status->hw_ptr),
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);
+
return snd_pcm_indirect_playback_pointer(substream,
&alsa_stream->pcm_indirect,
alsa_stream->pos);
diff --git a/drivers/staging/vc04_services/bcm2835-audio/bcm2835.h b/drivers/staging/vc04_services/bcm2835-audio/bcm2835.h
index 379604d3554e8..e64862e1781be 100644
--- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835.h
+++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835.h
@@ -137,6 +137,7 @@ struct bcm2835_alsa_stream {
unsigned int pos;
unsigned int buffer_size;
unsigned int period_size;
+ u64 interpolate_start;
atomic_t retrieved;
struct bcm2835_audio_instance *instance;
next prev parent reply other threads:[~2018-09-19 9:42 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-04 15:58 [PATCH 00/29] staging: bcm2835-audio: Cleanups and fixes Takashi Iwai
2018-09-04 15:58 ` [PATCH 01/29] staging: bcm2835-audio: Clean up mutex locks Takashi Iwai
2018-09-04 15:58 ` [PATCH 02/29] staging: bcm2835-audio: Remove redundant spdif stream ctls Takashi Iwai
2018-09-04 15:58 ` [PATCH 03/29] staging: bcm2835-audio: Clean up include files in bcm2835-ctl.c Takashi Iwai
2018-09-08 13:25 ` Stefan Wahren
2018-09-08 16:21 ` Takashi Iwai
2018-09-04 15:58 ` [PATCH 04/29] staging: bcm2835-audio: Remove redundant substream mask checks Takashi Iwai
2018-09-04 15:58 ` [PATCH 05/29] staging: bcm2835-audio: Fix mute controls, volume handling cleanup Takashi Iwai
2018-09-04 15:58 ` [PATCH 06/29] staging: bcm2835-audio: Remove redundant function calls Takashi Iwai
2018-09-04 15:58 ` [PATCH 07/29] staging: bcm2835-audio: Remove superfluous open flag Takashi Iwai
2018-09-04 15:58 ` [PATCH 08/29] staging: bcm2835-audio: Drop useless running flag and check Takashi Iwai
2018-09-04 15:58 ` [PATCH 09/29] staging: bcm2835-audio: Fix incorrect draining handling Takashi Iwai
2018-09-04 15:58 ` [PATCH 10/29] staging: bcm2835-audio: Kill unused spinlock Takashi Iwai
2018-09-04 15:58 ` [PATCH 11/29] staging: bcm2835-audio: Use PCM runtime values instead Takashi Iwai
2018-09-04 15:58 ` [PATCH 12/29] staging: bcm2835-audio: Drop unnecessary pcm indirect setup Takashi Iwai
2018-09-04 15:58 ` [PATCH 13/29] staging: bcm2835-audio: Drop useless NULL check Takashi Iwai
2018-09-04 15:58 ` [PATCH 14/29] staging: bcm2835-audio: Propagate parameter setup error Takashi Iwai
2018-09-04 15:58 ` [PATCH 15/29] staging: bcm2835-audio: Drop debug messages in bcm2835-pcm.c Takashi Iwai
2018-09-04 15:58 ` [PATCH 16/29] staging: bcm2835-audio: Drop superfluous mutex lock during prepare Takashi Iwai
2018-09-08 13:40 ` Stefan Wahren
2018-09-08 16:12 ` Takashi Iwai
2018-09-04 15:58 ` [PATCH 17/29] staging: bcm2835-audio: Add 10ms period constraint Takashi Iwai
2018-09-19 9:42 ` Stefan Wahren [this message]
2018-09-19 9:52 ` Takashi Iwai
2018-09-19 12:41 ` Stefan Wahren
2018-09-19 12:47 ` Mike Brady
2018-09-19 18:39 ` Takashi Iwai
2018-10-09 13:18 ` [PATCH 17/29] staging: bcm2835-audio: Add 10ms period constraint [Resend in plain text...] Mike Brady
2018-10-09 13:44 ` Takashi Iwai
2018-10-09 15:28 ` Mike Brady
2018-10-09 15:32 ` Takashi Iwai
2018-10-11 12:53 ` Mike Brady
2018-10-11 14:07 ` Stefan Wahren
2018-10-13 15:00 ` Mike Brady
2018-10-13 15:45 ` Takashi Iwai
2018-09-04 15:58 ` [PATCH 18/29] staging: bcm2835-audio: Make single vchi handle Takashi Iwai
2018-09-04 15:58 ` [PATCH 19/29] staging: bcm2835-audio: Code refactoring of vchiq accessor codes Takashi Iwai
2018-09-04 15:58 ` [PATCH 20/29] staging: bcm2835-audio: Operate non-atomic PCM ops Takashi Iwai
2018-09-04 15:58 ` [PATCH 21/29] staging: bcm2835-audio: Use card->private_data Takashi Iwai
2018-09-04 15:58 ` [PATCH 22/29] staging: bcm2835-audio: Use standard error print helpers Takashi Iwai
2018-09-04 15:58 ` [PATCH 23/29] staging: bcm2835-audio: Remove unnecessary header file includes Takashi Iwai
2018-09-04 15:58 ` [PATCH 24/29] staging: bcm2835-audio: Move module parameter description Takashi Iwai
2018-09-04 15:58 ` [PATCH 25/29] staging: bcm2835-audio: Use coherent device buffers Takashi Iwai
2018-09-04 15:58 ` [PATCH 26/29] staging: bcm2835-audio: Set SNDRV_PCM_INFO_SYNC_APPLPTR Takashi Iwai
2018-09-04 15:58 ` [PATCH 27/29] staging: bcm2835-audio: Simplify PCM creation helpers Takashi Iwai
2018-09-04 15:58 ` [PATCH 28/29] staging: bcm2835-audio: Simplify kctl " Takashi Iwai
2018-09-04 15:58 ` [PATCH 29/29] staging: bcm2835-audio: Simplify card object management Takashi Iwai
2018-09-08 13:18 ` [PATCH 00/29] staging: bcm2835-audio: Cleanups and fixes Stefan Wahren
2018-09-08 16:21 ` Takashi Iwai
2018-09-08 17:00 ` Stefan Wahren
2018-09-08 17:16 ` Takashi Iwai
2018-09-10 9:12 ` Greg Kroah-Hartman
2018-09-10 9:16 ` Takashi Iwai
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