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pcm: dshare: Added "hw_ptr_alignment" option in configuration for alignment of slave pointers

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This change adapt the fix commit 6b058fda9d
("pcm: dmix: Add option to allow alignment of slave pointers")
for dshare plugin

Issue is that snd_pcm_wait() goes back to waiting because the hw_ptr
is not period aligned. Therefore snd_pcm_wait() will block for a longer
time as required.

With these rcar driver changes the exact position of the dma is returned.
During snd_pcm_start they read hw_ptr as reference, and this hw_ptr
is now not period aligned, and is a little ahead over the period while it
is read. Therefore when the avail is calculated during snd_pcm_wait(),
it is missing the avail_min by a few frames.

An additional option hw_ptr_alignment is provided to dshare configuration,
to allow the user to configure the slave application and hw pointer
alignment at startup

Signed-off-by: Vanitha Channaiah <vanitha.channaiah@in.bosch.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Vanitha Channaiah 2019-05-15 11:56:33 +05:30 • committed by Takashi Iwai
parent 63ba5243ab
commit 7265e603bf
1 changed files with 35 additions and 5 deletions
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40
src/pcm/pcm_dshare.c
View file

@ -333,16 +333,16 @@ static int snd_pcm_dshare_reset(snd_pcm_t *pcm)
snd_pcm_direct_t *dshare = pcm->private_data;
dshare->hw_ptr %= pcm->period_size;
dshare->appl_ptr = dshare->last_appl_ptr = dshare->hw_ptr;
dshare->slave_appl_ptr = dshare->slave_hw_ptr = *dshare->spcm->hw.ptr;
snd_pcm_direct_reset_slave_ptr(pcm, dshare);
return 0;
}
static int snd_pcm_dshare_start_timer(snd_pcm_direct_t *dshare)
static int snd_pcm_dshare_start_timer(snd_pcm_t *pcm, snd_pcm_direct_t *dshare)
{
int err;
snd_pcm_hwsync(dshare->spcm);
dshare->slave_appl_ptr = dshare->slave_hw_ptr = *dshare->spcm->hw.ptr;
snd_pcm_direct_reset_slave_ptr(pcm, dshare);
err = snd_timer_start(dshare->timer);
if (err < 0)
return err;
@ -364,7 +364,8 @@ static int snd_pcm_dshare_start(snd_pcm_t *pcm)
else if (avail < 0)
return 0;
else {
if ((err = snd_pcm_dshare_start_timer(dshare)) < 0)
err = snd_pcm_dshare_start_timer(pcm, dshare);
if (err < 0)
return err;
snd_pcm_dshare_sync_area(pcm);
}
@ -547,7 +548,8 @@ static snd_pcm_sframes_t snd_pcm_dshare_mmap_commit(snd_pcm_t *pcm,
return 0;
snd_pcm_mmap_appl_forward(pcm, size);
if (dshare->state == STATE_RUN_PENDING) {
if ((err = snd_pcm_dshare_start_timer(dshare)) < 0)
err = snd_pcm_dshare_start_timer(pcm, dshare);
if (err < 0)
return err;
} else if (dshare->state == SND_PCM_STATE_RUNNING ||
dshare->state == SND_PCM_STATE_DRAINING) {
@ -755,6 +757,7 @@ int snd_pcm_dshare_open(snd_pcm_t **pcmp, const char *name,
dshare->slowptr = opts->slowptr;
dshare->max_periods = opts->max_periods;
dshare->var_periodsize = opts->var_periodsize;
dshare->hw_ptr_alignment = opts->hw_ptr_alignment;
dshare->sync_ptr = snd_pcm_dshare_sync_ptr;
retry:
@ -912,6 +915,12 @@ pcm.name {
ipc_key INT # unique IPC key
ipc_key_add_uid BOOL # add current uid to unique IPC key
ipc_perm INT # IPC permissions (octal, default 0600)
hw_ptr_alignment STR # Slave application and hw pointer alignment type
# STR can be one of the below strings :
# no
# roundup
# rounddown
# auto (default)
slave STR
# or
slave { # Slave definition
@ -936,6 +945,27 @@ pcm.name {
}
\endcode
<code>hw_ptr_alignment</code> specifies slave application and hw
pointer alignment type. By default hw_ptr_alignment is auto. Below are
the possible configurations:
- no: minimal latency with minimal frames dropped at startup. But
wakeup of application (return from snd_pcm_wait() or poll()) can
take up to 2 * period.
- roundup: It is guaranteed that all frames will be played at
startup. But the latency will increase upto period-1 frames.
- rounddown: It is guaranteed that a wakeup will happen for each
period and frames can be written from application. But on startup
upto period-1 frames will be dropped.
- auto: Selects the best approach depending on the used period and
buffer size.
If the application buffer size is < 2 * application period,
"roundup" will be selected to avoid under runs. If the slave_period
is < 10ms we could expect that there are low latency
requirements. Therefore "rounddown" will be chosen to avoid long
wakeup times. Such wakeup delay could otherwise end up with Xruns in
case of a dependency to another sound device (e.g. forwarding of
microphone to speaker). Else "no" will be chosen.
\subsection pcm_plugins_dshare_funcref Function reference
<UL>