From: Vanitha Channaiah vanitha.channaiah@in.bosch.com
This change adapt the fix commit 6b058fda9dce ("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 --- src/pcm/pcm_dshare.c | 40 +++++++++++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 5 deletions(-)
diff --git a/src/pcm/pcm_dshare.c b/src/pcm/pcm_dshare.c index f135b5d..cf8a863 100644 --- a/src/pcm/pcm_dshare.c +++ b/src/pcm/pcm_dshare.c @@ -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
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