On 4/5/19 7:30 AM, Takashi Iwai wrote:
On Thu, 04 Apr 2019 21:13:43 +0200,
Ranjani Sridharan wrote:
+
+ /* set runtime config */
+ runtime->hw.info = SNDRV_PCM_INFO_MMAP |
+ SNDRV_PCM_INFO_MMAP_VALID |
+ SNDRV_PCM_INFO_INTERLEAVED |
+ SNDRV_PCM_INFO_PAUSE |
+ SNDRV_PCM_INFO_RESUME |
+ SNDRV_PCM_INFO_NO_PERIOD_WAKEUP;
Does SOF support the full resume? That is, the stream gets resumed
at
the exact position that was suspended. Most devices can't, hence
they
don't set *_INFO_RESUME flag and let user-space restarting.
Hi Takashi,
Thanks for your comment. The SOF driver definitely cannot guarantee to
resume from the exact same position due to the fact that triggers for
the host dma and link dma are not synchronized and also IPC scheduling
will affect this. So we should remove INOF_RESUME from hw.info.
I do one follow up question for you. When a stream resumes/restarts
after suspend, we have the need for restoring the hw_params in the SOF
driver prior to handling the START trigger. I noticed that the
legacy/skylake driver does not seem to do this though. Do you have any
insights on what we might be missing in the SOF driver?
So, SOF mandates the re-setup of the hw params in BE at resume?
Then the right place to do is in the prepare callback. Without
SNDRV_PCM_INFO_RESUME flag, the PCM core won't trigger RESUME, but
returns -ENOSYS. Then user-space will do prepare, and start with the
normal trigger.
Takashi, some of us at Intel are a bit nervous about returning an error
to force the application to jump to its error-handling code (typically
only done for xruns and not always rock-solid) and as a side effect get
a prepare ioctl. I checked that e.g. CRAS does support this mode but I
wonder how many application developers know about this. I personally didn't.
Moreover, it seems that the default behavior is rather to support
RESUME, even if the hardware can't precisely restart from the same
position, so we are concerned about exposing new errors when SOF is
selected instead of legacy drivers (Baytrail, Atom-SST and Skylake-SST).
In short, is this really your recommendation to remove this INFO_RESUME
flag? And if yes, should we demote all existing Intel drivers and remove
this flag as well?
Thanks for your feedback
-Pierre
_______________________________________________
Alsa-devel mailing list
Alsa-devel@xxxxxxxxxxxxxxxx
https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
