On Fri, 2019-04-05 at 14:30 +0200, 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?
Yes. That's correct.
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.
You'd need a flag indicating the BE hw_params resetup, and at the beginning of prepare function, the flag is checked and the (internal) hw_params is done accordingly.
This makes sense. Thank you for your help. We will change the flow accordingly.
Thanks, Ranjani
Takashi