[alsa-devel] [PATCH] [sound] hdac-codec runtime suspended at PM:Suspend.

[Lukas Wunner]

On Mon, Mar 26, 2018 at 09:30:36AM +0200, Takashi Iwai wrote:
> On Mon, 26 Mar 2018 09:03:55 +0200, Subhransu S. Prusty  wrote:
> > On Thu, Mar 15, 2018 at 09:02:30PM +0530, Anshuman Gupta wrote:
> > > On Thu, Mar 15, 2018 at 04:12:44PM +0530, Subhransu S. Prusty wrote:
> > > > This driver needs a late resume as it receives a jack notification
> > > > from the i915 driver and the skl controller driver resume may not
> > > > have happened and in turn hda controller may not ready. This ensures
> > > > a synchronization for jack event during resume from S3.
> > > 
> > > Let me give you insight of the issue, this driver blocks the direct
> > > complete of hda controller PCI 00:1f.3, sometimes it takes 280ms to
> > > resume hda controller from S3 and s2idle. So it does not make sense
> > > to suspend/resume hda controller when it is already in runtime
> > > suspend.
> 
> If it's about the power well issue, it had been fixed in multiple
> ways.  In i915 side, every relevant component callback is wrapped with
> power domain get/put.  And, at least HD-audio legacy side, such a
> spurious notification is filtered out in the eld notifier:
> 
> static void intel_pin_eld_notify(void *audio_ptr, int port, int pipe)
> {
> 	....
> 	/* skip notification during system suspend (but not in runtime PM);
> 	 * the state will be updated at resume
> 	 */
> 	if (snd_power_get_state(codec->card) != SNDRV_CTL_POWER_D0)
> 		return;
> 	/* ditto during suspend/resume process itself */
> 	if (atomic_read(&(codec)->core.in_pm))
> 		return;
> 
> 	snd_hdac_i915_set_bclk(&codec->bus->core);
> 	check_presence_and_report(codec, pin_nid, dev_id);
> }
> 
> Last but not least, the jack state is explicitly updated via reading
> the ELD at resume callback.
> 
> In that way, we can live with the standard suspend/resume procedure.

FWIW, the i915 folks have put on their todo list to migrate the
i915/hda_intel interaction to device links:

https://git.kernel.org/next/linux-next/c/7b3b61b62a58

Something similar has already been done for HDA controllers
integrated into AMD / Nvidia GPUs with:

https://git.kernel.org/next/linux-next/c/07f4f97d7b4b

With device links, direct_complete will be used naturally,
so time is probably best spent working towards this approach.

Thanks,

Lukas