On Mon, Jan 18, 2021 at 9:21 PM Takashi Iwai tiwai@suse.de wrote:

On Mon, 18 Jan 2021 14:09:36 +0100, Kai-Heng Feng wrote:

...

HDA controller can't be runtime-suspended after commit 215a22ed31a1 ("ALSA: hda: Refactor codjc PM to use direct-complete optimization"), which enables direct-complete for HDA codec.

The HDA codec driver didn't expect direct-complete will be disabled after it returns a positive value from prepare() callback. However, there are some places that PM core can disable direct-complete. For instance, system hibernation or when codec has subordinates like LEDs.

Hmm. This sounds rather like the approach using the direct-complete isn't well suited for the purpose? The increasing number of regression reports worries me.

Direct-complete works fine on HDA controller but so far not so on HDA codec. I think the main reason is that the codec doesn't have the middle layer to handle the detail, while HDA controller has PCI bus to deal with them.

...

So if a device is prepared for direct-complete but PM core still calls codec's suspend or freeze callback, resume the device to keep PM operations balanced.

I find the ping-pong of the resume/suspend there a bit odd. It's no refcount management but it invokes the real resume there, which is involved with lots of operations.

Yes. I'll find a better approach to address this.

Can we rather skip the hda_codec_suspend() call instead (while changing dev->power.power_state)?

Maybe we can revert the most of the commit, and just leave hda_codec_pm_complete(), which is the most relevant part of the patch. Let me test a bit and send a new patch. Let me know if you don't like this approach.

A question a bit unrelated to the discussion - how does snd_hdac_power_up_pm() work for concurrent resume? It can work for recursive call, but what if there are concurrent resume request, but pm_runtime_get_sync() is still running? The second call may access the codec which hasn't completed resume.

Kai-Heng

thanks,

Takashi

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Reported-by: Kenneth R. Crudup kenny@panix.com Fixes: 215a22ed31a1 ("ALSA: hda: Refactor codec PM to use direct-complete optimization") Signed-off-by: Kai-Heng Feng kai.heng.feng@canonical.com

---

sound/pci/hda/hda_codec.c | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c index 687216e74526..0afbced979df 100644 --- a/sound/pci/hda/hda_codec.c +++ b/sound/pci/hda/hda_codec.c @@ -2997,6 +2997,9 @@ static void hda_codec_pm_complete(struct device *dev)

static int hda_codec_pm_suspend(struct device *dev) {

• if (pm_runtime_status_suspended(dev))
  

•         pm_runtime_resume(dev);
  

• dev->power.power_state = PMSG_SUSPEND;
  return hda_codec_suspend(dev);
  

} @@ -3009,6 +3012,9 @@ static int hda_codec_pm_resume(struct device *dev)

static int hda_codec_pm_freeze(struct device *dev) {

• if (pm_runtime_status_suspended(dev))
  

•         pm_runtime_resume(dev);
  

• dev->power.power_state = PMSG_FREEZE;
  return hda_codec_suspend(dev);
  

}

2.29.2