On Thu, 18 May 2023 11:00:54 +0200, Cezary Rojewski wrote: > > On 2023-05-17 4:52 PM, Takashi Iwai wrote: > > On Wed, 17 May 2023 15:15:13 +0200, > > Cezary Rojewski wrote: > > ... > > >> After reading this conversation few times I came to conclusion that > >> codec device should be kept up as long as its runtime_status=0 > >> (RPM_ACTIVE), regardless if usage_count is 0 or not. Basically, in > >> autosuspend case usage_count and runtime_status for the device are > >> both 0 so, if we are not ignoring the former by calling > >> pm_runtime_get_if_in_use() then we end up caching the writes during > >> the autosuspend period - period when the device is no longer used but > >> there is still some time left before it's suspended. > >> > >> > >> --- a/sound/hda/hdac_device.c > >> +++ b/sound/hda/hdac_device.c > >> @@ -611,7 +611,7 @@ EXPORT_SYMBOL_GPL(snd_hdac_power_up_pm); > >> int snd_hdac_keep_power_up(struct hdac_device *codec) > >> { > >> if (!atomic_inc_not_zero(&codec->in_pm)) { > >> - int ret = pm_runtime_get_if_in_use(&codec->dev); > >> + int ret = pm_runtime_get_if_active(&codec->dev, true); > >> if (!ret) > >> return -1; > >> if (ret < 0) > >> > >> > >> Results for the above look good. > > > > OK, this seems to be a workaround. > > > > I took a deeper look at the issue now, and noticed that it's a messy > > problem. > > > While we want to address this issue first - I've even messaged you > about this for the very first time early 2021 :D but it's not marked > as high prio so it remained unaddressed till now - me and Amadeo spent > some time analyzing most of the pm-related code for sound/hda and we > believe most of it could be replaced by native pm_runtime_xxx code and > fields such as ->in_pm could be dropped. It's a bit tricky. The in_pm refcount check is mandatory because the very same code path is called recursively for enabling itself. > However, this won't take a > day or two and it's best if first we get to know the background > what/why/when some of those specific functions/members exist in the > hda code. Yeah, I'd love to clean up / fix the stuff, but this is in some sensitive area, so let's get it carefully. > > The check with pm_runtime_get_if_in_use() itself isn't wrong, but it > > needs the exceptional handling. > > > > In addition to that, however, we need to work around the case where > > the register gets updated twice with -EAGAIN handling; at the first > > update, the regcache gets updated while the actual write gives an > > error. Then at the second update, it checks only the cache and > > believes as if it's been already written, and the write is skipped. > > This was what Amadeusz experienced with my previous patch. > > So, we need to paper over those two. > > > > OTOH, if we replace the primary check with > > pm_runtime_get_if_active(true), this makes the things *mostly* > > working, too. This increases the usage count forcibly when the device > > is active, and we'll continue to write the register. > > The caveat is that the auto-suspend timer is still ticking in this > > case. But, this won't be a big problem, as the timer callback does > > check the state and cancel itself if the device is actually in use. > > > > So, I guess we should go for pm_runtime_get_if_in_use(). > > But please give it more tests. > > I believe you meant pm_runtime_get_if_active(true) in the last one. If > yes, then indeed I'm delaying the patch upload until more tests are > run. Ah correct, sorry for the typo, I mean *_if_active(). > Once again, thank you for the input. Ramping up and addressing this > problem wouldn't happen so quickly without your guidance. I'm going to submit your change as a proper fix patch soon later. Then let's dig down and tidy the rest things up. thanks, Takashi