linux-kernel - Re: [PATCH] ALSA: hda: Avoid unsol event during RPM suspending

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Date:   Mon, 28 Mar 2022 18:15:53 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Mohan Kumar D <mkumard@...dia.com>
Cc:     tiwai@...e.com, kai.vehmanen@...ux.intel.com, perex@...ex.cz,
        ville.syrjala@...ux.intel.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, thierry.reding@...il.com,
        jonathanh@...dia.com
Subject: Re: [PATCH] ALSA: hda: Avoid unsol event during RPM suspending

On Mon, 28 Mar 2022 15:51:17 +0200,
Mohan Kumar D wrote:
> 
> 
> On 3/28/2022 4:27 PM, Takashi Iwai wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > On Mon, 28 Mar 2022 12:19:03 +0200,
> > Mohan Kumar D wrote:
> >>
> >> On 3/28/2022 3:12 PM, Takashi Iwai wrote:
> >>> External email: Use caution opening links or attachments
> >>>
> >>>
> >>> On Mon, 28 Mar 2022 11:14:11 +0200,
> >>> Mohan Kumar wrote:
> >>>> There is a corner case with unsol event handling during codec runtime
> >>>> suspending state. When the codec runtime suspend call initiated, the
> >>>> codec->in_pm atomic variable would be 0, currently the codec runtime
> >>>> suspend function calls snd_hdac_enter_pm() which will just increments
> >>>> the codec->in_pm atomic variable. Consider unsol event happened just
> >>>> after this step and before snd_hdac_leave_pm() in the codec runtime
> >>>> suspend function. The snd_hdac_power_up_pm() in the unsol event
> >>>> flow in hdmi_present_sense_via_verbs() function would just increment
> >>>> the codec->in_pm atomic variable without calling pm_runtime_get_sync
> >>>> function.
> >>>>
> >>>> As codec runtime suspend flow is already in progress and in parallel
> >>>> unsol event is also accessing the codec verbs, as soon as codec
> >>>> suspend flow completes and clocks are  switched off before completing
> >>>> the unsol event handling as both functions doesn't wait for each other.
> >>>> This will result in below errors
> >>>>
> >>>> [  589.428020] tegra-hda 3510000.hda: azx_get_response timeout, switching
> >>>> to polling mode: last cmd=0x505f2f57
> >>>> [  589.428344] tegra-hda 3510000.hda: spurious response 0x80000074:0x5,
> >>>> last cmd=0x505f2f57
> >>>> [  589.428547] tegra-hda 3510000.hda: spurious response 0x80000065:0x5,
> >>>> last cmd=0x505f2f57
> >>>>
> >>>> To avoid this, the unsol event flow should not perform any codec verb
> >>>> related operations during RPM_SUSPENDING state.
> >>>>
> >>>> Signed-off-by: Mohan Kumar <mkumard@...dia.com>
> >>> Thanks, that's a hairy problem...
> >>>
> >>> The logic sounds good, but can we check the PM state before calling
> >>> snd_hda_power_up_pm()?
> >> If am not wrong, PM apis exposed either provide RPM_ACTIVE or
> >> RPM_SUSPENDED status. Don't see anything which provides info on
> >> RPM_SUSPENDING. We might need to exactly know this state to fix this
> >> issue.
> > Well, maybe my question wasn't clear.  What I meant was that your
> > change below
> >
> >>        ret = snd_hda_power_up_pm(codec);
> >> -     if (ret < 0 && pm_runtime_suspended(hda_codec_dev(codec)))
> >> +     if ((ret < 0 && pm_runtime_suspended(dev)) ||
> >> +             (dev->power.runtime_status == RPM_SUSPENDING))
> >>                goto out;
> > can be rather like:
> >
> >> +     if (dev->power.runtime_status == RPM_SUSPENDING)
> >> +             return;
> >>        ret = snd_hda_power_up_pm(codec);
> >>        if (ret < 0 && pm_runtime_suspended(hda_codec_dev(codec)))
> > so that it skips unneeded power up/down calls.
> >
> > Basically the state is set at drivers/base/power/runtime.c
> > rpm_suspend() just before calling the device's runtime_suspend
> > callback.  So the state is supposed to be same before and after
> > snd_hda_power_up_pm() in that case.
> Thanks!, Make sense, will push the updated patch after testing with
> latest suggestion.

Thanks.  Also don't forget to cover a case the test bot complained:
the reference to power.runtime_status needs #ifdef CONFIG_PM.


Takashi