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Date:   Mon, 28 Mar 2022 12:57:31 +0200
Message-ID: <s5ha6dal4ys.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Mohan Kumar D <mkumard@nvidia.com>
Cc:     tiwai@suse.com, kai.vehmanen@linux.intel.com, perex@perex.cz,
        ville.syrjala@linux.intel.com, alsa-devel@alsa-project.org,
        linux-kernel@vger.kernel.org, thierry.reding@gmail.com,
        jonathanh@nvidia.com
Subject: Re: [PATCH] ALSA: hda: Avoid unsol event during RPM suspending
In-Reply-To: <7f7934e6-137c-4d8d-049b-0ed5e57cf00b@nvidia.com>
References: <20220328091411.31488-1-mkumard@nvidia.com>
        <s5hczi6l8fz.wl-tiwai@suse.de>
        <7f7934e6-137c-4d8d-049b-0ed5e57cf00b@nvidia.com>
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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@nvidia.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,

Takashi