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

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Message-ID: <7f7934e6-137c-4d8d-049b-0ed5e57cf00b@nvidia.com>
Date:   Mon, 28 Mar 2022 15:49:03 +0530
From:   Mohan Kumar D <mkumard@...dia.com>
To:     Takashi Iwai <tiwai@...e.de>
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 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.

>
> Takashi