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

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Date:   Mon, 28 Mar 2022 19:21:17 +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 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,
>
> Takashi