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

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Date:   Mon, 28 Mar 2022 22:33:01 +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 9:45 PM, Takashi Iwai wrote:
> External email: Use caution opening links or attachments
>
>
> 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.
Sure, will take care same in next patch update.
>
> Takashi