linux-kernel - Re: [PATCH 1/3] ALSA: hda/tegra: Skip reset on BPMP devices

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Date:   Tue, 7 Dec 2021 18:10:09 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, tiwai@...e.com,
        broonie@...nel.org, lgirdwood@...il.com, robh+dt@...nel.org,
        thierry.reding@...il.com, perex@...ex.cz
Cc:     jonathanh@...dia.com, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Mohan Kumar <mkumard@...dia.com>
Subject: Re: [PATCH 1/3] ALSA: hda/tegra: Skip reset on BPMP devices



On 12/7/2021 5:35 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 07.12.2021 15:00, Sameer Pujar пишет:
>>
>> On 12/7/2021 3:52 PM, Dmitry Osipenko wrote:
>>> 07.12.2021 09:32, Sameer Pujar пишет:
>>>> HDA regression is recently reported on Tegra194 based platforms.
>>>> This happens because "hda2codec_2x" reset does not really exist
>>>> in Tegra194 and it causes probe failure. All the HDA based audio
>>>> tests fail at the moment. This underlying issue is exposed by
>>>> commit c045ceb5a145 ("reset: tegra-bpmp: Handle errors in BPMP
>>>> response") which now checks return code of BPMP command response.
>>>>
>>>> The failure can be fixed by avoiding above reset in the driver,
>>>> but the explicit reset is not necessary for Tegra devices which
>>>> depend on BPMP. On such devices, BPMP ensures reset application
>>>> during unpowergate calls. Hence skip reset on these devices
>>>> which is applicable for Tegra186 and later.
>>> The power domain is shared with the display, AFAICS. The point of reset
>>> is to bring h/w into predictable state. It doesn't make sense to me to
>>> skip the reset.
>> Yes the power-domain is shared with display. As mentioned above,
>> explicit reset in driver is not really necessary since BPMP is already
>> doing it during unpowergate stage. So the h/w is already ensured to be
>> in a good state.
> If you'll reload the driver module, then h/w won't be reset.

How the reload case would be different? Can you please specify more 
details if you are referring to a particular scenario?