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

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Message-ID: <50bf5a83-051e-8c12-6502-aabd8edd0a72@nvidia.com>
Date:   Tue, 14 Dec 2021 11:32:34 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, tiwai@...e.com,
        broonie@...nel.org, lgirdwood@...il.com, 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>, robh+dt@...nel.org
Subject: Re: [PATCH 1/3] ALSA: hda/tegra: Skip reset on BPMP devices



On 12/8/2021 5:35 PM, Dmitry Osipenko wrote:
> 08.12.2021 08:22, Sameer Pujar пишет:
>>
>> On 12/7/2021 11:32 PM, Dmitry Osipenko wrote
>>> If display is already active, then shared power domain is already
>>> ungated.
>> If display is already active, then shared power domain is already
>> ungated. HDA reset is already applied during this ungate. In other
>> words, HDA would be reset as well when display ungates power-domain.
> Now, if you'll reload the HDA driver module while display is active,
> you'll get a different reset behaviour. HDA hardware will be reset on
> pre-T186, on T186+ it won't be reset.

How the reset behavior is different? At this point when HDA driver is 
loaded the HW is already reset during display ungate. What matters, 
during HDA driver load, is whether the HW is in predictable state or not 
and the answer is yes. So I am not sure what problem you are referring 
to. Question is, if BPMP already ensures this, then why driver needs to 
take care of it.