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

[Sameer Pujar]

On 12/7/2021 7:37 PM, Dmitry Osipenko wrote:
> 07.12.2021 15:40, Sameer Pujar пишет:
> > 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?
> You have a shared power domain. Since power domain can be turned off
> only when nobody keeps domain turned on, you now making reset of HDA
> controller dependent on the state of display driver.

I don't think that the state of display driver would affect. The HDA 
driver itself can issue unpowergate calls which in turn ensures h/w 
reset. If display driver is already runtime active, HDA driver runtime 
resume after this would be still fine since h/w reset is already applied 
during display runtime resume. Note that both HDA and display resets are 
connected to this power-domain and BPMP applies these resets during 
unpowergate.

> Do you want to have
> inconsistent h/w reset behaviour depending on the runtime state of
> display driver?

Of course no.