Re: [PATCH] gpu: host1x: Skip reset assert on Tegra186

["Thierry Reding" <thierry.reding@gmail.com>]

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On Mon Feb 19, 2024 at 3:18 AM CET, Mikko Perttunen wrote:
> On 2/16/24 19:02, Thierry Reding wrote:
> > On Wed Feb 14, 2024 at 12:40 PM CET, Mikko Perttunen wrote:
> >> From: Mikko Perttunen <mperttunen@nvidia.com>
> >>
> >> On Tegra186, other software components may rely on the kernel to
> >> keep Host1x operational even during suspend. As such, as a quirk,
> >> skip asserting Host1x's reset on Tegra186.
> > 
> > This all sounds a bit vague. What other software components rely on the
> > kernel to keep host1x operational during suspend? And why do they do so?
> > Why is this not a problem elsewhere?
>
> My assumption is that it's due to a secure world application accessing 
> NVDEC or display engines during suspend or resume. This happening 
> without kernel knowledge is a bad thing, but it's hard to change at this 
> point.
>
> The reset line (CAR vs BPMP vs non-accessible reset line), and the 
> secure application code programming this stuff is slightly different in 
> every chip generation, which is where I think the differences happen.

*sigh*

I guess it is what it is. Please add a bit more background information
to the commit message and also a comment for the skip_reset field so
that people (including myself) will remember down the road why this
exists.

Thierry

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