linux-kernel - Re: [PATCH 3/6] drm/msm/adreno: Allow specifying default speedbin value

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Date: Tue, 9 Apr 2024 10:12:00 -0700
From: Rob Clark <robdclark@...il.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Konrad Dybcio <konrad.dybcio@...aro.org>, Bjorn Andersson <andersson@...nel.org>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	Neil Armstrong <neil.armstrong@...aro.org>
Subject: Re: [PATCH 3/6] drm/msm/adreno: Allow specifying default speedbin value

On Tue, Apr 9, 2024 at 8:23 AM Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> On Tue, Apr 09, 2024 at 05:12:46PM +0200, Konrad Dybcio wrote:
> >
> >
> > On 4/6/24 04:56, Dmitry Baryshkov wrote:
> > > On Fri, Apr 05, 2024 at 10:41:31AM +0200, Konrad Dybcio wrote:
> > > > From: Neil Armstrong <neil.armstrong@...aro.org>
> > > >
> > > > Usually, speedbin 0 is the "super SKU", a.k.a the one which can clock
> > > > the highest. Falling back to it when things go wrong is largely
> > > > suboptimal, as more often than not, the top frequencies are not
> > > > supposed to work on other bins.
> > >
> > > Isn't it better to just return an error here instead of trying to guess
> > > which speedbin to use?
> >
> > Not sure. I'd rather better compatibility for e.g. booting up a new
> > laptop with just dt.
>
> New speedbin can have lower max speed, so by attempting to run it at
> higher freq you might be breaking it.

Usually there are some OPPs in common to all speedbins, so picking a
freq from that set would seem like the safe thing to do

BR,
-R

>
> >
> > >
> > > If that's not the case, I think the commit should be expanded with
> > > actually setting default_speedbin for the existing GPUs.
> >
> > I think that should be addressed, although separately.
>
> I'd prefer to have it as a part of this patch, but I'd not NAK it just
> for this reason.
>
> --
> With best wishes
> Dmitry