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

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Date: Tue, 9 Apr 2024 18:23:04 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>, 
	Rob Clark <robdclark@...il.com>, 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 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.

> 
> > 
> > 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