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

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Message-ID: <b77a3161-9a18-4523-8528-31c2f2f4f476@linaro.org>
Date: Tue, 9 Apr 2024 20:07:56 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Rob Clark <robdclark@...il.com>
Cc: 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 4/9/24 20:04, Dmitry Baryshkov wrote:
> On Tue, Apr 09, 2024 at 10:12:00AM -0700, Rob Clark wrote:
>> 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
> 
> Well, the issue is about an uknown speed bin. So in theory we know
> nothing about the set of speeds itsupports. My point is that we should
> simplfy fail in such case.

Or we could allow e.g. the lowest frequency (or 2) which if often shared
across the board to work, giving a compromise between OOBE and sanity

Konrad