linux-kernel - Re: [PATCH] drm/msm: Only enable A6xx LLCC code on A6xx

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Date:   Fri, 08 Jan 2021 19:35:33 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Konrad Dybcio <konrad.dybcio@...ainline.org>
Cc:     robdclark@...il.com, airlied@...ux.ie, airlied@...hat.com,
        akhilpo@...eaurora.org, angelogioacchino.delregno@...ainline.org,
        bjorn.andersson@...aro.org, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        jcrouse@...eaurora.org, jonathan@...ek.ca,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        marijn.suijten@...ainline.org, martin.botka@...ainline.org,
        phone-devel@...r.kernel.org, sean@...rly.run, shawn.guo@...aro.org,
        smasetty@...eaurora.org, ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH] drm/msm: Only enable A6xx LLCC code on A6xx

On 2021-01-08 19:09, Konrad Dybcio wrote:
>> Konrad, can you please test this below change without your change?
> 
> This brings no difference, a BUG still happens. We're still calling
> to_a6xx_gpu on ANY device that's probed! Too bad it won't turn my A330
> into an A640..
> 
> Also, relying on disabling LLCC in the config is out of question as it
> makes the arm32 kernel not compile with DRM/MSM and it just removes
> the functionality on devices with a6xx.. (unless somebody removes the
> dependency on it, which in my opinion is even worse and will cause
> more problems for developers!).
> 

Disabling LLCC is not the suggestion, I was under the impression that
was the cause here for the smmu bug. Anyways, the check for llc slice
in case llcc is disabled is not correct as well. I will send a patch for
that as well.

> The bigger question is how and why did that piece of code ever make it
> to adreno_gpu.c and not a6xx_gpu.c?
> 

My mistake, I will move it.

> To solve it in a cleaner way I propose to move it to an a6xx-specific
> file, or if it's going to be used with next-gen GPUs, perhaps manage
> calling of this code via an adreno quirk/feature in adreno_device.c.
> Now that I think about it, A5xx GPMU en/disable could probably managed
> like that, instead of using tons of if-statements for each GPU model
> that has it..
> 
> While we're at it, do ALL (and I truly do mean ALL, including the
> low-end ones, this will be important later on) A6xx GPUs make use of
> that feature?
> 

I do not have a list of all A6XX GPUs with me currently, but from what
I know, A618, A630, A640, A650 has the support.

Thanks,
Sai

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