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From:   Rob Clark <robdclark@gmail.com>
Date:   Fri, 8 Jan 2021 08:46:52 -0800
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Subject: Re: [Freedreno] [PATCH] drm/msm: Only enable A6xx LLCC code on A6xx
To:     Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc:     Konrad Dybcio <konrad.dybcio@somainline.org>,
        Sean Paul <sean@poorly.run>,
        Jordan Crouse <jcrouse@codeaurora.org>,
        Jonathan <jonathan@marek.ca>, David Airlie <airlied@linux.ie>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Sharat Masetty <smasetty@codeaurora.org>,
        martin.botka@somainline.org,
        Akhil P Oommen <akhilpo@codeaurora.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Shawn Guo <shawn.guo@linaro.org>,
        marijn.suijten@somainline.org,
        ~postmarketos/upstreaming@lists.sr.ht,
        Daniel Vetter <daniel@ffwll.ch>,
        angelogioacchino.delregno@somainline.org,
        Dave Airlie <airlied@redhat.com>, phone-devel@vger.kernel.org,
        freedreno <freedreno@lists.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Fri, Jan 8, 2021 at 6:05 AM Sai Prakash Ranjan
<saiprakash.ranjan@codeaurora.org> wrote:
>
> 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.

Thanks, since we don't have kernel-CI coverage for gpu, and there
probably isn't one person who has all the different devices supported
(or enough hours in the day to test them all), it is probably
better/safer to keep things in the backend code that is specific to a
given generation.

> > 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.
>

From the PoV of bringing up new a6xx, we should probably consider that
some of them may not *yet* have LLCC enabled.  I have an 8cx laptop
and once I find time to get the display working, the next step would
be bringing up a680.. and I'd probably like to start without LLCC..

BR,
-R

> Thanks,
> Sai
>
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
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