linux-kernel - Re: [PATCH v2] drm/msm/adreno: Assign revn to A635

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Date:   Sun, 2 Jul 2023 17:34:39 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Stephen Boyd <swboyd@...omium.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Rob Clark <robdclark@...omium.org>
Subject: Re: [PATCH v2] drm/msm/adreno: Assign revn to A635

On 02/07/2023 17:31, Rob Clark wrote:
> On Sat, Jul 1, 2023 at 5:24 PM Dmitry Baryshkov
> <dmitry.baryshkov@...aro.org> wrote:
>>
>> On Sat, 1 Jul 2023 at 18:50, Rob Clark <robdclark@...il.com> wrote:
>>>
>>> On Fri, Jun 30, 2023 at 4:12 PM Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
>>>>
>>>> Recently, a WARN_ON() was introduced to ensure that revn is filled before
>>>> adreno_is_aXYZ is called. This however doesn't work very well when revn is
>>>> 0 by design (such as for A635). Fill it in as a stopgap solution for
>>>> -fixes.
>>>>
>>>> Fixes: cc943f43ece7 ("drm/msm/adreno: warn if chip revn is verified before being set")
>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>>> ---
>>>> Changes in v2:
>>>> - add fixes
>>>> - Link to v1: https://lore.kernel.org/r/20230628-topic-a635-v1-1-5056e09c08fb@linaro.org
>>>> ---
>>>>   drivers/gpu/drm/msm/adreno/adreno_device.c | 1 +
>>>>   1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
>>>> index cb94cfd137a8..8ea7eae9fc52 100644
>>>> --- a/drivers/gpu/drm/msm/adreno/adreno_device.c
>>>> +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
>>>> @@ -345,6 +345,7 @@ static const struct adreno_info gpulist[] = {
>>>>                  .address_space_size = SZ_16G,
>>>>          }, {
>>>>                  .rev = ADRENO_REV(6, 3, 5, ANY_ID),
>>>> +               .revn = 635,
>>>>                  .fw = {
>>>>                          [ADRENO_FW_SQE] = "a660_sqe.fw",
>>>>                          [ADRENO_FW_GMU] = "a660_gmu.bin",
>>>>
>>>
>>> hmm, I realized a problem with this, it would change what
>>> MSM_PARAM_GPU_ID and more importantly MSM_PARAM_CHIP_ID return..  The
>>> former should be "harmless", although it isn't a good idea for uabi
>>> changes to be a side effect of a fix.  The latter is more problematic.
>>
>> I'd say MSM_PARAM_GPU_ID is broken for 635 anyway (won't it return 0
>> in this case)?
>> So the new value should be correct.
> 
> no, it is very much intentional that GPU_ID returns 0 for newer GPUs,
> userspace should be matching on CHIP_ID.  (Also, we should be moving
> away from trying to infer generation/etc from CHIP_ID.. userspace is
> farther ahead of the kernel on this.)

Thanks for the explanation. So in theory we can change this to always 
return 0? Or must we keep it to keep UABI / compatibility?

I'm trying to understand if we can drop revn at all.


> 
>> But more importantly, why are we exporting speedbin in
>> MSM_PARAM_CHIP_ID only if there is no revn? And why are we exporting
>> the speedbin at all as a part of CHIP_ID?
> 
> Basically just being paranoid about not changing uabi.  It probably
> would be ok to export the speedbin for all, but I'd have to double
> check mesa version history.

Thanks!

> 
> BR,
> -R
> 
>>>
>>> I think I'm leaning more towards reverting commit cc943f43ece7
>>> ("drm/msm/adreno: warn if chip revn is verified before being set") for
>>> -fixes.  I'm still thinking about options for a longer term fix.
>>>
>>> BR,
>>> -R
>>>
>>>
>>>> ---
>>>> base-commit: 5c875096d59010cee4e00da1f9c7bdb07a025dc2
>>>> change-id: 20230628-topic-a635-1b3c2c987417
>>>>
>>>> Best regards,
>>>> --
>>>> Konrad Dybcio <konrad.dybcio@...aro.org>
>>>>
>>
>>
>>
>> --
>> With best wishes
>> Dmitry

-- 
With best wishes
Dmitry