linux-kernel - Re: [PATCH 0/2] DPU1 GC1.8 wiring-up

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Date:   Thu, 20 Apr 2023 12:47:50 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
CC:     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>
Subject: Re: [PATCH 0/2] DPU1 GC1.8 wiring-up



On 4/20/2023 11:01 AM, Dmitry Baryshkov wrote:
> On 20/04/2023 04:36, Konrad Dybcio wrote:
>>
>>
>> On 20.04.2023 03:28, Abhinav Kumar wrote:
>>>
>>>
>>> On 4/19/2023 6:26 PM, Konrad Dybcio wrote:
>>>>
>>>>
>>>> On 20.04.2023 03:25, Dmitry Baryshkov wrote:
>>>>> On 20/04/2023 04:14, Konrad Dybcio wrote:
>>>>>> Almost all SoCs from SDM845 to SM8550 inclusive feature a GC1.8
>>>>>> dspp sub-block in addition to PCCv4. The other block differ a bit
>>>>>> more, but none of them are supported upstream.
>>>>>>
>>>>>> This series adds configures the GCv1.8 on all the relevant SoCs.
>>>>>
>>>>> Does this mean that we will see gamma_lut support soon?
>>>> No promises, my plate is not even full, it's beyond overflowing! :P
>>>>
>>>> Konrad
>>>
>>> So I think I wrote about this before during the catalog rework/fixes 
>>> that the gc registers are not written to / programmed.
>>>
>>> If thats not done, is there any benefit to this series?
>> Completeness and preparation for the code itself, if nothing else?
> 
> The usual problem is that if something is not put to use, it quickly 
> rots or becomes misused for newer platforms. We have seen this with the 
> some of DPU features.
> 
> In case of GC (and the freshly defined DPU_DSPP_IGC, but not used) we 
> have three options:
> - drop the unused GC from msm8998_sblk.
> - keep things as is, single unused GC entry
> - fill all the sblk with the correct information in hope that it stays 
> correct
> 
> Each of these options has its own drawbacks. I have slight bias towards 
> the last option, to have the information in place (as long as it is 
> accurate).
> 

My vote is for (1) . Today, GC is unused and from the discussion here, 
there is no concrete plan to add it. If we keep extending an unused 
bitmask for all the chipsets including the ones which will get added in 
the future in the hope that someday the feature comes, it doesnt sound 
like a good idea.

I would rather do (1), if someone has time. OR lets stay at (2) till 
someone does (1).

When someone implements GC, we can re-use this patch and that time keep 
konrad's author rights or co-developed by.