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

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Message-ID: <0bba90c1-01be-a76e-df12-2328b84f7298@linaro.org>
Date:   Fri, 21 Apr 2023 01:52:33 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        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>, 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 20/04/2023 22:56, Marijn Suijten wrote:
> On 2023-04-20 22:51:22, Dmitry Baryshkov wrote:
>> On 20/04/2023 22:47, Abhinav Kumar wrote:
>>>
>>>
>>> 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.
>>
>> Agree, this was the second item on my preference list. Could you please
>> send this oneliner?
> 
> Nit (to make sure we're on the same thought here): I think it's a
> 3-liner: remove it from DSPP_MSM8998_MASK as well as msm8998_dspp_sblk.
> 
>>> OR lets stay at (2) till
>>> someone does (1).
> 
> I'm personally okay leaving it in place too, with an eye on implementing
> this, IGC, and other blocks at some point if there's a use for it via
> standard DRM properties.

I took a quick glance. I think it is possible, but not straightforward. 
But I must admit here, I don't have a full picture regarding different 
color encodings, ranges and the rest of gamma/degamma API and usage.

> 
>>> When someone implements GC, we can re-use this patch and that time keep
>>> konrad's author rights or co-developed by.
> 
> Good to at least know all these SoCs have the same offset and revision.
> 
> - Marijn

-- 
With best wishes
Dmitry