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

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Message-ID: <1f7bb81a-d38c-725a-9ee1-89efe2950b1d@linaro.org>
Date:   Sat, 22 Apr 2023 01:35:21 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     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 22/04/2023 01:34, Abhinav Kumar wrote:
> 
> 
> On 4/20/2023 3:52 PM, Dmitry Baryshkov wrote:
>> 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.
>>
> 
> I think its easier to remove this now and then add it when we add the 
> support. As discussed, will post this shortly.
> 
> Otherwise, whenever any new chipset gets added, we will run into the 
> same question of whether to add GC or not.

Yes, I absolutely agree here.

> 
>>>
>>>>> 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