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

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Date:   Sat, 22 Apr 2023 14:08:05 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     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 00:35, Dmitry Baryshkov wrote:
> 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.
Sorry for the useless patches, though I guess they were a good
discussion starter..

Konrad
> 
>>
>>>>
>>>>>> 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
>>>
>