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

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Message-ID: <57pxyxwluu33z4lpij5gx7biwfo5pbhdalhhxflw7esi5n3vts@qhjb7ldnz3wb>
Date:   Thu, 20 Apr 2023 21:56:22 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.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 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.

> > 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