linux-kernel - Re: [RFC PATCH 5/7] drm/msm/dpu: Document and enable TEAR interrupts on DSI interfaces

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Date:   Mon, 17 Apr 2023 21:41:07 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        phone-devel@...r.kernel.org,
        Neil Armstrong <neil.armstrong@...aro.org>,
        ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Stephen Boyd <swboyd@...omium.org>,
        Vinod Koul <vkoul@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Loic Poulain <loic.poulain@...aro.org>,
        Vinod Polimera <quic_vpolimer@...cinc.com>,
        Adam Skladowski <a39.skl@...il.com>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 5/7] drm/msm/dpu: Document and enable TEAR interrupts
 on DSI interfaces

On 2023-02-14 09:54:57, Abhinav Kumar wrote:
[..]
> >>>> Just wondering, how were the lengths calculated for the INTF blocks?
> >>>> The values in general seem a little off to me.
> > 
> > These (for MSM8998) have been taken from downstream specifically; my
> > series starts using INTF_STATUS at 0x26C which conveniently is the
> > register right after 0x268, matching the fact that INTF TE and these
> > registers weren't supported/available yet on MSM8998.
> > 
> >>>> For example, I'm looking downstream and it seems to me that the length
> >>>> for the INTF_0 on MSM8998 should be 0x280. Similarly for SC7280, I'm
> >>>> seeing that length for INTF + tearcheck should be 0x2c4.
> > 
> > There are many different downstream sources and tags with seemingly
> > conflicting/confusing information.  For v2 [2] I've picked the highest
> > register used by the driver which is INTF_TEAR_AUTOREFRESH_CONFIG at
> > 0x2B4 (but there might always be more registers that don't need to be
> > poked at by the driver, but contain magic debug information and the
> > like... those would be useful to capture in the dump going forward).
> > 
> > [2]: https://github.com/SoMainline/linux/commit/2bbc609dd28aa0bd0a2dede20163e521912d0072
> > 
> 
> Not entirely correct.TEAR_AUTOREFRESH_STATUS is at 0x2c0 for sm8350 and 
> sm8450 as well so 0x2b4 is a bit short. DPU code uses autorefresh status 
> today.Esp after your changes it will use the autorefresh status from 
> intf te which is at offset 0x2c0

Revisiting this, I don't see current DPU code nor downstream 5.4 / 5.10
SDE techpack on some of my checkouts use this register, only
INTF_TEAR_AUTOREFRESH_CONFIG at 0x2b4..0x2b7.  Am I missing something
critical here?

> >>> We have discussed INTF lengths in [1]. The current understanding of the
> >>> block lengths can be found at [2]. Please comment there if any of the
> >>> fixed lengths sounds incorrect to you.
> >>>
> >>> [1] https://patchwork.freedesktop.org/patch/522187/
> >>> [2] https://patchwork.freedesktop.org/patch/522227/
> >>>
> >>> [skipped the rest]
> >>>
> >>
> >> Please correct my understanding here, it was agreed to fix intf blocks
> >> to 0x2c4 here https://patchwork.freedesktop.org/patch/522227/ but I dont
> >> see this was merged?
> >>
> >> It was agreed to first land INTF_TE and then add the higher addresses
> > 
> > Seems like it, at least if I interpret [3] correctly.  My series adds a
> > new define that will hardcode _len to 0x2B8 for now, and Dmitry/Konrad
> > can later extend it to whatever is stated by the correct downstream
> > source.
> > 
> 
> Like mentioned above it should be 0x2c0 for intf block.
> 
> If you face any conflicting information in downstream code, you can 
> always check with me on IRC.

Ack, it looks like others landed these changes for me now via the
catalog rework, so I have just rebased and kept the lengths in.

- Marijn