linux-kernel - Re: [PATCH 0/5] drm: Fix math issues in MSM DSC implementation

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Message-ID: <20221004095114.tr2gk76epbycflfa@SoMainline.org>
Date:   Tue, 4 Oct 2022 11:51:14 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     phone-devel@...r.kernel.org, Rob Clark <robdclark@...il.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        Douglas Anderson <dianders@...omium.org>,
        Vladimir Lypak <vladimir.lypak@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org
Subject: Re: [PATCH 0/5] drm: Fix math issues in MSM DSC implementation

On 2022-10-04 10:12:58, Vinod Koul wrote:
> On 01-10-22, 21:08, Marijn Suijten wrote:
> > Various removals of complex yet unnecessary math, fixing all uses of
> > drm_dsc_config::bits_per_pixel to deal with the fact that this field
> > includes four fractional bits, and finally an approach for dealing with
> > dsi_host setting negative values in range_bpg_offset, resulting in
> > overflow inside drm_dsc_pps_payload_pack().
> > 
> > Note that updating the static bpg_offset array to limit the size of
> > these negative values to 6 bits changes what would be written to the DPU
> > hardware at register(s) DSC_RANGE_BPG_OFFSET, hence the choice has been
> > made to cover up for this while packing the value into a smaller field
> > instead.
> 
> Thanks for fixing these. I dont have my pixel3 availble but changes lgtm
> 
> Reviewed-by: Vinod Koul <vkoul@...nel.org>

Thanks; any comment on the self-review I sent in for patch 3 and 5?

> > Altogether this series is responsible for solving _all_ Display Stream
> > Compression issues and artifacts on the Sony Tama (sdm845) Akatsuki
> > smartphone (2880x1440p).
> 
> Does it need two dsi lanes?

This panel has the default of four dsi data lanes enabled:

https://github.com/sonyxperiadev/kernel/blob/f956fbd9a234033bd18234d456a2c32c126b38f3/arch/arm64/boot/dts/qcom/dsi-panel-somc-akatsuki.dtsi#L74-L77

Unless you are referring to dual-dsi (ctrl/phy); this panel doesn't have
a dual connection, but I do have devices on sm8350/sm8450 with a
"4k"@120Hz display that have this, in case you want it to be tested?

However, for the time being I'm focussing on a similar panel (4 data
lanes, single DSI ctrl/phy) on sm8250 which keeps showing corrupted /
garbled data and resulting in ping-pong timeouts.  I haven't yet
confirmed if this is due to the "integration" of the pingpong block with
the intf (since relevant registers and interrupts still seem to be
accessible), a mismatching resource topology, or a misconfiguration
elswhere.  Relevant panel dts if you're interested:

https://github.com/sonyxperiadev/kernel/blob/e70161ec43b147b0b02578d05ab64552fd2df2cd/arch/arm64/boot/dts/somc/dsi-panel-sofef03_m-fhd_plus.dtsi

- Marijn