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

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Date:   Sat,  1 Oct 2022 21:08:02 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     phone-devel@...r.kernel.org, Rob Clark <robdclark@...il.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Vinod Koul <vkoul@...nel.org>
Cc:     ~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>,
        Marijn Suijten <marijn.suijten@...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: [PATCH 0/5] drm: Fix math issues in MSM DSC implementation

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.

Altogether this series is responsible for solving _all_ Display Stream
Compression issues and artifacts on the Sony Tama (sdm845) Akatsuki
smartphone (2880x1440p).

Marijn Suijten (5):
  drm/msm/dsi: Remove useless math in DSC calculation
  drm/msm/dsi: Remove repeated calculation of slice_per_intf
  drm/msm/dsi: Account for DSC's bits_per_pixel having 4 fractional bits
  drm/msm/dpu1: Account for DSC's bits_per_pixel having 4 fractional
    bits
  drm/dsc: Prevent negative BPG offsets from shadowing adjacent
    bitfields

 drivers/gpu/drm/display/drm_dsc_helper.c   |  6 +--
 drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c | 11 +-----
 drivers/gpu/drm/msm/dsi/dsi_host.c         | 45 ++++++++++++++--------
 3 files changed, 33 insertions(+), 29 deletions(-)

--
2.37.3