drm/msm/dp: cleared DP_DOWNSPREAD_CTRL register before start link training

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DOWNSPREAD_CTRL (0x107) shall be cleared to 0 upon power-on reset or an
upstream device disconnect. This patch will enforce this rule by always
cleared DOWNSPREAD_CTRL register to 0 before start link training. At rare
case that DP MSA timing parameters may be mis-interpreted by the sink
which causes audio sampling rate be calculated wrongly and cause audio
did not work at sink if DOWNSPREAD_CTRL register is not cleared to 0.

Changes in v2:
1) fix spelling at commit text
2) merge ssc variable into encoding[0]

Changes in v3:
-- correct spelling of DOWNSPREAD_CTRL
-- replace err with len of ssize_t

Changes in v4:
-- split into 2 patches

Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Fixes: c943b4948b ("drm/msm/dp: add displayPort driver support")
Patchwork: https://patchwork.freedesktop.org/patch/502532/
Link: https://lore.kernel.org/r/1662999830-13916-2-git-send-email-quic_khsieh@quicinc.com
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

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This commit is contained in:

Kuogee Hsieh 2022-09-12 09:23:48 -07:00 • committed by Abhinav Kumar

parent 152d394842

commit 70445dee1b

1 changed files with 5 additions and 8 deletions

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drivers/gpu/drm/msm/dp/dp_ctrl.c

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