linux-kernel - Re: [PATCH v2] drm/msm/dp: Enable support for eDP v1.4+ link rates table

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Message-ID: <chu5gqcvhqpeve7coitjo5iqf5n5cqipfyxpu2w5dm5tcjp66j@n3fg2qrgkara>
Date: Thu, 18 Dec 2025 03:13:07 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Dale Whinham <daleyo@...il.com>
Cc: Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jesszhan0024@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Jérôme de Bretagne <jerome.debretagne@...il.com>,
        Steev Klimaszewski <threeway@...il.com>
Subject: Re: [PATCH v2] drm/msm/dp: Enable support for eDP v1.4+ link rates
 table

On Thu, Dec 18, 2025 at 12:19:32AM +0000, Dale Whinham wrote:
> The MSM DRM driver currently does not support panels which report their
> supported link rates via the SUPPORTED_LINK_RATES table.
> 
> For panels which do not offer the optional eDP v1.3 fallback via
> MAX_LINK_RATE, this will cause a panel probe failure (e.g. Samsung
> ATNA30DW01-1 as found in Microsoft Surface Pro 11).
> 
> Detect eDP v1.4 panels and parse the SUPPORTED_LINK_RATES table when
> present.
> 
> Additionally, set the rate using LINK_RATE_SET instead of LINK_BW_SET,
> but only if LINK_BW_SET hasn't already been written to.
> 
> Signed-off-by: Dale Whinham <daleyo@...il.com>
> Tested-by: Jérôme de Bretagne <jerome.debretagne@...il.com>
> Tested-by: Steev Klimaszewski <threeway@...il.com>
> ---
> Changes in v2:
> - Re-ordered writing of LANE_COUNT_SET/LINK_BW_SET registers to match i915 [Dmitry]
> - Fix detection of eDP by reading EDP_CONFIGURATION_CAP and EDP_REV (in v1 we were mistakenly checking DPCD_REV) [Dmitry]
> - Link to v1: https://lore.kernel.org/r/20251214-drm-msm-edp14-v1-1-45de8c168cec@gmail.com
> ---
>  drivers/gpu/drm/msm/dp/dp_ctrl.c  | 56 ++++++++++++++---------
>  drivers/gpu/drm/msm/dp/dp_link.h  |  3 ++
>  drivers/gpu/drm/msm/dp/dp_panel.c | 93 ++++++++++++++++++++++++++++++++++-----
>  3 files changed, 120 insertions(+), 32 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>


-- 
With best wishes
Dmitry