linux-kernel - Re: [PATCH v5 0/4] drm/dp: Rework LTTPR transparent mode handling and add support to msm driver

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Message-ID: <87o6yq5kkv.fsf@intel.com>
Date: Tue, 25 Feb 2025 13:29:20 +0200
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, Abel Vesa
 <abel.vesa@...aro.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David
 Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Karol Herbst
 <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>, Danilo Krummrich
 <dakr@...hat.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>, Joonas Lahtinen
 <joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin <tursulin@...ulin.net>,
 Rob Clark <robdclark@...il.com>, Abhinav Kumar
 <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, Marijn Suijten
 <marijn.suijten@...ainline.org>, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>, Johan Hovold <johan@...nel.org>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 nouveau@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
 intel-xe@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
 freedreno@...ts.freedesktop.org, Johan Hovold <johan+linaro@...nel.org>,
 Imre Deak <imre.deak@...el.com>
Subject: Re: [PATCH v5 0/4] drm/dp: Rework LTTPR transparent mode handling
 and add support to msm driver

On Fri, 21 Feb 2025, Dmitry Baryshkov <dmitry.baryshkov@...aro.org> wrote:
> On Mon, Feb 03, 2025 at 12:57:55PM +0200, Abel Vesa wrote:
>> Looking at both i915 and nouveau DP drivers, both are setting the first
>> LTTPR (if found) in transparent mode first and then in non-transparent
>> mode, just like the DP v2.0 specification mentions in section 3.6.6.1.
>> 
>> Being part of the standard, setting the LTTPR in a specific operation mode
>> can be easily moved in the generic framework. So do that by adding a new
>> helper.
>> 
>> Then, the msm DP driver is lacking any kind of support for LTTPR handling,
>> so add it by reading the LTTPR caps for figuring out the number of LTTPRs
>> found on plug detect and then do exactly what the i915 and nouveau drivers
>> do with respect to toggling through operating modes, just like the
>> up-mentioned section from DP spec describes.
>> 
>> At some point, link training per sub-segment will probably be needed, but
>> for now, toggling the operating modes seems to be enough at least for the
>> X Elite-based platforms that this patchset has been tested on.
>> 
>> Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
>
> [...]
>> 
>> ---
>> Abel Vesa (4):
>>       drm/dp: Add helper to set LTTPRs in transparent mode
>>       drm/nouveau/dp: Use the generic helper to control LTTPR transparent mode
>>       drm/i915/dp: Use the generic helper to control LTTPR transparent mode
>
> Lyude, Jani, what would be your preferred way of merging these patches?
> Would you ack merging of those through drm-misc or would you prefer for
> the first patch only to be landed to drm-misc, which you can then pull
> into nouveau and i915 trees.

Either way is fine with me, up to you. But please try to ensure these
get into drm-misc-next pull request by this cycle, so we can backmerge
and catch up sooner rather than later.

Acked-by: Jani Nikula <jani.nikula@...el.com>



>
>>       drm/msm/dp: Add support for LTTPR handling
>> 
>>  drivers/gpu/drm/display/drm_dp_helper.c            | 61 ++++++++++++++++++++++
>>  .../gpu/drm/i915/display/intel_dp_link_training.c  | 24 ++-------
>>  drivers/gpu/drm/msm/dp/dp_display.c                | 15 ++++++
>>  drivers/gpu/drm/nouveau/nouveau_dp.c               | 17 +-----
>>  include/drm/display/drm_dp_helper.h                |  2 +
>>  5 files changed, 85 insertions(+), 34 deletions(-)
>> ---
>> base-commit: 00f3246adeeacbda0bd0b303604e46eb59c32e6e
>> change-id: 20241031-drm-dp-msm-add-lttpr-transparent-mode-set-136cd5bfde07
>> 
>> Best regards,
>> -- 
>> Abel Vesa <abel.vesa@...aro.org>
>> 

-- 
Jani Nikula, Intel