Re: [PATCH v7 00/10] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus

From: Lyude Paul <lyude@redhat.com>
To: Douglas Anderson <dianders@chromium.org>,
	Andrzej Hajda <a.hajda@samsung.com>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	Sam Ravnborg <sam@ravnborg.org>
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>,
	Thierry Reding <treding@nvidia.com>,
	Stephen Boyd <swboyd@chromium.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	linux-arm-msm@vger.kernel.org,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Linus W <linus.walleij@linaro.org>,
	dri-devel@lists.freedesktop.org, robdclark@chromium.org,
	Steev Klimaszewski <steev@kali.org>,
	Andy Gross <agross@kernel.org>, Daniel Vetter <daniel@ffwll.ch>,
	David Airlie <airlied@linux.ie>,
	Maxime Ripard <mripard@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Robert Foss <robert.foss@linaro.org>,
	Sandeep Panda <spanda@codeaurora.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 00/10] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus
Date: Fri, 21 May 2021 19:07:51 -0400	[thread overview]
Message-ID: <2536404ca2ab0e7b785a104ec6b4efb48943a438.camel@redhat.com> (raw)
In-Reply-To: <20210517200907.1459182-1-dianders@chromium.org>

For patches 5, and 6:

Reviewed-by: Lyude Paul <lyude@redhat.com>

This week got really busy so I wasn't able to look at the rest of them, but next
week is going to be a lot less busy so I should be able to look at them then

On Mon, 2021-05-17 at 13:08 -0700, Douglas Anderson wrote:
> The primary goal of this series is to try to properly fix EDID reading
> for eDP panels using the ti-sn65dsi86 bridge.
> 
> Previously we had a patch that added EDID reading but it turned out
> not to work at bootup. This caused some extra churn at bootup as we
> tried (and failed) to read the EDID several times and also ended up
> forcing us to use the hardcoded mode at boot. With this patch series I
> believe EDID reading is reliable at boot now and we never use the
> hardcoded mode.
> 
> High level note: in this series the EDID reading is driven by the
> panel driver, not by the bridge chip driver. I believe this makes a
> reasonable amount of sense since the panel driver already _could_
> drive reading the EDID if provided with the DDC bus and in future
> planned work we'll want to give the panel driver the DDC bus (to make
> decisions based on EDID) and the AUX bus (to control the
> backlight). There are also planned patches from Laurent to make
> ti-sn65dsi86 able to drive full DP monitors. In that case the bridge
> chip will still be in charge of reading the EDID, but it's not hard to
> make this dynamic.
> 
> This series is the logical successor to the 3-part series containing
> the patch ("drm/bridge: ti-sn65dsi86: Properly get the EDID, but only
> if refclk") [1].
> 
> This patch was tested against drm-misc-next commit 60a6b73dd821
> ("drm/ingenic: Fix pixclock rate for 24-bit serial panels") on a
> sc7180-trogdor-lazor device.
> 
> At v7 now, this patch series grew a bit from v6 because it introduces
> the DP AUX bus.
> 
> Between v2 and v3, high-level view of changes:
> - stop doing the EDID caching in the core.
> 
> Between v3 and v4, high-level view of changes:
> - EDID reading is actually driven by the panel driver now. See above.
> - Lots of chicken-and-egg problems solved w/ sub-devices.
> 
> Between v4 and v5, high-level view of changes.
> - Some of the early patches landed, so dropped from series.
> - New pm_runtime_disable() fix (fixed a patch that already landed).
> - Added Bjorn's tags to most patches
> - Fixed problems when building as a module.
> - Reordered debugfs patch and fixed error handling there.
> - Dropped last patch. I'm not convinced it's safe w/out more work.
> 
> Between v5 and v6, high-level view of changes:
> - Added the patch ("drm/dp: Allow an early call to register DDC i2c
>   bus")
> - Many patches had been landed, so only a few "controversial" ones
>   left.
> 
> Between v6 and v7, high-level view of changes:
> - New AUX DP bus!
> 
> [1]
> https://lore.kernel.org/r/20210304155144.3.I60a7fb23ce4589006bc95c64ab8d15c74b876e68@changeid/
> 
> Changes in v7:
> - pm_runtime_dont_use_autosuspend() fix new for v7.
> - List hpd properties bindings patch new for v7.
> - ti-sn65dsi86: Add aux-bus child patch new for v7.
> - Patch introducing the DP AUX bus is new for v7.
> - Patch to allow panel-simple to be DP AUX EP new for v7.
> - Patch using the DP AUX for DDC new for v7.
> - Remove use of now-dropped drm_dp_aux_register_ddc() call.
> - Beefed up commit message in context of the DP AUX bus.
> - Set the proper sub-device "dev" pointer in the AUX structure.
> - Patch to support for DP AUX bus on ti-sn65dsi86 new for v7.
> - Adjusted commit message to talk about DP AUX bus.
> - Panel now under bridge chip instead of getting a link to ddc-i2c
> 
> Changes in v6:
> - Use new drm_dp_aux_register_ddc() calls.
> 
> Douglas Anderson (10):
>   drm/panel: panel-simple: Add missing pm_runtime_dont_use_autosuspend()
>     calls
>   dt-bindings: display: simple: List hpd properties in panel-simple
>   dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child
>   drm: Introduce the DP AUX bus
>   drm/panel: panel-simple: Allow panel-simple be a DP AUX endpoint
>     device
>   drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC
>   drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev
>   drm/bridge: ti-sn65dsi86: Add support for the DP AUX bus
>   drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC
>   arm64: dts: qcom: sc7180-trogdor: Move panel under the bridge chip
> 
>  .../bindings/display/bridge/ti,sn65dsi86.yaml |  22 +-
>  .../bindings/display/panel/panel-simple.yaml  |   2 +
>  arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi  |  30 +-
>  drivers/gpu/drm/Kconfig                       |   5 +
>  drivers/gpu/drm/Makefile                      |   2 +
>  drivers/gpu/drm/bridge/Kconfig                |   1 +
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c         | 111 ++++--
>  drivers/gpu/drm/drm_dp_aux_bus.c              | 322 ++++++++++++++++++
>  drivers/gpu/drm/panel/Kconfig                 |   1 +
>  drivers/gpu/drm/panel/panel-simple.c          |  66 +++-
>  include/drm/drm_dp_aux_bus.h                  |  57 ++++
>  11 files changed, 563 insertions(+), 56 deletions(-)
>  create mode 100644 drivers/gpu/drm/drm_dp_aux_bus.c
>  create mode 100644 include/drm/drm_dp_aux_bus.h
> 

-- 
Sincerely,
   Lyude Paul (she/her)
   Software Engineer at Red Hat

Note: I deal with a lot of emails and have a lot of bugs on my plate. If you've
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