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From: Douglas Anderson <dianders@chromium.org>
To: Andrzej Hajda <a.hajda@samsung.com>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Jonas Karlman <jonas@kwiboo.se>, Sam Ravnborg <sam@ravnborg.org>
Cc: robdclark@chromium.org, devicetree@vger.kernel.org,
	David Airlie <airlied@linux.ie>,
	linux-arm-msm@vger.kernel.org,
	Douglas Anderson <dianders@chromium.org>,
	Steev Klimaszewski <steev@kali.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>,
	Rob Herring <robh+dt@kernel.org>,
	dri-devel@lists.freedesktop.org,
	Stephen Boyd <swboyd@chromium.org>,
	Thierry Reding <treding@nvidia.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus
Date: Mon, 24 May 2021 17:01:50 -0700	[thread overview]
Message-ID: <20210524165920.v8.2.Id3c048d22e72a9f90084a543b5b4e3f43bc9ab62@changeid> (raw)
In-Reply-To: <20210525000159.3384921-1-dianders@chromium.org>

We want to be able to list an eDP panel as a child of an eDP
controller node to represent the fact that the panel is connected to
the controller's DP AUX bus. Though the panel and the controller are
connected in several ways, the DP AUX bus is the primary control
interface between the two and thus makes the most sense to model in
device tree hierarchy.

Listing a panel in this way makes it possible for the panel driver to
easily get access to the DP AUX bus that it resides on, which can be
useful to help in auto-detecting the panel and for turning on various
bits.

NOTE: historically eDP panels were _not_ listed under their controller
but were listed at the top level of the device tree. This will still
be supported for backward compatibility (and while DP controller
drivers are adapted to support the new DT syntax) but should be
considered deprecated since there is no downside to listing the panel
under the controller.

For now, the DP AUX bus bindings will only support an eDP panel
underneath. It's possible it could be extended to allow having a DP
connector under it in the future.

The idea for this bus's design was hashed out over IRC [1].

[1] https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&date=2021-05-11

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
My DT yaml-fu is still weak. If I did something stupid, please help me
learn how to do this better!

NOTE: there is no "Example" in this bindings file. Yikes! This is
because I wanted to keep this patch separate from the one that enables
the first eDP controller. See the patch ("dt-bindings: drm/aux-bus:
Add an example") for the example.

ALSO: if anyone else would like to be listed as a "Maintainer" in this
file then please shout!

Changes in v8:
- Separate DP AUX bus binding is new for v8.

 .../bindings/display/dp-aux-bus.yaml          | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/dp-aux-bus.yaml

diff --git a/Documentation/devicetree/bindings/display/dp-aux-bus.yaml b/Documentation/devicetree/bindings/display/dp-aux-bus.yaml
new file mode 100644
index 000000000000..5e4afe9f98fb
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/dp-aux-bus.yaml
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/dp-aux-bus.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: DisplayPort AUX bus
+
+maintainers:
+  - Douglas Anderson <dianders@chromium.org>
+
+description:
+  DisplayPort controllers provide a control channel to the sinks that
+  are hooked up to them. This is the DP AUX bus. Over the DP AUX bus
+  we can query properties about a sink and also configure it. In
+  particular, DP sinks support DDC over DP AUX which allows tunneling
+  a standard I2C DDC connection over the AUX channel.
+
+  To model this relationship, DP sinks should be placed as children
+  of the DP controller under the "aux-bus" node.
+
+  At the moment, this binding only handles the eDP case. It is
+  possible it will be extended in the future to handle the DP case.
+  For DP, presumably a connector would be listed under the DP AUX
+  bus instead of a panel.
+
+properties:
+  $nodename:
+    const: "aux-bus"
+
+  panel:
+    $ref: panel/panel-common.yaml#
+
+additionalProperties: false
+
+required:
+  - panel
-- 
2.31.1.818.g46aad6cb9e-goog


  parent reply	other threads:[~2021-05-25  0:02 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-25  0:01 [PATCH v8 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing " Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple Douglas Anderson
2021-06-02 18:00   ` Rob Herring
2021-05-25  0:01 ` Douglas Anderson [this message]
2021-06-02 18:08   ` [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus Rob Herring
2021-05-25  0:01 ` [PATCH v8 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child Douglas Anderson
2021-05-28  0:29   ` Linus Walleij
2021-06-02 18:06     ` Rob Herring
2021-06-02 18:09       ` Rob Herring
2021-06-02 18:10   ` Rob Herring
2021-05-25  0:01 ` [PATCH v8 04/11] dt-bindings: drm/aux-bus: Add an example Douglas Anderson
2021-05-28  0:31   ` Linus Walleij
2021-06-02 18:16   ` Rob Herring
2021-06-02 19:55     ` Doug Anderson
2021-05-25  0:01 ` [PATCH v8 05/11] drm: Introduce the DP AUX bus Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 06/11] drm/panel: panel-simple: Allow panel-simple be a DP AUX endpoint device Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 07/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC Douglas Anderson
2021-06-04 16:10   ` rajeevny
2021-06-07 17:07     ` Doug Anderson
2021-05-25  0:01 ` [PATCH v8 08/11] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev Douglas Anderson
2021-06-06  4:40   ` Bjorn Andersson
2021-06-07 17:07     ` Doug Anderson
2021-05-25  0:01 ` [PATCH v8 09/11] drm/bridge: ti-sn65dsi86: Add support for the DP AUX bus Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 10/11] drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC Douglas Anderson
2021-05-25  0:01 ` [PATCH v8 11/11] arm64: dts: qcom: sc7180-trogdor: Move panel under the bridge chip Douglas Anderson

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