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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>,
	Thierry Reding <thierry.reding@gmail.com>,
	dri-devel@lists.freedesktop.org,
	Stephen Boyd <swboyd@chromium.org>,
	Thierry Reding <treding@nvidia.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple
Date: Mon, 24 May 2021 17:01:49 -0700	[thread overview]
Message-ID: <20210524165920.v8.1.Ieb731d23680db4700cc41fe51ccc73ba0b785fb7@changeid> (raw)
In-Reply-To: <20210525000159.3384921-1-dianders@chromium.org>

The HPD (Hot Plug Detect) signal is present in many (probably even
"most") eDP panels. For eDP, this signal isn't actually used for
detecting hot-plugs of the panel but is more akin to a "panel ready"
signal. After you provide power to the panel, panel timing diagrams
typically say that you should wait for HPD to be asserted (or wait a
fixed amount of time) before talking to the panel.

The panel-simple bindings describes many eDP panels and many of these
panels provide the HPD signal. We should add the HPD-related
properties to the panel-simple bindings. The HPD properties are
actually defined in panel-common.yaml, so adding them here just
documents that they are OK for panels handled by the panel-simple
bindings.

NOTE: whether or not we'd include HPD properties in the panel node is
more a property of the board design than the panel itself. For most
boards using these eDP panels everything "magically" works without
specifying any HPD properties and that's been why we haven't needed to
allow the HPD properties earlier. On these boards the HPD signal goes
directly to a dedicated "HPD" input to the eDP controller and this
connection doesn't need to be described in the device tree. The only
time the HPD properties are needed in the device tree are if HPD is
hooked up to a GPIO or if HPD is normally on the panel but isn't used
on a given board. That means that if we don't allow the HPD properties
in panel-simple then one could argue that we've got to boot all eDP
panels (or at least all those that someone could conceivably put on a
system where HPD goes to a GPIO or isn't hooked up) from panel-simple.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v8:
- Explain better why HPD needs to be in panel-simple in commit msg.

Changes in v7:
- List hpd properties bindings patch new for v7.

 .../devicetree/bindings/display/panel/panel-simple.yaml         | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
index b3797ba2698b..4a0a5e1ee252 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
+++ b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
@@ -298,6 +298,8 @@ properties:
   enable-gpios: true
   port: true
   power-supply: true
+  no-hpd: true
+  hpd-gpios: true
 
 additionalProperties: false
 
-- 
2.31.1.818.g46aad6cb9e-goog


  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 the DP AUX bus Douglas Anderson
2021-05-25  0:01 ` Douglas Anderson [this message]
2021-06-02 18:00   ` [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple Rob Herring
2021-05-25  0:01 ` [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus Douglas Anderson
2021-06-02 18:08   ` 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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