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From: Rob Herring <robh@kernel.org>
To: Douglas Anderson <dianders@chromium.org>
Cc: Neil Armstrong <narmstrong@baylibre.com>,
	David Airlie <airlied@linux.ie>,
	dri-devel@lists.freedesktop.org,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Andrzej Hajda <a.hajda@samsung.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Sam Ravnborg <sam@ravnborg.org>,
	robdclark@chromium.org,
	Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>,
	Thierry Reding <treding@nvidia.com>,
	devicetree@vger.kernel.org, Jonas Karlman <jonas@kwiboo.se>,
	linux-arm-msm@vger.kernel.org, Stephen Boyd <swboyd@chromium.org>,
	Rob Herring <robh+dt@kernel.org>,
	Steev Klimaszewski <steev@kali.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple
Date: Wed, 2 Jun 2021 13:00:17 -0500	[thread overview]
Message-ID: <20210602180017.GA3674744@robh.at.kernel.org> (raw)
In-Reply-To: <20210524165920.v8.1.Ieb731d23680db4700cc41fe51ccc73ba0b785fb7@changeid>

On Mon, 24 May 2021 17:01:49 -0700, Douglas Anderson wrote:
> 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(+)
> 

Reviewed-by: Rob Herring <robh@kernel.org>

  reply	other threads:[~2021-06-02 18:00 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 ` [PATCH v8 01/11] dt-bindings: display: simple: List hpd properties in panel-simple Douglas Anderson
2021-06-02 18:00   ` Rob Herring [this message]
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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