[PATCH 1/3 v3] drm/panel: Add generic DSI panel YAML bindings

Linus Walleij linus.walleij at linaro.org
Fri Oct 18 18:24:44 UTC 2019

This adds a starting point for processing and defining generic
bindings used by DSI panels. We just define one single bool
property to force the panel into video mode for now.

Cc: devicetree at vger.kernel.org
Suggested-by: Rob Herring <robh at kernel.org>
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
ChangeLog v2->v3:
- Make a more complete DSI panel binding including the controller
  and its address-cells and size-cells and a pattern for the panel
  nodes. The panel is one per DSI master, the reg property is
  compulsory but should always be 0 (as far as I can tell) as
  only one panel can be connected. The bus doesn't really have
  any addresses for the panel, the address/reg notation seems
  to be cargo-culted from the port graphs and is not necessary
  to parse some device trees, it is used to tell whether the
  node is a panel or not rather than any addressing.
- I have no idea how many displays you can daisychain on a single
  DSI master, I just guess 15 will be enough. The MIPI-specs
  are memberwalled. Someone who knows can tell perhaps?
ChangeLog v1->v2:
- New patch after feedback.
 .../display/panel/panel-dsi-common.yaml       | 58 +++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/panel/panel-dsi-common.yaml

diff --git a/Documentation/devicetree/bindings/display/panel/panel-dsi-common.yaml b/Documentation/devicetree/bindings/display/panel/panel-dsi-common.yaml
new file mode 100644
index 000000000000..d63f597eff9c
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/panel/panel-dsi-common.yaml
@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+$id: http://devicetree.org/schemas/display/panel/panel-dsi-common.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+title: Common Properties for DSI Display Panels
+  - Linus Walleij <linus.walleij at linaro.org>
+description: |
+  This document defines device tree properties common to DSI, Display
+  Serial Interface panels. It doesn't constitute a device tree binding
+  specification by itself but is meant to be referenced by device tree
+  bindings.
+  When referenced from panel device tree bindings the properties defined in
+  this document are defined as follows. The panel device tree bindings are
+  responsible for defining whether each property is required or optional.
+  Notice: this binding concerns DSI panels connected directly to a master
+  without any intermediate port graph to the panel. Each DSI master
+  can control exactly one panel. They should all just have a node "panel"
+  for their panel with their reg-property set to 0.
+  $nodename:
+    pattern: "^dsi-controller(@[0-9a-f]+)?$"
+  "#address-cells":
+    const: 1
+  "#size-cells":
+    const: 0
+  "^panel$":
+    type: object
+    properties:
+      reg:
+        const: 0
+        description:
+          Only one panel can be connected to each DSI controller, but for
+          historical reasons, the reg property must be specified, as the
+          DSI controller can contain other child nodes, and operating
+          systems will identify which child node is the panel by looking
+          for the reg property. It should however always be set to 0.
+      enforce-video-mode:
+        type: boolean
+        description:
+          The best option is usually to run a panel in command mode, as this
+          gives better control over the panel hardware. However for different
+          reasons like broken hardware, missing features or testing, it may be
+          useful to be able to force a command mode-capable panel into video
+          mode.

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