Re: [PATCH 1/3 v4] drm/panel: Add generic DSI panel YAML bindings

On Thu, Oct 24, 2019 at 01:43:03PM +0200, Linus Walleij wrote:

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@vger.kernel.org Suggested-by: Rob Herring robh@kernel.org Signed-off-by: Linus Walleij linus.walleij@linaro.org

---

ChangeLog v3->v4:

• Rename into display/dsi-controller.yaml
• Require a virtual channel number for the DSI panel, as DSI have this 2-bit virtual address field.
• Bring in some but not all properties from the existing MIPI DSI bindings. This schema can be used with simpler panels but not complex panels with multiple virtual channels for the moment. Let's handle it when we get there.
• Add an example.

A broken example...

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.

---

.../bindings/display/dsi-controller.yaml | 88 +++++++++++++++++++ 1 file changed, 88 insertions(+) create mode 100644 Documentation/devicetree/bindings/display/dsi-controller.yaml

diff --git a/Documentation/devicetree/bindings/display/dsi-controller.yaml b/Documentation/devicetree/bindings/display/dsi-controller.yaml new file mode 100644 index 000000000000..2a6d872a40c5 --- /dev/null +++ b/Documentation/devicetree/bindings/display/dsi-controller.yaml @@ -0,0 +1,88 @@ +# 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

+maintainers:

• • Linus Walleij linus.walleij@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.

+properties:

• $nodename:
• pattern: "^dsi-controller(@.*)?$"
• "#address-cells":
• const: 1
• "#size-cells":
• const: 0

+patternProperties:

• "^panel@[0-3]$":
• type: object
• properties:

•  reg:
  

•    minimum: 0
  

•    maximum: 3
  

•    description:
  

•      The virtual channel number of a DSI peripheral. Must be in the range
  

•      from 0 to 3, as DSI uses a 2-bit addressing scheme. Some DSI
  

•      peripherals respond to more than a single virtual channel. In that
  

•      case the reg property can take multiple entries, one for each virtual
  

•      channel that the peripheral responds to.
  

•  clock-master:
  

•    type: boolean
  

•    description:
  

•       Should be enabled if the host is being used in conjunction with
  

•       another DSI host to drive the same peripheral. Hardware supporting
  

•       such a configuration generally requires the data on both the busses
  

•       to be driven by the same clock. Only the DSI host instance
  

•       controlling this clock should contain this property.
  

•  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.
  

• required:

•  - reg
  

+examples:

• • |
• dsi-controller@55aa55aa {

•  compatible = "acme,foo";
  

Eventually, I want to start reporting if compatible strings aren't documented (i.e. matched to a schema). This will break then...

•  reg = <0x55aa55aa>;
  

This will fail because a size cell is expected.

I'd just drop both properties here. A 'dsi-controller' node name is enough to select this schema.

•  #address-cells = <1>;
  

•  #size-cells = <0>;
  

•  panel@0 {
  

•    compatible = "acme,bar";
  

Just pick a real one. (Or drop the example because the binding for the real panel will have the same example).

•    reg = <0>;
  

•    vddi-supply = <&foo>;
  

•    reset-gpios = <&foo_gpio 0 GPIO_ACTIVE_LOW>;
  

•  };
  

• };

+...

2.21.0