Re: [PATCH v2 2/4] dt-bindings: display: bridge: add it66121 bindings

Neil Armstrong
2020-03-13T14:12:22Z

On 13/03/2020 14:40, Laurent Pinchart wrote:
> Hi Phong,
>
> Thank you for the patch.
>
> On Wed, Mar 11, 2020 at 01:51:33PM +0100, Phong LE wrote:
>> Add the ITE bridge HDMI it66121 bindings.
>>
>> Signed-off-by: Phong LE <ple@baylibre.com>
>> ---
>> .../bindings/display/bridge/ite,it66121.yaml | 98 +++++++++++++++++++
>> 1 file changed, 98 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/display/bridge/ite,it66121.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/display/bridge/ite,it66121.yaml b/Documentation/devicetree/bindings/display/bridge/ite,it66121.yaml
>> new file mode 100644
>> index 000000000000..1717e880d130
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/display/bridge/ite,it66121.yaml
>> @@ -0,0 +1,98 @@
>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/display/bridge/ite,it66121.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: ITE it66121 HDMI bridge Device Tree Bindings
>> +
>> +maintainers:
>> + - Phong LE <ple@baylibre.com>
>> + - Neil Armstrong <narmstrong@baylibre.com>
>> +
>> +description: |
>> + The IT66121 is a high-performance and low-power single channel HDMI
>> + transmitter, fully compliant with HDMI 1.3a, HDCP 1.2 and backward compatible
>> + to DVI 1.0 specifications.
>> +
>> +properties:
>> + compatible:
>> + const: ite,it66121
>> +
>> + reg:
>> + maxItems: 1
>> + description: base I2C address of the device
>> +
>> + reset-gpios:
>> + maxItems: 1
>> + description: GPIO connected to active low reset
>> +
>> + vrf12-supply:
>> + maxItems: 1
>> + description: Regulator for 1.2V analog core power.
>> +
>> + vcn33-supply:
>> + maxItems: 1
>> + description: Regulator for 3.3V digital core power.
>> +
>> + vcn18-supply:
>> + maxItems: 1
>> + description: Regulator for 1.8V IO core power.
>> +
>> + interrupts:
>> + maxItems: 1
>> +
>> + pclk-dual-edge:
>> + maxItems: 1
>> + description: enable pclk dual edge mode.
>
> I'm having a bit of trouble understanding how this operates. Looking at
> the driver code the property is only taken into account to calculate the
> maximum allowed frequency. How is the IT66121 configured for single vs.
> dual pixel clock edge mode ?

Dual edge mode is Dual-Data-Rate mode, the normal mode is MEDIA_BUS_FMT_RGB888_1X24 and dual edge is
MEDIA_BUS_FMT_RGB888_2X12_LE (or MEDIA_BUS_FMT_RGB888_2X12_BE, not sure) on a single clock period.

This should be negociated at runtime, but the bus width should be specified somewhere to select
one of the modes.

Neil

>
>> +
>> + port:
>> + type: object
>> +
>> + properties:
>> + endpoint:
>> + type: object
>> + description: |
>> + Input endpoints of the bridge.
>> +
>> + required:
>> + - endpoint
>
> You should have two ports, one for the bridge input, and one for the
> bridge output.
>
>> +
>> +required:
>> + - compatible
>> + - reg
>> + - reset-gpios
>> + - vrf12-supply
>> + - vcn33-supply
>> + - vcn18-supply
>> + - interrupts
>> + - port
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> + - |
>> + i2c6 {
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> +
>> + it66121hdmitx: it66121hdmitx@4c {
>> + compatible = "ite,it66121";
>> + pinctrl-names = "default";
>> + pinctrl-0 = <&ite_pins_default>;
>> + vcn33-supply = <&mt6358_vcn33_wifi_reg>;
>> + vcn18-supply = <&mt6358_vcn18_reg>;
>> + vrf12-supply = <&mt6358_vrf12_reg>;
>> + reset-gpios = <&pio 160 1 /* GPIO_ACTIVE_LOW */>;
>> + interrupt-parent = <&pio>;
>> + interrupts = <4 8 /* IRQ_TYPE_LEVEL_LOW */>;
>> + reg = <0x4c>;
>> + pclk-dual-edge;
>> +
>> + port {
>> + it66121_in: endpoint {
>> + remote-endpoint = <&display_out>;
>> + };
>> + };
>> + };
>> + };
>