Re: [PATCH v5 2/3] drm/panel: Add support for S6E3HA2 panel driver on TM2 board

[Andrzej Hajda]

On 04.01.2017 15:44, Rob Herring wrote:
> On Wed, Jan 04, 2017 at 05:15:10PM +0900, Hoegeun Kwon wrote:
>> This patch add support for MIPI-DSI based S6E3HA2 AMOLED panel
>> driver. This panel has 1440x2560 resolution in 5.7-inch physical
>> panel in the TM2 device.
>>
>> Signed-off-by: Donghwa Lee <dh09.lee@xxxxxxxxxxx>
>> Signed-off-by: Hyungwon Hwang <human.hwang@xxxxxxxxxxx>
>> Signed-off-by: Hoegeun Kwon <hoegeun.kwon@xxxxxxxxxxx>
>> ---
>>  .../bindings/display/panel/samsung,s6e3ha2.txt     |  40 ++
>>  drivers/gpu/drm/panel/Kconfig                      |   6 +
>>  drivers/gpu/drm/panel/Makefile                     |   1 +
>>  drivers/gpu/drm/panel/panel-samsung-s6e3ha2.c      | 741 +++++++++++++++++++++
>>  4 files changed, 788 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/display/panel/samsung,s6e3ha2.txt
>>  create mode 100644 drivers/gpu/drm/panel/panel-samsung-s6e3ha2.c
>>
>> diff --git a/Documentation/devicetree/bindings/display/panel/samsung,s6e3ha2.txt b/Documentation/devicetree/bindings/display/panel/samsung,s6e3ha2.txt
>> new file mode 100644
>> index 0000000..6879f51
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/display/panel/samsung,s6e3ha2.txt
>> @@ -0,0 +1,40 @@
>> +Samsung S6E3HA2 5.7" 1440x2560 AMOLED panel
>> +
>> +Required properties:
>> +  - compatible: "samsung,s6e3ha2"
>> +  - reg: the virtual channel number of a DSI peripheral
>> +  - vdd3-supply: I/O voltage supply
>> +  - vci-supply: voltage supply for analog circuits
>> +  - reset-gpios: a GPIO spec for the reset pin (active low)
>> +  - enable-gpios: a GPIO spec for the panel enable pin (active high)
>> +  - te-gpios: a GPIO spec for the tearing effect synchronization signal
>> +    gpio pin (active high)
>> +
>> +The device node can contain one 'port' child node with one child
>> +'endpoint' node, according to the bindings defined in [1]. This
>> +node should describe panel's video bus.
>> +
>> +[1]: Documentation/devicetree/bindings/media/video-interfaces.txt
>> +
>> +Example:
>> +
>> +&dsi {
>> +	...
>> +
>> +	panel@0 {
>> +		compatible = "samsung,s6e3ha2";
>> +		reg = <0>;
>> +		vdd3-supply = <&ldo27_reg>;
>> +		vci-supply = <&ldo28_reg>;
>> +		reset-gpios = <&gpg0 0 GPIO_ACTIVE_LOW>;
>> +		enable-gpios = <&gpf1 5 GPIO_ACTIVE_HIGH>;
>> +		te-gpios = <&gpf1 3 GPIO_ACTIVE_HIGH>;
>> +
>> +		port {
>> +			panel_in: endpoint {
>> +				remote-endpoint = <&dsi_out>;
> As I said previously, it makes no sense to have a graph to dsi_out it is 
> simply the parent node.

The problem is that exynos_dsi requires presence of endpoint node, when
it was written the policy was that graphs must be always present.
DSI reads from this node samsung,burst-clock-frequency and
samsung,esc-clock-frequency. For example in exynos4412-trats2.dts:

>         dsi_0: dsi@11C80000 {
>                 ...
>                 ports {
>                         #address-cells = <1>;
>                         #size-cells = <0>;
>  
>                         port@1 {
>                                 reg = <1>;
>
>                                 dsi_out: endpoint {
>                                         remote-endpoint = <&dsi_in>;
>                                         samsung,burst-clock-frequency
> = <500000000>;
>                                         samsung,esc-clock-frequency =
> <20000000>;
>                                 };
>                         };
>                 };
>         
>                 panel@0 {
>                         ...
>                         port {
>                                 dsi_in: endpoint {
>                                         remote-endpoint = <&dsi_out>;
>                                 };
>                         };
>                 };
>         };

However, DSI driver does not use remote-endpoint property, it is here
only to fulfill of_graph policy.
So if something like below is acceptable, we can get rid of port node in
panel:

>         dsi_0: dsi@11C80000 {
>                 ...
>                 ports {
>                         #address-cells = <1>;
>                         #size-cells = <0>;
>  
>                         port@1 {
>                                 reg = <1>;
>
>                                 dsi_out: endpoint {
>                                         samsung,burst-clock-frequency
> = <500000000>;
>                                         samsung,esc-clock-frequency =
> <20000000>;
>                                 };
>                         };
>                 };
>         
>                 panel@0 {
>                         ...
>                 };
>         };

What do you think?

Other solution is to move problematic properties somewhere else, but
this require change of bindings.
Anyway I would be glad to remove port nodes in other samsung panels:
s6e8aa0, ld9040.

Regards
Andrzej