[U-Boot] [PATCH 2/4] video: tegra: Move to using simple-panel and pwm-backlight

[Stephen Warren]

On 01/14/2016 01:26 PM, Simon Glass wrote:
> We have standard drivers for panels and backlights which can do most of the
> work for us. Move the tegra20 LCD driver over to use those instead of custom
> code.
>
> This patch includes device tree changes for the nvidia boards. I have only
> been able to test seaboard. If this patch is applied, these boards will
> also need to be synced with the kernel, and updated to use display-timings:
>
>     - colibri
>     - medcom-wide
>     - paz00
>     - tec

> diff --git a/arch/arm/dts/tegra20-harmony.dts b/arch/arm/dts/tegra20-harmony.dts

This file has huge changes unrelated to panel, video, and backlight. 
Perhaps patch 1/4 was meant to sync the DTs for Harmony and Ventana too 
rather than just Seaboard, leaving this commit to make roughly identical 
DT changes for all 3 boards?

> diff --git a/arch/arm/dts/tegra20-seaboard.dts b/arch/arm/dts/tegra20-seaboard.dts

> +
> +				display-timings {
> +					timing at 0 {
> +						/* Seaboard has 1366x768 */
> +						clock-frequency = <70600000>;
> +						hactive = <1366>;
> +						vactive = <768>;
> +						hback-porch = <58>;
> +						hfront-porch = <58>;
> +						hsync-len = <58>;
> +						vback-porch = <4>;
> +						vfront-porch = <4>;
> +						vsync-len = <4>;
> +						hsync-active = <1>;
> +					};
> +				};

It seems very strange to go to the effort of creating patch 1 to sync 
the U-Boot and Linux DT files (such that I assume they're 100% 
identical?) yet immediately have patch 2 diverge the two DTs again.

This lends more weight to my argument that the U-Boot DTs should contain 
only nodes that U-Boot actively uses. I can see the argument for copying 
over the entire DT from Linux into U-Boot in order to keep them 100% 
identical, and in turn that means importing a bunch of DT content that 
U-Boot doesn't use. However, that argument completely breaks down if the 
DTs are just going to diverge still.

At least the display-timings node is a standard binding, even if it 
isn't one that the Linux Tegra DTs make use of.

> diff --git a/configs/harmony_defconfig b/configs/harmony_defconfig
> index 14125b4..0de56a9 100644
> --- a/configs/harmony_defconfig
> +++ b/configs/harmony_defconfig
> @@ -12,9 +12,11 @@ CONFIG_SYS_PROMPT="Tegra20 (Harmony) # "
>   CONFIG_CMD_GPIO=y
>   # CONFIG_CMD_SETEXPR is not set
>   # CONFIG_CMD_NFS is not set
> +CONFIG_CMD_PMIC=y
> +CONFIG_CMD_REGULATOR=y
>   CONFIG_DM_PMIC=y
>   CONFIG_DM_REGULATOR=y
> -CONFIG_DM_PWM=y
> +CONFIG_DM_REGULATOR_FIXED=y
>   CONFIG_PWM_TEGRA=y
>   CONFIG_SYS_NS16550=y
>   CONFIG_USB=y
> @@ -22,3 +24,4 @@ CONFIG_DM_USB=y
>   CONFIG_DM_VIDEO=y
>   CONFIG_VIDEO_TEGRA20=y
>   CONFIG_USE_PRIVATE_LIBGCC=y
> +CONFIG_ERRNO_STR=y

I assume those are all needed by the modified Tegra video/LCD driver. If 
so, wouldn't it make sense for that driver to select those Kconfig 
options rather than requiring every board defconfig to be modified to 
enable the features?