Re: [PATCH 19/25] ARM: tegra: Add dummy backlight power supplies

[Dmitry Osipenko <digetx@gmail.com>]

09.12.2021 20:33, Thierry Reding пишет:
> From: Thierry Reding <treding@nvidia.com>
> 
> The Medcom Wide and PAZ00 boards don't specify the power supply for the
> backlight, which means that the Linux driver will provide a dummy one.
> Wire up an explicit dummy to also make the DT schema validation succeed.
> Unfortunately I don't have access to the schematics for these boards, so
> I don't know if a more accurate description is possible.
> 
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---
>  arch/arm/boot/dts/tegra20-medcom-wide.dts | 3 +++
>  arch/arm/boot/dts/tegra20-paz00.dts       | 3 +++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/tegra20-medcom-wide.dts b/arch/arm/boot/dts/tegra20-medcom-wide.dts
> index ed0e4012e140..b072d715999e 100644
> --- a/arch/arm/boot/dts/tegra20-medcom-wide.dts
> +++ b/arch/arm/boot/dts/tegra20-medcom-wide.dts
> @@ -54,6 +54,9 @@ backlight: backlight {
>  
>  		brightness-levels = <0 4 8 16 32 64 128 255>;
>  		default-brightness-level = <6>;
> +
> +		/* dummy */
> +		power-supply = <&vdd_5v0_reg>;
>  	};
>  
>  	panel: panel {
> diff --git a/arch/arm/boot/dts/tegra20-paz00.dts b/arch/arm/boot/dts/tegra20-paz00.dts
> index e4c6c1363fc5..dd80108ac72c 100644
> --- a/arch/arm/boot/dts/tegra20-paz00.dts
> +++ b/arch/arm/boot/dts/tegra20-paz00.dts
> @@ -571,6 +571,9 @@ backlight: backlight {
>  
>  		brightness-levels = <0 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 255>;
>  		default-brightness-level = <10>;
> +
> +		/* dummy */
> +		power-supply = <&p5valw_reg>;
>  	};
>  
>  	clk32k_in: clock-32k {
> 

I think David's patches should be more correct [1][2]. Very unlikely
that 5v is used directly for backlight. I looked at the AC100 patch
previously, checking schematics. You can download paz00 schematics from
the internet [3].

[1]
https://github.com/okias/linux/commit/0a24a3097b2dcb6bb81b13197a2d4836f858199e

[2]
https://github.com/okias/linux/commit/98a2a32c482d0ffd59d96d22ae4169cc3d0ff15d

[3]
https://www.s-manuals.com/pdf/motherboard/compal/compal_la-6352p_r1.0a_schematics.pdf