Re: [RFC 1/2] arm64: dts: qcom: x1e78100-t14s: Add LCD variant with backlight support

[Sebastian Reichel]

Hi,

On Thu, Mar 06, 2025 at 11:05:02AM +0200, Abel Vesa wrote:
> Due to the fact that Lenovo Thinkpad T14s Gen6 is available with both
> OLED and LCD, the backlight control differs HW-wise. For the LCD variant,
> the panel's backlight is controlled via one of the PWMs provided by the
> PMK8550 PMIC. For the OLED variant, the backlight is internal to the
> panel and therefore it is not described in devicetree.
> 
> For this reason, create a generic dtsi for the T14s by renaming the
> existing dts. While at it, add a node name to panel and drop the enable
> gpio and pinctrl properties from the panel node. Then add the LCD variant
> dts file with the old name and describe all backlight related nodes.
> 
> So the existing dts will now be used for LCD variant while for OLED new
> dts will be added.
> 
> Signed-off-by: Abel Vesa <abel.vesa@xxxxxxxxxx>
> ---
> [...]
> +	backlight: backlight {
> +		compatible = "pwm-backlight";
> +		pwms = <&pmk8550_pwm 0 5000000>;

I've tried this patch series together with the fix series [0], but
without the duty cycle calculation change [1]. Instead I changed the
period from 5000000 to 4266667. With that everything works as
expected for me.

[0] https://lore.kernel.org/all/20250305-leds-qcom-lpg-fix-max-pwm-on-hi-res-v4-0-bfe124a53a9f@xxxxxxxxxx/
[1] https://lore.kernel.org/all/20250303-leds-qcom-lpg-compute-pwm-value-using-period-v1-1-833e729e3da2@xxxxxxxxxx/

Greetings,

-- Sebastian

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