linux-kernel - Re: [PATCH v1 1/1] arm64: dts: qcom: talos-evk: Add support for dual-channel LVDS panel

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Message-ID: <sfxvtfzzstdbt7in6z6ztsjfy6e555fr3sjbi5kqkv5sk77b26@kl57zs7iuuvk>
Date: Wed, 29 Oct 2025 14:34:57 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Tessolve Upstream <tessolveupstream@...il.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>, andersson@...nel.org,
        konradybcio@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
        conor+dt@...nel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] arm64: dts: qcom: talos-evk: Add support for
 dual-channel LVDS panel

On Wed, Oct 29, 2025 at 05:50:01PM +0530, Tessolve Upstream wrote:
> 
> 
> On 28/10/25 14:55, Konrad Dybcio wrote:
> > On 10/28/25 7:16 AM, Sudarshan Shetty wrote:
> >> This patch introduces a new device tree for the QCS615 Talos
> >> EVK platform with dual-channel LVDS display support.
> >>
> >> The new DTS file (`talos-evk-lvds.dts`) is based on the existing
> >> `talos-evk.dts` and extends it to enable a dual-channel LVDS display
> >> configuration using the TI SN65DSI84 DSI-to-LVDS bridge.
> >>
> >> where channel-A carries odd pixel and channel-B carries even pixel
> >> on the QCS615 talos evk platform.
> >>
> >> Signed-off-by: Sudarshan Shetty <tessolveupstream@...il.com>
> >> ---
> > 
> > [...]
> > 
> >> +	backlight: backlight {
> >> +		compatible = "gpio-backlight";
> >> +		gpios = <&tlmm 115 GPIO_ACTIVE_HIGH>;
> >> +		default-on;
> >> +	};
> >> +
> >> +	lcd0_pwm_en {
> > 
> > Use hyphens instead of underscores in node names
> 
> Okay, will update in next patch.
> > 
> >> +		compatible = "pwm-gpio";
> >> +		gpios = <&tlmm 59 GPIO_ACTIVE_HIGH>;
> >> +		pinctrl-0 = <&lcd0_bklt_pwm>;
> > 
> > I think your intention was to use pwm-backlight and wire this node
> > up to that
> 
> Soc does not support the PWM interface hence we are using gpio 
> as "pwm-gpio" by setting the duty cycle to 100%(i.e. "no pwm")

Why do you mention PWM here at all? It's perfectly fine to use
gpio-backlight. That looks extremely suspicious since you are not
referecing the pwm-gpio device at all.

-- 
With best wishes
Dmitry