Re: [PATCH v2 2/4] arm64: dts: qcom: shikra-cqm-evk: Enable display and add ili7807s panel

[Dmitry Baryshkov]

On Fri, Jul 10, 2026 at 02:10:48PM +0200, Konrad Dybcio wrote:
> On 7/10/26 1:58 PM, Arpit Saini wrote:
> > Hi Konrad,
> > 
> > On 7/10/2026 2:31 PM, Arpit Saini wrote:
> >> Hi Konrad,
> >>
> >> On 7/6/2026 3:33 PM, Konrad Dybcio wrote:
> >>> On 7/6/26 8:04 AM, Nabige Aala wrote:
> >>>> From: Arpit Saini <arpit.saini@xxxxxxxxxxxxxxxx>
> 
> [...]
> 
> >>>> +    panel_bl_en_suspend: panel-bl-en-suspend-state {
> >>>> +        pins = "gpio91";
> >>>> +        function = "gpio";
> >>>> +        drive-strength = <2>;
> >>>> +        bias-pull-down;
> >>>> +        output-low;
> >>>> +    };
> >>> output-foo isn't necessary, the panel driver will assert it as
> >>> necessary
> >>>
> >>> Konrad
> >>
> >> Ack, thanks for pointing out.
> >>
> >> Arpit
> >>
> > I just checked,
> > 
> > Normally the backlight EN pin is controlled by a backlight driver.
> > 
> > However, this panel uses MIPI DCS based backlight control with no
> > 
> > separate backlight driver. Since there is no driver to assert gpio91,
> > 
> > we control it via the panel's pinctrl default state..
> > 
> > So this is platform specific pin , we need this to enable/disable
> > 
> > the backlight.
> 
> Why would the backlight state be so tightly defined by the panel?
> Disabling or adjusting the backlight level without shutting down
> the panel is a perfectly valid use case.
> 
> Take a look at pwm-backlight or gpio-backlight.

This one is different. The backlight is controlled over the DSI link. In
this case there is no separate driver for the backlight, the panel
driver handles it (it needs to be like this for multiple reasons).

-- 
With best wishes
Dmitry