Re: [PATCH 3/3] drm/panel: himax-hx83121a: add backlight regulator support

[Pengyu Luo]

On Thu, Jun 11, 2026 at 1:43 PM Icenowy Zheng <zhengxingda@xxxxxxxxxxx> wrote:
>
> 在 2026-06-11四的 13:26 +0800，Pengyu Luo写道：
> > On Tue, 09 Jun 2026 00:26:22 +0800, Icenowy Zheng
> > <zhengxingda@xxxxxxxxxxx> wrote:
> > > diff --git a/drivers/gpu/drm/panel/panel-himax-hx83121a.c
> > > b/drivers/gpu/drm/panel/panel-himax-hx83121a.c
> > > index 1a7e0125bced..e31e2fba0a78 100644
> > > --- a/drivers/gpu/drm/panel/panel-himax-hx83121a.c
> > > +++ b/drivers/gpu/drm/panel/panel-himax-hx83121a.c
> > > @@ -195,7 +197,27 @@ static int himax_bl_update_status(struct
> > > backlight_device *bl)
> > > [ ... skip 18 lines ... ]
> > > +           ret = regulator_enable(ctx->bl_supply);
> > > +   if (ret)
> > > +           return ret;
> > > +
> > > +   ctx->backlight_enabled = true;
> > > +
> >
> > If you use a pin, (it is indeed a hwen pin as we know) you can
> > simplify it like this,
> >
> > bool bl_enable_now = !!brightness;
> >
> > if (ctx->bl_enable != bl_enable_now) {
> >       gpiod_set_value(ctx->hwen_gpio, bl_enable_now);
> >       ctx->bl_enable = bl_enable_now;
> > }
> >
> > BTW, iirc, panel bias can be turned off too, although I don't think
> > this will save too much power.
>
> BTW during my test, it seems that DCS backlight 0 isn't turning off
> backlight.
>

Yes, there is a hwen pin to turn off BL. In the downstream, I added
it, no time to upstream it, I forgot to add display DT too. I meant
you can turn off panel bias too, if you turn off BL. In general, I
turn off it in drm_panel_unprepare()

Best wishes,
Pengyu