On Thu, Oct 04, 2018 at 09:33:59PM +0530, Jagan Teki wrote:
> On Thu, Sep 27, 2018 at 10:47 PM Maxime Ripard
> <maxime.ripard@bootlin.com> wrote:
> >
> > On Thu, Sep 27, 2018 at 05:18:50PM +0530, Jagan Teki wrote:
> > > This patch add support for Bananapi S070WV20-CT16 DSI panel to
> > > BPI-M64 board.
> > >
> > > DSI panel connected via board DSI port with,
> > > - DC1SW as AVDD supply
> > > - DCDC1 as DVDD supply
> > > - PD6 gpio for reset pin
> > > - PD5 gpio for backlight enable pin
> > > - PD7 gpio for backlight vdd supply
> > >
> > > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > > ---
> > >  .../dts/allwinner/sun50i-a64-bananapi-m64.dts | 42 +++++++++++++++++++
> > >  1 file changed, 42 insertions(+)
> > >
> > > diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64-bananapi-m64.dts b/arch/arm64/boot/dts/allwinner/sun50i-a64-bananapi-m64.dts
> > > index ef1c90401bb2..c0be949be68d 100644
> > > --- a/arch/arm64/boot/dts/allwinner/sun50i-a64-bananapi-m64.dts
> > > +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64-bananapi-m64.dts
> > > @@ -45,6 +45,7 @@
> > >  #include "sun50i-a64.dtsi"
> > >
> > >  #include <dt-bindings/gpio/gpio.h>
> > > +#include <dt-bindings/pwm/pwm.h>
> > >
> > >  / {
> > >       model = "BananaPi-M64";
> > > @@ -56,6 +57,24 @@
> > >               serial1 = &uart1;
> > >       };
> > >
> > > +     vdd_bl: regulator@0 {
> > > +             compatible = "regulator-fixed";
> > > +             regulator-name = "bl-3v3";
> > > +             regulator-min-microvolt = <3300000>;
> > > +             regulator-max-microvolt = <3300000>;
> > > +             gpio = <&pio 3 7 GPIO_ACTIVE_HIGH>; /* PD7 */
> > > +             enable-active-high;
> > > +     };
> > > +
> > > +     backlight_dsi: backlight-dsi {
> > > +             compatible = "pwm-backlight";
> > > +             pwms = <&r_pwm 0 50000 PWM_POLARITY_INVERTED>;
> > > +             brightness-levels = <0 10 20 30 40 50 60 70 80 90 100>;
> >
> > The brightness levels should be increasing linearly from a user point
> > of view. Usually, with a PWM backlight, a quadratic rule works much
> > better.
> 
> Does that mean, 0 40 80 ...

No, that means 1 2 4 8 16 32 etc..

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com