On Thu, Sep 27, 2018 at 10:47 PM Maxime Ripard
[off-list ref] wrote:

On Thu, Sep 27, 2018 at 05:18:50PM +0530, Jagan Teki wrote:

quoted

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 at 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 ...