[linux-sunxi] Re: [PATCH 5/5] ARM: dts: sun5i: Add backlight node to sun5i-q8-common.dtsi

Hi,

On 09/20/2015 11:14 AM, Hans de Goede wrote:

Hi,

On 09/20/2015 10:46 AM, Chen-Yu Tsai wrote:

quoted

On Sun, Sep 20, 2015 at 8:30 PM, Hans de Goede [off-list ref] wrote:

quoted

All A13 based q8 formfactor tablets use the same backlight setup, add
a backlight devicetree node for controlling the backlight on these devices.

Signed-off-by: Hans de Goede <redacted>
---
  arch/arm/boot/dts/sun5i-q8-common.dtsi | 11 +++++++++++
  1 file changed, 11 insertions(+)

diff --git a/arch/arm/boot/dts/sun5i-q8-common.dtsi b/arch/arm/boot/dts/sun5i-q8-common.dtsi
index 0641d68..76a5204 100644
--- a/arch/arm/boot/dts/sun5i-q8-common.dtsi
+++ b/arch/arm/boot/dts/sun5i-q8-common.dtsi

@@ -41,11 +41,22 @@
   */
  #include "sunxi-q8-common.dtsi"

+#include <dt-bindings/pwm/pwm.h>
+
  / {
         aliases {
                 serial0 = &uart1;
         };

+       backlight: backlight {
+               compatible = "pwm-backlight";
+               pwms = <&pwm 0 50000 PWM_POLARITY_INVERTED>;
+               brightness-levels = <0 10 20 30 40 50 60 70 80 90 100>;
+               default-brightness-level = <8>;
+               /* TODO: backlight uses axp gpio1 as enable pin */
+               /* TODO: backlight is powered by AXP209 DCDC1SW */

There's no DCDC1SW on AXP209. The reference design shows the backlight
regulator is powered directly from IPSOUT,

Ah, right, I'll do a v2 dropping this comment line.

 > but the PWM pullup is powered

quoted

by LCD-VCC,  which itself is enabled by AXP209 GPIO0.

Would that be the case, or maybe closer, given we don't have schematics?

gpio0 needs to be driven high to get the backlight to lite up, that
is pretty much all I know.

Correction, gpio1. I guess that pullup is only there to keep the backlight
off while the pwm pin is still muxed as input, rather then pwm-output.

Regards,

Hans