On Mon, May 07, 2018 at 10:15:46PM +0200, Paul Kocialkowski wrote:
- 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>;The increase in perceived brightness should be linear. Usually, for PWMs backed backlight, an exponential list is a much better approximation.
Thanks for the hint, it never occurred to me that pwm duty cycle was not linear with brightness, but that makes sense. I'll give that a try (on 255 values instead of 10 to keep some level of precision in low brightness). The way to go here is probably use a base-255 logarithm such as: duty cycle = range * log(i+1)/log(255) with i the linear brightness value (0 to 255) and range the amplitude of our values (that gets divided by the maximum brightness, so it's really up to hardware precision at this point). I'll go with a range of 255 as well.
Without going into something so complicated, usually a list with power of two ending at 255 is a good approximation :)
+&mmc0 {
- pinctrl-names = "default";
- pinctrl-0 = <&mmc0_pins_a>;
- vmmc-supply = <®_vcc3v3>;
You have the regulators described in your DT, you'd better use them instead of the one coming from sunxi-common-regulators.dtsi.
Well, according to the reference A20 design, the mmc pins and the card are powered by the 3.3V power rail, that comes from a regular step-down regulator sourcing from IPSOUT, so I don't see what regulator I should better use. Do you have a suggestion?
That works for me then.
+&pio {
- panel_power_pin: panel_power_pin@0 {
pins = "PH8";function = "gpio_out";- };
+};
You don't need that pinctrl node.
I'll get rid of it then. You mentioned that regulator-simple uses the old GPIO API, so I assumed it meant that a pinctrl node is still needed. For reference, it uses of_get_named_gpio (not the devm-managed fashion).
This is only relevant for the polarity of the pins, not the pinctrl part.
Maxime