Re: [PATCH v2 01/16] drivers: pwm: core: use a single of xlate function

On 15.01.2018 22:27, Andy Shevchenko wrote:

On Mon, Jan 15, 2018 at 10:41 AM, Claudiu Beznea
[off-list ref] wrote:

quoted

For this driver, the PWM bindings were changed (I did a grep by "google,cros-ec-pwm"
and located only:
arch/arm64/boot/dts/rockchip/rk3399-gru-kevin.dts
arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi
files) and changed the bindings in this series, as follows, patch 7 from this series:

diff --git a/arch/arm64/boot/dts/rockchip/rk3399-gru-kevin.dts b/arch/arm64/boot/dts/rockchip/rk3399-gru-kevin.dts
index 0384e3121f18..0c790ec387eb 100644
--- a/arch/arm64/boot/dts/rockchip/rk3399-gru-kevin.dts
+++ b/arch/arm64/boot/dts/rockchip/rk3399-gru-kevin.dts

@@ -77,7 +77,7 @@

        backlight: backlight {
                compatible = "pwm-backlight";
-               pwms = <&cros_ec_pwm 1>;
+               pwms = <&cros_ec_pwm 1 65535>;

This shows an breakage for user.

As long as pwm-cells=2 the OF hooks will read PWM channel and PWM period
(e.g. in this case, PWM channel=1, PWM period=65532)
I don't see a breakage here. Please explain me further.

The old PWM device tree sources or

binaries should work independently on what changes you did to kernel.

Please explain me further. From this I understand, as a general rule,
that the device tree binaries from, e.g. 3 years ago, should be
compatible with, e.g. the current version of kernel?

Thanks,
Claudiu

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