On 15.01.2018 22:27, Andy Shevchenko wrote:
> On Mon, Jan 15, 2018 at 10:41 AM, Claudiu Beznea
> <Claudiu.Beznea@xxxxxxxxxxxxx> wrote:
>
>> 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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