Subject: Re: [PATCH v2 01/16] drivers: pwm: core: use a single of xlate
 function
To: Andy Shevchenko <andy.shevchenko@gmail.com>
CC: Brian Norris <briannorris@chromium.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Russell King - ARM Linux <linux@armlinux.org.uk>,
        Daniel Mack <daniel@zonque.org>,
        Haojian Zhuang <haojian.zhuang@gmail.com>,
        Robert Jarzmik <robert.jarzmik@free.fr>,
        Jonathan Corbet <corbet@lwn.net>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Alexandre Belloni <alexandre.belloni@free-electrons.com>,
        <linux-pwm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
        <linux-amlogic@lists.infradead.org>,
        <linux-rockchip@lists.infradead.org>,
        <linux-rpi-kernel@lists.infradead.org>,
        devicetree <devicetree@vger.kernel.org>,
        Mike Dunn <mikedunn@newsguy.com>,
        Alexander Shiyan <shc_work@mail.ru>
References: <1515766983-15151-1-git-send-email-claudiu.beznea@microchip.com>
 <1515766983-15151-2-git-send-email-claudiu.beznea@microchip.com>
 <20180112183512.GB102880@google.com>
 <6441df76-fb4a-ce00-1019-f7ff9143b75e@microchip.com>
 <CAHp75VcaFDEQ1cBzeU2eBj_vf19ok6EWLC07SOTQLRH8BQSbzA@mail.gmail.com>
From: Claudiu Beznea <Claudiu.Beznea@microchip.com>
Message-ID: <9a130c0b-572d-be0b-8ac7-596714208d41@microchip.com>
Date: Tue, 16 Jan 2018 10:24:59 +0200
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On 15.01.2018 22:27, Andy Shevchenko wrote:
> On Mon, Jan 15, 2018 at 10:41 AM, Claudiu Beznea
> <Claudiu.Beznea@microchip.com> 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
>