linux-kernel - Re: [PATCH]dts: add bcm2835-pwm bindings

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Date:	Tue, 13 Jan 2015 16:40:54 +0100
From:	Bart Tanghe <bart.tanghe@...masmore.be>
To:	Stephen Warren <swarren@...dotorg.org>, lee@...nel.org,
	devicetree@...r.kernel.org
CC:	thierry.reding@...il.com, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, linux@....linux.org.uk,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH]dts: add bcm2835-pwm bindings

On 01/10/2015 05:38 PM, Stephen Warren wrote:
> On 01/05/2015 08:33 AM, Bart Tanghe wrote:
>> To probe the bcm2835-pwm driver properly, this dts bindings has to be added 
>> to the bcm2835 dtsi file.
>> In expectation of a bcm2835 clock driver, I've added fixed-clock clock binding.
>> To change the status of the gpio pins into pwm output pins, some additional 
>> bindings has to be added but this has not to be done automatically.
>> Is it possible to document this bindings somewhere?
> 
> The pinctrl bindings allow you to do this. They're documented in:
> 
> Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
> Documentation/devicetree/bindings/pinctrl/brcm,bcm2835-gpio.txt
> 
> pinctrl setup would typically be added to the board file (i.e.
> arch/arm/boot/dts/bcm2835-rpi-b.dts) rather than the SoC file. I think
> on the RPi, the pins that can generate PWM aren't dedicated to PWM by
> the RPi board design (they could be GPIOs and probably other functions
> too) so we probably need to leave it up to individual users to add PWM
> configuration to their DT, if/when they use the PWM feature.
> 

Indeed, the pins aren't dedicated to pwm and can be used for other functions.
Is it usefull to add  the pwm pinctrl description to 
Documentation/devicetree/bindings/pinctrl/brcm,bcm2835-gpio.txt or is this 
useless? 

Regards,

Bart
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