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

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Message-ID: <54B54597.3010508@wwwdotorg.org>
Date:	Tue, 13 Jan 2015 09:19:35 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Bart Tanghe <bart.tanghe@...masmore.be>, 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 01/13/2015 08:40 AM, Bart Tanghe wrote:
> 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?

As far as I can tell, that file already describes everything required to 
configure those pins as PWM (or indeed any pins as any function). Can 
you expand on what you think is missing?
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