[PATCH]dts: add bcm2835-pwm bindings

[PATCH]dts: add bcm2835-pwm bindings

[Bart Tanghe]

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?

Signed-off-by: Bart Tanghe <bart.tanghe@thomasmore.be>

diff --git a/arch/arm/boot/dts/bcm2835.dtsi b/arch/arm/boot/dts/bcm2835.dtsi
index 3342cb1..ba76bb4 100644
--- a/arch/arm/boot/dts/bcm2835.dtsi
+++ b/arch/arm/boot/dts/bcm2835.dtsi
@@ -146,6 +147,14 @@
 			interrupts = <1 9>;
 		};
 
+		pwm: pwm@7E20C000 {
+			compatible = "brcm,bcm2835-pwm";
+			reg = <0x7e20c000 0x28>;
+			clocks = <&clk_pwm>;
+			#pwm-cells = <2>;
+			status = "ok";
+		};
+
 		arm-pmu {
 			compatible = "arm,arm1176-pmu";
 		};
@@ -179,5 +188,13 @@
 			clock-output-names = "spi";
 			clock-frequency = <250000000>;
 		};
+
+		clk_pwm: pwm@3 {
+			compatible = "fixed-clock";
+			reg = <3>;
+			#clock-cells = <0>;
+			clock-output-names = "pwm";
+			clock-frequency = <9200000>;
+		};
 	};
 };

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

[Stephen Warren]

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.

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

[Bart Tanghe]

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

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

[Stephen Warren]

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?

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

[Bart Tanghe]

On 01/13/2015 05:19 PM, Stephen Warren wrote:
> 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?
Indeed, everything is described in the file. I thought about a specific pwm pinctrl section but it's the same for i2c and spi. This will just make the file unclear. 
No need to add documentation.

Regards,

Bart