Re: [PATCH v3] pwm: Device tree support for PWM polarity.

[Grant Likely <grant.likely@secretlab.ca>]

On Wed, 21 Nov 2012 13:10:44 +0530, "Philip, Avinash" <avinashphilip@ti.com> wrote:
> Add support for encoding PWM properties in bit encoded form with
> of_pwm_xlate_with_flags() function support. Platforms require platform
> specific PWM properties has to populate in 3rd cell of the pwm-specifier
> and PWM driver should also set .of_xlate support with this function.
> Currently PWM property polarity encoded in bit position 0 of the third
> cell in pwm-specifier.
> 
> Signed-off-by: Philip, Avinash <avinashphilip@ti.com>

Looks okay to me.

Acked-by: Grant Likely <grant.likely@secretlab.ca>

> ---
> Changes since v2:
> 	- Move PWM_SPEC_POLARITY to core.c
> 	- Remove dummy function
> 
> Changes since v1:
> 	- of_pwm_xlate_with_flags function support added.
> 	- Documentation update
> 
> :100644 100644 73ec962... 04b0dc4... M	Documentation/devicetree/bindings/pwm/pwm.txt
> :100644 100644 f5acdaa... 780cb6b... M	drivers/pwm/core.c
> :100644 100644 112b314... 6d661f3... M	include/linux/pwm.h
>  Documentation/devicetree/bindings/pwm/pwm.txt |   18 +++++++++++++--
>  drivers/pwm/core.c                            |   28 +++++++++++++++++++++++++
>  include/linux/pwm.h                           |    3 ++
>  3 files changed, 46 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt
> index 73ec962..04b0dc4 100644
> --- a/Documentation/devicetree/bindings/pwm/pwm.txt
> +++ b/Documentation/devicetree/bindings/pwm/pwm.txt
> @@ -37,10 +37,22 @@ device:
>  		pwm-names = "backlight";
>  	};
>  
> +Note that in the example above, specifying the "pwm-names" is redundant
> +because the name "backlight" would be used as fallback anyway.
> +
>  pwm-specifier typically encodes the chip-relative PWM number and the PWM
> -period in nanoseconds. Note that in the example above, specifying the
> -"pwm-names" is redundant because the name "backlight" would be used as
> -fallback anyway.
> +period in nanoseconds.
> +
> +Optionally, the pwm-specifier can encode a number of flags in a third cell:
> +- bit 0: PWM signal polarity (0: normal polarity, 1: inverse polarity)
> +
> +Example with optional PWM specifier for inverse polarity
> +
> +	bl: backlight {
> +		pwms = <&pwm 0 5000000 1>;
> +		pwm-names = "backlight";
> +	};
> +
>  
>  2) PWM controller nodes
>  -----------------------
> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> index f5acdaa..780cb6b 100644
> --- a/drivers/pwm/core.c
> +++ b/drivers/pwm/core.c
> @@ -32,6 +32,9 @@
>  
>  #define MAX_PWMS 1024
>  
> +/* flags in the third cell of the DT PWM specifier */
> +#define PWM_SPEC_POLARITY	(1 << 0)
> +
>  static DEFINE_MUTEX(pwm_lookup_lock);
>  static LIST_HEAD(pwm_lookup_list);
>  static DEFINE_MUTEX(pwm_lock);
> @@ -129,6 +132,31 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
>  	return 0;
>  }
>  
> +struct pwm_device *
> +of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
> +{
> +	struct pwm_device *pwm;
> +
> +	if (pc->of_pwm_n_cells < 3)
> +		return ERR_PTR(-EINVAL);
> +
> +	if (args->args[0] >= pc->npwm)
> +		return ERR_PTR(-EINVAL);
> +
> +	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
> +	if (IS_ERR(pwm))
> +		return pwm;
> +
> +	pwm_set_period(pwm, args->args[1]);
> +
> +	if (args->args[2] & PWM_SPEC_POLARITY)
> +		pwm_set_polarity(pwm, PWM_POLARITY_INVERSED);
> +	else
> +		pwm_set_polarity(pwm, PWM_POLARITY_NORMAL);
> +
> +	return pwm;
> +}
> +
>  static struct pwm_device *
>  of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
>  {
> diff --git a/include/linux/pwm.h b/include/linux/pwm.h
> index 112b314..6d661f3 100644
> --- a/include/linux/pwm.h
> +++ b/include/linux/pwm.h
> @@ -171,6 +171,9 @@ struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
>  					 unsigned int index,
>  					 const char *label);
>  
> +struct pwm_device *of_pwm_xlate_with_flags(struct pwm_chip *pc,
> +		const struct of_phandle_args *args);
> +
>  struct pwm_device *pwm_get(struct device *dev, const char *consumer);
>  void pwm_put(struct pwm_device *pwm);
>  
> -- 
> 1.7.0.4
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.