Commit 83af2402 authored by Philip, Avinash's avatar Philip, Avinash Committed by Thierry Reding
Browse files

pwm: Device tree support for PWM polarity 



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: default avatarPhilip, Avinash <avinashphilip@ti.com>
Acked-by: default avatarGrant Likely <grant.likely@secretlab.ca>
Signed-off-by: default avatarThierry Reding <thierry.reding@avionic-design.de>
parent 422470a8

Documentation/devicetree/bindings/pwm/pwm.txt

+14 −3
Original line number Diff line number Diff line
@@ -37,10 +37,21 @@ 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

-----------------------

drivers/pwm/core.c

+28 −0
Original line number Diff line number Diff line
@@ -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)

{

include/linux/pwm.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

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