dect
/
linux-2.6
Archived
13
0
Fork 0
Code Releases Activity

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: Philip, Avinash <avinashphilip@ti.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
This commit is contained in:
Philip, Avinash 2012-11-21 13:10:44 +05:30 committed by Thierry Reding
parent 422470a826
commit 83af24027b
3 changed files with 45 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
Documentation/devicetree/bindings/pwm/pwm.txt
View File

@ -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
-----------------------

28
drivers/pwm/core.c
View File

@ -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)
{

3
include/linux/pwm.h
View File

@ -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);