diff options
| author | Philip, Avinash <avinashphilip@ti.com> | 2012-11-21 13:10:44 +0530 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@avionic-design.de> | 2012-11-22 22:47:12 +0100 |
| commit | 83af24027b3df1af5c5a9aa9adcdcfeb3429d3be (patch) | |
| tree | 3e104ed41554bb7e97378cc7cc3866c842306dff | |
| parent | 422470a8265fbb1d182c00ab2421f4b416ab2dba (diff) | |
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>
| -rw-r--r-- | Documentation/devicetree/bindings/pwm/pwm.txt | 17 | ||||
| -rw-r--r-- | drivers/pwm/core.c | 28 | ||||
| -rw-r--r-- | include/linux/pwm.h | 3 |
3 files changed, 45 insertions, 3 deletions
diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt index 73ec962bfe8..06e67247859 100644 --- a/Documentation/devicetree/bindings/pwm/pwm.txt +++ b/Documentation/devicetree/bindings/pwm/pwm.txt @@ -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 ----------------------- diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index f5acdaa5270..780cb6b8a8f 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 112b3143684..6d661f32e0e 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); |