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@xxxxxx>
---
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
--
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