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pwm: Add support referencing PWMs from ACPI

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In analogy to referencing a GPIO using the "gpios" property from ACPI,
support referencing a PWM using the "pwms" property.

ACPI entries must look like
 Package () {"pwms", Package ()
     { <PWM device reference>, <PWM index>, <PWM period> [, <PWM flags>]}}

In contrast to the DT implementation, only _one_ PWM entry in the "pwms"
property is supported. As a consequence "pwm-names"-property and
con_id lookup aren't supported.

Support for ACPI is added via the firmware-node framework which is an
abstraction layer on top of ACPI/DT. To keep this patch clean, DT and
ACPI paths are kept separate. The firmware-node framework could be used
to unify both paths in a future patch.

To support leds-pwm driver, an additional method devm_fwnode_pwm_get()
which supports both ACPI and DT configuration is exported.

Signed-off-by: Nikolaus Voss <nikolaus.voss@loewensteinmedical.de>
[thierry.reding@gmail.com: fix build failures for !ACPI]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Nikolaus Voss
2019-06-12 10:36:07 +02:00
committed by Thierry Reding
parent 4a5fa56cc0
commit 4a6ef8e37c
2 changed files with 132 additions and 0 deletions
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10
include/linux/pwm.h
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@@ -412,6 +412,9 @@ void pwm_put(struct pwm_device *pwm);
struct pwm_device *devm_pwm_get(struct device *dev, const char *con_id);
struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np,
const char *con_id);
struct pwm_device *devm_fwnode_pwm_get(struct device *dev,
struct fwnode_handle *fwnode,
const char *con_id);
void devm_pwm_put(struct device *dev, struct pwm_device *pwm);
#else
static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
@@ -518,6 +521,13 @@ static inline struct pwm_device *devm_of_pwm_get(struct device *dev,
return ERR_PTR(-ENODEV);
}
static inline struct pwm_device *
devm_fwnode_pwm_get(struct device *dev, struct fwnode_handle *fwnode,
const char *con_id)
{
return ERR_PTR(-ENODEV);
}
static inline void devm_pwm_put(struct device *dev, struct pwm_device *pwm)
{
}