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pwm: Add hardware readout infrastructure 

Add a ->get_state() function to the pwm_ops struct to let PWM drivers
initialize the PWM state attached to a PWM device.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Boris Brezillon 2016-04-14 21:17:40 +02:00 committed by Thierry Reding
parent 09a7e4a3d9
commit 15fa8a43c1
2 changed files with 31 additions and 0 deletions
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3
drivers/pwm/core.c
View File

@ -270,6 +270,9 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
pwm->hwpwm = i;
pwm->state.polarity = polarity;
if (chip->ops->get_state)
chip->ops->get_state(chip, pwm, &pwm->state);
radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
}

28
include/linux/pwm.h
View File

@ -206,6 +206,29 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
static inline void pwm_apply_args(struct pwm_device *pwm)
{
/*
* PWM users calling pwm_apply_args() expect to have a fresh config
* where the polarity and period are set according to pwm_args info.
* The problem is, polarity can only be changed when the PWM is
* disabled.
*
* PWM drivers supporting hardware readout may declare the PWM device
* as enabled, and prevent polarity setting, which changes from the
* existing behavior, where all PWM devices are declared as disabled
* at startup (even if they are actually enabled), thus authorizing
* polarity setting.
*
* Instead of setting ->enabled to false, we call pwm_disable()
* before pwm_set_polarity() to ensure that everything is configured
* as expected, and the PWM is really disabled when the user request
* it.
*
* Note that PWM users requiring a smooth handover between the
* bootloader and the kernel (like critical regulators controlled by
* PWM devices) will have to switch to the atomic API and avoid calling
* pwm_apply_args().
*/
pwm_disable(pwm);
pwm_set_polarity(pwm, pwm->args.polarity);
}
@ -217,6 +240,9 @@ static inline void pwm_apply_args(struct pwm_device *pwm)
* @set_polarity: configure the polarity of this PWM
* @enable: enable PWM output toggling
* @disable: disable PWM output toggling
* @get_state: get the current PWM state. This function is only
* called once per PWM device when the PWM chip is
* registered.
* @dbg_show: optional routine to show contents in debugfs
* @owner: helps prevent removal of modules exporting active PWMs
*/
@ -229,6 +255,8 @@ struct pwm_ops {
enum pwm_polarity polarity);
int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm);
void (*disable)(struct pwm_chip *chip, struct pwm_device *pwm);
void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state);
#ifdef CONFIG_DEBUG_FS
void (*dbg_show)(struct pwm_chip *chip, struct seq_file *s);
#endif