diff options
Diffstat (limited to 'include/linux/pwm.h')
| -rw-r--r-- | include/linux/pwm.h | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 150563a806d6..33f8decd9f38 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -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 |