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    Subject[PATCH v5 20/24] pwm: add the PWM initial state retrieval infra
    Date
    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>
    ---
    drivers/pwm/core.c | 3 +++
    include/linux/pwm.h | 28 ++++++++++++++++++++++++++++
    2 files changed, 31 insertions(+)

    diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
    index c2759bc..0e7f687 100644
    --- a/drivers/pwm/core.c
    +++ b/drivers/pwm/core.c
    @@ -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);
    }

    diff --git a/include/linux/pwm.h b/include/linux/pwm.h
    index 7bfeacf..73ca679 100644
    --- a/include/linux/pwm.h
    +++ b/include/linux/pwm.h
    @@ -205,6 +205,29 @@ 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);
    }

    @@ -216,6 +239,9 @@ 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
    */
    @@ -228,6 +254,8 @@ 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
    --
    2.5.0
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