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    SubjectRe: [PATCH 3/4] pwm: pca9685: initialize all LED registers during probe
    On Wed, Feb 26, 2020 at 02:52:28PM +0100, Matthias Schiffer wrote:
    > Initialize all ON delays to 0 during probe, rather than doing it in
    > pca9685_pwm_enable.
    >
    > Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
    > ---
    > drivers/pwm/pwm-pca9685.c | 14 +++++++-------
    > 1 file changed, 7 insertions(+), 7 deletions(-)
    >
    > diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
    > index 393ab92aa945..370691b21107 100644
    > --- a/drivers/pwm/pwm-pca9685.c
    > +++ b/drivers/pwm/pwm-pca9685.c
    > @@ -289,13 +289,6 @@ static int pca9685_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
    > {
    > struct pca9685 *pca = to_pca(chip);
    >
    > - /*
    > - * The PWM subsystem does not support a pre-delay.
    > - * So, set the ON-timeout to 0
    > - */
    > - regmap_write(pca->regmap, LED_N_ON_L(pwm->hwpwm), 0);
    > - regmap_write(pca->regmap, LED_N_ON_H(pwm->hwpwm), 0);
    > -
    > /*
    > * Clear the full-off bit.
    > * It has precedence over the others and must be off.
    > @@ -388,6 +381,13 @@ static int pca9685_pwm_probe(struct i2c_client *client,
    > regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_L, 0);
    > regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, 0);
    >
    > + /*
    > + * The PWM subsystem does not support a pre-delay.
    > + * So, set the ON-timeout to 0
    > + */
    > + regmap_write(pca->regmap, PCA9685_ALL_LED_ON_H, 0);
    > + regmap_write(pca->regmap, PCA9685_ALL_LED_ON_L, 0);
    > +

    What is a pre-delay: Something like:
    _________ ______
    _____/ \_________________/
    ^ ^

    Where ^ marks the period start and then the time between period start
    and the rising signal is the pre-delay?

    If so, the IMHO more right approach is to keep the pre-delay until a new
    setting is applied and in .get_state ignore the pre-delay. This way you
    don't modify the output in .probe() which sounds right.

    Best regards
    Uwe

    --
    Pengutronix e.K. | Uwe Kleine-König |
    Industrial Linux Solutions | https://www.pengutronix.de/ |

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