Re: [PATCH v2 1/4] pwm: rcar: Add support "atomic" API

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

Hello,

On Tue, Jan 08, 2019 at 12:28:11PM +0900, Yoshihiro Shimoda wrote:
> This patch adds support for "atomic" API. Behavior is the same as
> when using legacy APIs.
> 
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> ---
>  drivers/pwm/pwm-rcar.c | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
> index a41812f..ba70e83 100644
> --- a/drivers/pwm/pwm-rcar.c
> +++ b/drivers/pwm/pwm-rcar.c
> @@ -192,12 +192,49 @@ static void rcar_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
>  	rcar_pwm_update(rp, RCAR_PWMCR_EN0, 0, RCAR_PWMCR);
>  }
>  
> +static int rcar_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +			  struct pwm_state *state)
> +{
> +	struct rcar_pwm_chip *rp = to_rcar_pwm_chip(chip);
> +	struct pwm_state cur_state;
> +	int div, ret;
> +
> +	/* This HW doesn't support changing polarity */
> +	pwm_get_state(pwm, &cur_state);
> +	if (state->polarity != cur_state.polarity)
> +		return -ENOTSUPP;

Does the driver only support normal polarity or only inversed polarity?
If so checking against that would be more clear here.

> +
> +	div = rcar_pwm_get_clock_division(rp, state->period);
> +	if (div < 0)
> +		return div;
> +
> +	rcar_pwm_update(rp, RCAR_PWMCR_SYNC, RCAR_PWMCR_SYNC, RCAR_PWMCR);
> +
> +	ret = rcar_pwm_set_counter(rp, div, state->duty_cycle, state->period);
> +	if (!ret)
> +		rcar_pwm_set_clock_control(rp, div);
> +
> +	/* The SYNC should be set to 0 even if rcar_pwm_set_counter failed */
> +	rcar_pwm_update(rp, RCAR_PWMCR_SYNC, 0, RCAR_PWMCR);
> +
> +	if (!ret && state->enabled)
> +		ret = rcar_pwm_enable(chip, pwm);
> +
> +	if (!state->enabled) {
> +		rcar_pwm_disable(chip, pwm);
> +		ret = 0;
> +	}

Assume the PWM runs with duty cycle 33% when
pwm_apply_state({ .enabled=0, .duty_cycle=66, .period=100 }) is called.

Does this might result in a 66% wave form being emitted? If yes, this
needs fixing.

Best regards
Uwe

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