linux-kernel - Re: [PATCH] staging: greybus: introduce pwm

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Message-ID: <20220210100342.q2t4ykgyymjzr3fj@pengutronix.de>
Date:   Thu, 10 Feb 2022 11:03:42 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Song Chen <chensong_2000@....cn>
Cc:     johan@...nel.org, elder@...nel.org, gregkh@...uxfoundation.org,
        thierry.reding@...il.com, lee.jones@...aro.org,
        greybus-dev@...ts.linaro.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH] staging: greybus: introduce pwm_ops::apply

On Thu, Feb 10, 2022 at 05:05:02PM +0800, Song Chen wrote:
> Introduce apply in pwm_ops to replace legacy operations,
> like enable, disable, config and set_polarity.
> 
> Signed-off-by: Song Chen <chensong_2000@....cn>
> ---
>  drivers/staging/greybus/pwm.c | 46 +++++++++++++++--------------------
>  1 file changed, 19 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/staging/greybus/pwm.c b/drivers/staging/greybus/pwm.c
> index 891a6a672378..e1889cf979b2 100644
> --- a/drivers/staging/greybus/pwm.c
> +++ b/drivers/staging/greybus/pwm.c
> @@ -204,43 +204,35 @@ static void gb_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
>  	gb_pwm_deactivate_operation(pwmc, pwm->hwpwm);
>  }
>  
> -static int gb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> -			 int duty_ns, int period_ns)
> -{
> -	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
> -
> -	return gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_ns, period_ns);
> -};
> -
> -static int gb_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
> -			       enum pwm_polarity polarity)
> +static int gb_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +			const struct pwm_state *state)
>  {
> +	int ret;
>  	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
>  
> -	return gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, polarity);
> -};
> -
> -static int gb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> -{
> -	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
> +	/* set period and duty cycle*/
> +	ret = gb_pwm_config_operation(pwmc, pwm->hwpwm, state->duty_cycle, state->period);

gb_pwm_config_operation's 3rd parameter is an u32, so you're loosing
bits here as state->duty_cycle is a u64. Ditto for period.

Also it would be nice if you go from

	.duty_cycle = A, .period = B, .enabled = 1

to

	.duty_cycle = C, .period = D, .enabled = 0

that C/D wasn't visible on the output pin. So please disable earlier
(but keep enable at the end).

Best regards
Uwe

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

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