[PATCH 5/5] gpio: mvebu: document zero pwm duty cycle limitation

[Uwe Kleine-König]

On Mon, Jan 11, 2021 at 01:17:06PM +0200, Baruch Siach wrote:
> Add a comment on why the code never sets the 'on' register to zero.
> 
> Reported-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
> Signed-off-by: Baruch Siach <baruch at tkos.co.il>
> ---
>  drivers/gpio/gpio-mvebu.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
> index eb7456fa6d86..4261e3b22b4e 100644
> --- a/drivers/gpio/gpio-mvebu.c
> +++ b/drivers/gpio/gpio-mvebu.c
> @@ -706,6 +706,7 @@ static int mvebu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  	val = DIV_ROUND_UP_ULL(val, NSEC_PER_SEC);
>  	if (val > UINT_MAX)
>  		return -EINVAL;
> +	/* zero 'on' value does not work as expected for some reason */

What does the reference manual say about this? If there is no
information about this, please point this out, too. (Something like: The
reference manual is silent about this issue though.) Also I'd prefer to
read about the behaviour, so maybe mention that there is an occational
peek even when on is configured to 0. Does '$off = 0' has a symmetrical
issue?

Best regards
Uwe

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