linux-kernel - Re: [PATCH v9 5/6] pwm: dwc: round rate divisions up

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Date:   Thu, 7 Sep 2023 23:36:35 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Ben Dooks <ben.dooks@...ethink.co.uk>
Cc:     linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Greentime Hu <greentime.hu@...ive.com>,
        jarkko.nikula@...ux.intel.com
Subject: Re: [PATCH v9 5/6] pwm: dwc: round rate divisions up

Hello,

[again dropped William Salmon and Jude Onyenegecha from Cc:]

On Thu, Sep 07, 2023 at 05:12:41PM +0100, Ben Dooks wrote:
> As suggested, round up the counter variables to ensure we
> always produce a longer period calculation.
> 
> Reported-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>
> ---
>  drivers/pwm/pwm-dwc-core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-dwc-core.c b/drivers/pwm/pwm-dwc-core.c
> index 3b856685029d..6358e3345210 100644
> --- a/drivers/pwm/pwm-dwc-core.c
> +++ b/drivers/pwm/pwm-dwc-core.c
> @@ -50,13 +50,13 @@ static int __dwc_pwm_configure_timer(struct dwc_pwm *dwc,
>  	 * 2^32 periods.
>  	 */
>  	tmp = state->duty_cycle * dwc->clk_rate;
> -	tmp = DIV_ROUND_CLOSEST_ULL(tmp, NSEC_PER_SEC);
> +	tmp = DIV_ROUND_UP_ULL(tmp, NSEC_PER_SEC);
>  	if (tmp < 1 || tmp > (1ULL << 32))
>  		return -ERANGE;
>  	low = tmp - 1;
>  
>  	tmp = (state->period - state->duty_cycle) * dwc->clk_rate;
> -	tmp = DIV_ROUND_CLOSEST_ULL(tmp, NSEC_PER_SEC);
> +	tmp = DIV_ROUND_UP_ULL(tmp, NSEC_PER_SEC);
>  	if (tmp < 1 || tmp > (1ULL << 32))
>  		return -ERANGE;
>  	high = tmp - 1;

Ah, I asked for that in the reply I just sent out to patch #4. Maybe move
this before the change from #4?! I think .get_state needs to be adapted
accoringly (to round up).

Best regards
Uwe

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

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