linux-kernel - Re: [PATCH v9 4/6] pwm: dwc: use clock rate in hz to avoid rounding issues

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Message-ID: <20230911194751.mohdwipo74ccgail@pengutronix.de>
Date:   Mon, 11 Sep 2023 21:47:51 +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 4/6] pwm: dwc: use clock rate in hz to avoid rounding
 issues

Hello Ben,

On Mon, Sep 11, 2023 at 08:33:02AM +0100, Ben Dooks wrote:
> On 07/09/2023 22:34, Uwe Kleine-König wrote:
> > > +	duty *= NSEC_PER_SEC;
> > > +	period *= NSEC_PER_SEC;
> > 
> > A comment that/why this cannot overflow would be nice. (I didn't check,
> > maybe it can?)
> 
> I /think/ that as long as NSEC_PER_SEC  2^32 then this shouldn't
> overflow.

I guess NSEC_PER_SEC won't change in the near future :-)

double checking and writing the result down in a comment would be
appreciated.

Best regards
Uwe

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

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