From: Guru Das Srinagesh <gurus@codeaurora.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "Linux PWM List" <linux-pwm@vger.kernel.org>,
"Thierry Reding" <thierry.reding@gmail.com>,
"Uwe Kleine-König" <uwe@kleine-koenig.org>,
"Subbaraman Narayanamurthy" <subbaram@codeaurora.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Alexander Shiyan" <shc_work@mail.ru>
Subject: Re: [PATCH v9 04/11] pwm: clps711x: Use 64-bit division macro
Date: Tue, 17 Mar 2020 16:30:05 -0700 [thread overview]
Message-ID: <20200317233003.GA11350@codeaurora.org> (raw)
In-Reply-To: <CAK8P3a2Hi_AoRC3g7qKth4e_Y1jZrbBDhWUb3YPZm10FWMu-ig@mail.gmail.com>
On Tue, Mar 17, 2020 at 11:22:06PM +0100, Arnd Bergmann wrote:
> > diff --git a/drivers/pwm/pwm-clps711x.c b/drivers/pwm/pwm-clps711x.c
> > index 924d39a..ba9500a 100644
> > --- a/drivers/pwm/pwm-clps711x.c
> > +++ b/drivers/pwm/pwm-clps711x.c
> > @@ -43,7 +43,7 @@ static void clps711x_pwm_update_val(struct clps711x_chip *priv, u32 n, u32 v)
> > static unsigned int clps711x_get_duty(struct pwm_device *pwm, unsigned int v)
> > {
> > /* Duty cycle 0..15 max */
> > - return DIV_ROUND_CLOSEST(v * 0xf, pwm->args.period);
> > + return DIV64_U64_ROUND_CLOSEST(v * 0xf, pwm->args.period);
> > }
>
> Is it actually going to exceed U32_MAX? If not, a type cast may be
> more appropriate here than the expensive 64-bit division.
With the final change in this patch series, the framework will support
periods that exceed U32_MAX. My concern is that using a typecast would
mean that in those cases, this driver will not support > U32_MAX values.
Using DIV64_U64_ROUND_CLOSEST makes the driver future proof and able to
handle > U32_MAX values correctly. What do you think?
Thank you.
Guru Das.
next prev parent reply other threads:[~2020-03-17 23:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1584473399.git.gurus@codeaurora.org>
2020-03-17 20:05 ` [PATCH v9 01/11] drm/i915: Use 64-bit division macro Guru Das Srinagesh
2020-03-18 19:08 ` Jani Nikula
2020-03-19 19:35 ` Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 02/11] hwmon: pwm-fan: " Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 03/11] ir-rx51: " Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 04/11] pwm: clps711x: " Guru Das Srinagesh
2020-03-17 22:22 ` Arnd Bergmann
2020-03-17 23:30 ` Guru Das Srinagesh [this message]
2020-03-18 9:49 ` Arnd Bergmann
2020-03-18 17:00 ` Guru Das Srinagesh
2020-03-18 19:38 ` Arnd Bergmann
2020-03-19 20:51 ` Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 05/11] pwm: pwm-imx-tpm: " Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 06/11] pwm: imx27: Use 64-bit division macro and function Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 07/11] pwm: sifive: Use 64-bit division macro Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 08/11] pwm: stm32-lp: Use %llu format specifier for period Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 09/11] pwm: sun4i: Use 64-bit division function Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 10/11] backlight: pwm_bl: " Guru Das Srinagesh
2020-03-17 20:05 ` [PATCH v9 11/11] pwm: core: Convert period and duty cycle to u64 Guru Das Srinagesh
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