From: Arnd Bergmann <arnd@arndb.de>
To: Guru Das Srinagesh <gurus@codeaurora.org>
Cc: "Linux PWM List" <linux-pwm@vger.kernel.org>,
"Thierry Reding" <thierry.reding@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Subbaraman Narayanamurthy" <subbaram@codeaurora.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Shawn Guo" <shawnguo@kernel.org>,
"Sascha Hauer" <s.hauer@pengutronix.de>,
"Pengutronix Kernel Team" <kernel@pengutronix.de>,
"Fabio Estevam" <festevam@gmail.com>,
"NXP Linux Team" <linux-imx@nxp.com>
Subject: Re: [PATCH v11 06/12] pwm: imx27: Use 64-bit division macro and function
Date: Fri, 20 Mar 2020 18:09:39 +0100 [thread overview]
Message-ID: <CAK8P3a0qUMMMDmbp2FM-7D-U0Ys_zv0paYguFeyifafZurndEw@mail.gmail.com> (raw)
In-Reply-To: <5aae102e21c0e63ad2588ae1e174b48b06d25e96.1584667964.git.gurus@codeaurora.org>
On Fri, Mar 20, 2020 at 2:42 AM Guru Das Srinagesh <gurus@codeaurora.org> wrote:
> @@ -240,8 +240,7 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>
> period_cycles /= prescale;
> c = (unsigned long long)period_cycles * state->duty_cycle;
> - do_div(c, state->period);
> - duty_cycles = c;
> + duty_cycles = div64_u64(c, state->period);
>
This change looks fine, but I wonder if the code directly above it
c = clk_get_rate(imx->clk_per);
c *= state->period;
do_div(c, 1000000000);
period_cycles = c;
might run into an overflow when both the clock rate and the period
are large numbers.
Arnd
next prev parent reply other threads:[~2020-03-20 17:10 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 1:41 [PATCH v11 00/12] Convert PWM period and duty cycle to u64 Guru Das Srinagesh
2020-03-20 1:41 ` [Intel-gfx] " Guru Das Srinagesh
2020-03-20 1:41 ` Guru Das Srinagesh
2020-03-20 1:41 ` Guru Das Srinagesh
2020-03-20 1:41 ` [PATCH v11 01/12] drm/i915: Use 64-bit division macro Guru Das Srinagesh
2020-03-20 1:41 ` [Intel-gfx] " Guru Das Srinagesh
2020-03-20 1:41 ` Guru Das Srinagesh
2020-03-20 1:41 ` [PATCH v11 02/12] hwmon: pwm-fan: " Guru Das Srinagesh
2020-03-20 1:41 ` [PATCH v11 03/12] ir-rx51: " Guru Das Srinagesh
2020-03-20 1:41 ` [PATCH v11 04/12] pwm: clps711x: Cast period to u32 before use as divisor Guru Das Srinagesh
2020-03-20 17:11 ` Arnd Bergmann
2020-04-07 0:26 ` Guru Das Srinagesh
2020-03-20 1:41 ` [PATCH v11 05/12] pwm: pwm-imx-tpm: Use 64-bit division macro Guru Das Srinagesh
2020-03-20 1:41 ` [PATCH v11 06/12] pwm: imx27: Use 64-bit division macro and function Guru Das Srinagesh
2020-03-20 17:09 ` Arnd Bergmann [this message]
2020-03-30 20:43 ` Guru Das Srinagesh
2020-03-31 15:24 ` Arnd Bergmann
2020-03-31 20:20 ` Guru Das Srinagesh
2020-03-31 20:49 ` Thierry Reding
2020-04-02 20:16 ` Guru Das Srinagesh
2020-04-02 20:55 ` Guru Das Srinagesh
2020-04-02 21:16 ` Arnd Bergmann
2020-04-03 17:37 ` Guru Das Srinagesh
2020-04-03 19:13 ` Arnd Bergmann
2020-03-20 1:41 ` [PATCH v11 07/12] pwm: sifive: Use 64-bit division macro Guru Das Srinagesh
2020-03-20 1:41 ` Guru Das Srinagesh
2020-03-20 1:41 ` [PATCH v11 08/12] pwm: stm32-lp: Use %llu format specifier for period Guru Das Srinagesh
2020-03-20 10:45 ` Joe Perches
2020-03-30 19:30 ` Guru Das Srinagesh
2020-03-20 1:41 ` [PATCH v11 09/12] pwm: sun4i: Use 64-bit division function Guru Das Srinagesh
2020-03-20 17:02 ` Arnd Bergmann
2020-03-20 1:41 ` [PATCH v11 10/12] backlight: pwm_bl: " Guru Das Srinagesh
2020-03-20 1:41 ` Guru Das Srinagesh
2020-03-20 1:41 ` Guru Das Srinagesh
2020-03-20 13:31 ` Lee Jones
2020-03-20 13:31 ` Lee Jones
2020-03-20 13:31 ` Lee Jones
2020-03-24 11:07 ` Lee Jones
2020-03-24 11:07 ` Lee Jones
2020-03-24 11:07 ` Lee Jones
2020-03-24 12:57 ` Uwe Kleine-König
2020-03-24 12:57 ` Uwe Kleine-König
2020-03-24 12:57 ` Uwe Kleine-König
2020-03-24 13:04 ` Daniel Thompson
2020-03-24 13:04 ` Daniel Thompson
2020-03-24 13:04 ` Daniel Thompson
2020-03-24 14:24 ` Lee Jones
2020-03-24 14:24 ` Lee Jones
2020-03-24 14:24 ` Lee Jones
2020-03-24 14:43 ` Uwe Kleine-König
2020-03-24 14:43 ` Uwe Kleine-König
2020-03-24 14:43 ` Uwe Kleine-König
2020-04-15 9:26 ` Lee Jones
2020-04-15 9:26 ` Lee Jones
2020-04-15 9:26 ` Lee Jones
2020-03-20 1:41 ` [PATCH v11 11/12] clk: pwm: Assign u64 divisor to unsigned int before use Guru Das Srinagesh
2020-03-20 17:00 ` Arnd Bergmann
2020-03-20 18:42 ` David Laight
2020-04-07 2:40 ` Guru Das Srinagesh
2020-03-20 1:41 ` [PATCH v11 12/12] pwm: core: Convert period and duty cycle to u64 Guru Das Srinagesh
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