linux-kernel - [PATCH 4.5 30/88] pwm: omap-dmtimer: Round load and match values rather than truncate

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Message-Id: <20160509071953.622122982@linuxfoundation.org>
Date:	Mon,  9 May 2016 09:21:19 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, David Rivshin <drivshin@...worx.com>,
	Neil Armstrong <narmstrong@...libre.com>,
	Thierry Reding <thierry.reding@...il.com>
Subject: [PATCH 4.5 30/88] pwm: omap-dmtimer: Round load and match values rather than truncate

4.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Rivshin <drivshin@...worx.com>

commit 7b0883f33809ff0aeca9848193c31629a752bb77 upstream.

When converting period and duty_cycle from nanoseconds to fclk cycles,
the error introduced by the integer division can be appreciable, especially
in the case of slow fclk or short period. Use DIV_ROUND_CLOSEST_ULL() so
that the error is kept to +/- 0.5 clock cycles.

Fixes: 6604c6556db9 ("pwm: Add PWM driver for OMAP using dual-mode timers")
Signed-off-by: David Rivshin <drivshin@...worx.com>
Acked-by: Neil Armstrong <narmstrong@...libre.com>
Signed-off-by: Thierry Reding <thierry.reding@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/pwm/pwm-omap-dmtimer.c |    6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

--- a/drivers/pwm/pwm-omap-dmtimer.c
+++ b/drivers/pwm/pwm-omap-dmtimer.c
@@ -49,11 +49,7 @@ to_pwm_omap_dmtimer_chip(struct pwm_chip
 
 static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns)
 {
-	u64 c = (u64)clk_rate * ns;
-
-	do_div(c, NSEC_PER_SEC);
-
-	return c;
+	return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC);
 }
 
 static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)