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Patch "pwm: omap-dmtimer: Round load and match values rather than truncate" has been added to the 4.5-stable tree

PATCH [email protected] 1 participant 1 message May 6, 2016

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This is a note to let you know that I've just added the patch titled

pwm: omap-dmtimer: Round load and match values rather than truncate

to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pwm-omap-dmtimer-round-load-and-match-values-rather-than-truncate.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 7b0883f33809ff0aeca9848193c31629a752bb77 Mon Sep 17 00:00:00 2001

From: David Rivshin <[email protected]>
Date: Fri, 29 Jan 2016 23:26:53 -0500
Subject: pwm: omap-dmtimer: Round load and match values rather than truncate

From: David Rivshin <[email protected]>

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

Patches currently in stable-queue which might be from [email protected] are

queue-4.5/pwm-omap-dmtimer-fix-inaccurate-period-and-duty-cycle-calculations.patch queue-4.5/pwm-omap-dmtimer-add-sanity-checking-for-load-and-match-values.patch queue-4.5/pwm-omap-dmtimer-round-load-and-match-values-rather-than-truncate.patch