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

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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: 6604c6556d ("pwm: Add PWM driver for OMAP using dual-mode timers")
Signed-off-by: David Rivshin <drivshin@allworx.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
David Rivshin 2016-01-29 23:26:53 -05:00 committed by Thierry Reding
parent cd37888142
commit 7b0883f338
1 changed files with 1 additions and 5 deletions
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6
drivers/pwm/pwm-omap-dmtimer.c
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@ -49,11 +49,7 @@ to_pwm_omap_dmtimer_chip(struct pwm_chip *chip)
static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns) static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns)
{ {
u64 c = (u64)clk_rate * ns; return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC);
do_div(c, NSEC_PER_SEC);
return c;
} }
static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap) static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)