diff options
| author | Liu Ying <Ying.liu@freescale.com> | 2013-01-30 12:31:55 +0800 |
|---|---|---|
| committer | Liu Ying <Ying.Liu@freescale.com> | 2013-01-31 10:16:14 +0800 |
| commit | 2a3185e5a0baef71e82acbfda420502b0073f2b0 (patch) | |
| tree | 202f07a013836a0c4385548f3bee93dd69284d36 | |
| parent | 7055ad7f4831ee99d5907bdba5e6757364c66c3d (diff) | |
ENGR00242214 IMX PWM:Correct duty cycle calculation
Since we've already reduced 2 cycles before writing PWMPR
register, the real period cycle on PWMO is the value of
period_cycles (before reducing 2). So, the following commit
message of ENGR00170342, which changes the duty cycle
calculation wrongly, is not reasonable:
===================================================
The chip document says the counter counts up to period_cycles + 1
and then is reset to 0, so the actual period of the PWM wave is
period_cycles + 2
===================================================
Revert "ENGR00170342 PWM: fix pwm output can't be set to 100% full duty"
This reverts commit ac3711f7f24b94db9f78fd7e9bf134c2ecd025ab.
Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
(cherry picked from commit b42be77aa7842834f0fb50924546701b668d7ab9)
| -rwxr-xr-x | arch/arm/plat-mxc/pwm.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/arch/arm/plat-mxc/pwm.c b/arch/arm/plat-mxc/pwm.c index b683d2eb6261..eb49057116f1 100755 --- a/arch/arm/plat-mxc/pwm.c +++ b/arch/arm/plat-mxc/pwm.c @@ -6,7 +6,7 @@ * published by the Free Software Foundation. * * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com> - * Copyright 2009-2012 Freescale Semiconductor, Inc. All Rights Reserved. + * Copyright 2009-2013 Freescale Semiconductor, Inc. All Rights Reserved. */ #include <linux/module.h> @@ -87,11 +87,7 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns) prescale = period_cycles / 0x10000 + 1; period_cycles /= prescale; - /* the chip document says the counter counts up to - * period_cycles + 1 and then is reset to 0, so the - * actual period of the PWM wave is period_cycles + 2 - */ - c = (unsigned long long)(period_cycles + 2) * duty_ns; + c = (unsigned long long)period_cycles * duty_ns; do_div(c, period_ns); duty_cycles = c; |