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| author | Vladimir Zapolskiy <vz@mleia.com> | 2015-12-06 13:32:02 +0200 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2015-12-16 17:01:06 +0100 |
| commit | d6dbdf0ddefa581e49c2abe5fb0eb17d14111d89 (patch) | |
| tree | 49d6a3c2c8119480c873eb8f2cf7da9d16a2f2a5 /drivers/pwm | |
| parent | 5a9fc9c666d5d759699cf5495bda85f1da0d747e (diff) | |
| download | linux-d6dbdf0ddefa581e49c2abe5fb0eb17d14111d89.tar.gz | |
pwm: lpc32xx: return ERANGE, if requested period is not supported
Instead of silent acceptance of unsupported requested configuration for PWM period and setting the boundary supported value, return -ERANGE to a caller. Duty period value equal to 0 or period is still accepted to allow configuration by PWM sysfs interface, when it is set to 0 by default. For reference this is a list of restrictions on period_ns == 1/freq: | PWM parent clock | parent clock divisor | max freq | min freq | +------------------+----------------------+----------+----------+ | HCLK == 13 MHz | 1 (min) | 50.7 KHz | 198.3 Hz | | HCLK == 13 MHz | 15 (max) | 3.38 KHz | 13.22 Hz | | RTC == 32.7 KHz | 1 (min) | 128 Hz | 0.5 Hz | | RTC == 32.7 KHz | 15 (max) | 8.533 Hz | 0.033 Hz | Note that PWM sysfs interface does not support setting of period more than NSEC_PER_SEC / MAX_INT32 ~ 2 seconds, however this PWM controller supports a period up to 30 seconds. Signed-off-by: Vladimir Zapolskiy <vz@mleia.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'drivers/pwm')
| -rw-r--r-- | drivers/pwm/pwm-lpc32xx.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/pwm/pwm-lpc32xx.c b/drivers/pwm/pwm-lpc32xx.c index 294a68f82558..4d470c1a406a 100644 --- a/drivers/pwm/pwm-lpc32xx.c +++ b/drivers/pwm/pwm-lpc32xx.c @@ -41,9 +41,9 @@ static int lpc32xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, /* The highest acceptable divisor is 256, which is represented by 0 */ period_cycles = div64_u64(c * period_ns, (unsigned long long)NSEC_PER_SEC * 256); - if (!period_cycles) - period_cycles = 1; - if (period_cycles > 255) + if (!period_cycles || period_cycles > 256) + return -ERANGE; + if (period_cycles == 256) period_cycles = 0; /* Compute 256 x #duty/period value and care for corner cases */ |