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drivers: pwm_nrfx: Fix handling of zero length periods

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When the driver was called to set the period length for a channel
to 0, it set the COUNTERTOP register in the PWM peripheral to 0,
what resulted in an undefined behavior of the peripheral (and lack
of the STOPPED event sometimes).
The PWM API does not precise how should a zero length period be
handled; some drivers return the -EINVAL error in such case, some
do not. This patch fixes the pwm_nrfx driver so that it does not
change the previously used COUNTERTOP register value when the period
length is set to 0, and because the pulse cycles are always limited
by the driver to period cycles (so 0 in this case), in result the
relevant channel is simply deactivated. This allows users to switch
off a channel by requesting the pulse width to be set to 0 without
providing a non-zero period in such call.

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>
This commit is contained in:
Andrzej Głąbek 2021-10-07 12:05:04 +02:00 • committed by Carles Cufí
commit 165c14dc60
1 changed files with 5 additions and 2 deletions
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7
drivers/pwm/pwm_nrfx.c
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@ -169,10 +169,13 @@ static int pwm_nrfx_pin_set(const struct device *dev, uint32_t pwm,
pulse_cycles /= 2;
}
/* Check if period_cycle is either matching currently used, or
/* Check if period_cycles is either matching currently used, or
* possible to use with our prescaler options.
* Don't do anything if the period length happens to be zero.
* In such case, pulse cycles will be right below limited to 0
* and this will result in making the channel inactive.
*/
if (period_cycles != data->period_cycles) {
if (period_cycles != 0 && period_cycles != data->period_cycles) {
int ret = pwm_period_check_and_set(config, data, channel,
period_cycles);
if (ret) {