pwm: meson: Add support PWM_POLARITY_INVERSED when disabling (7341c785) · Commits · 戴 / test

meson_pwm_apply() has to consider the PWM polarity when disabling the output. With enabled=false and polarity=PWM_POLARITY_NORMAL the output needs to be LOW. The driver already supports this. With enabled=false and polarity=PWM_POLARITY_INVERSED the output needs to be HIGH. Implement this in the driver by internally enabling the output with the same settings that we already use for "period == duty". This fixes a PWM API violation which expects that the driver honors the polarity also for enabled=false. Due to the IP block not supporting this natively we only get "an as close as possible" to 100% HIGH signal (in my test setup with input clock of 24MHz and measuring the output with a logic analyzer at 24MHz sampling rate I got a duty cycle of 99.998475% on a Khadas VIM). Reviewed-by:

Neil Armstrong <narmstrong@baylibre.com> Signed-off-by:

Martin Blumenstingl <martin.blumenstingl@googlemail.com> Signed-off-by:

Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-meson.c

+22 −1

Original line number	Diff line number	Diff line
		@@ -245,6 +245,7 @@ static void meson_pwm_disable(struct meson_pwm meson, struct pwm_device pwm)
		static int meson_pwm_apply(struct pwm_chip chip, struct pwm_device pwm,
		struct pwm_state *state)
		{
		struct meson_pwm_channel *channel = pwm_get_chip_data(pwm);
		struct meson_pwm *meson = to_meson_pwm(chip);
		int err = 0;

		@@ -252,7 +253,27 @@ static int meson_pwm_apply(struct pwm_chip chip, struct pwm_device pwm,
		return -EINVAL;

		if (!state->enabled) {
		if (state->polarity == PWM_POLARITY_INVERSED) {
		/*
		* This IP block revision doesn't have an "always high"
		* setting which we can use for "inverted disabled".
		* Instead we achieve this using the same settings
		* that we use a pre_div of 0 (to get the shortest
		* possible duration for one "count") and
		* "period == duty_cycle". This results in a signal
		* which is LOW for one "count", while being HIGH for
		* the rest of the (so the signal is HIGH for slightly
		* less than 100% of the period, but this is the best
		* we can achieve).
		*/
		channel->pre_div = 0;
		channel->hi = ~0;
		channel->lo = 0;

		meson_pwm_enable(meson, pwm);
		} else {
		meson_pwm_disable(meson, pwm);
		}
		} else {
		err = meson_pwm_calc(meson, pwm, state);
		if (err < 0)

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