[PATCH v3 5/5] gpio: mvebu: document zero pwm duty cycle limitation

[Baruch Siach]

Add a comment on why the code never sets on/off registers to zero.

Reported-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
Analyzed-by: Russell King <linux at armlinux.org.uk>
Signed-off-by: Baruch Siach <baruch at tkos.co.il>
---
 drivers/gpio/gpio-mvebu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
index 6b017854ce61..09780944bef9 100644
--- a/drivers/gpio/gpio-mvebu.c
+++ b/drivers/gpio/gpio-mvebu.c
@@ -706,6 +706,10 @@ static int mvebu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	do_div(val, NSEC_PER_SEC);
 	if (val > UINT_MAX)
 		return -EINVAL;
+	/*
+	 * Zero on/off values don't work as expected. Experimentation shows
+	 * that zero value is treated as 2^32. This behavior is not documented.
+	 */
 	if (val)
 		on = val;
 	else
-- 
2.29.2