[PATCH v3 5/5] gpio: mvebu: document zero pwm duty cycle limitation
From: Baruch Siach <baruch@tkos.co.il>
Date: 2021-01-14 18:59:13
Also in:
linux-arm-kernel, linux-pwm
Subsystem:
gpio subsystem, the rest · Maintainers:
Linus Walleij, Bartosz Golaszewski, Linus Torvalds
Add a comment on why the code never sets on/off registers to zero. Reported-by: Uwe Kleine-König <redacted> Analyzed-by: Russell King [off-list ref] Signed-off-by: Baruch Siach <baruch@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