Re: [PATCH v3 5/5] gpio: mvebu: document zero pwm duty cycle limitation
From: Uwe Kleine-König <hidden>
Date: 2021-01-14 20:27:07
Also in:
linux-arm-kernel, linux-pwm
Hello Baruch, On Thu, Jan 14, 2021 at 08:57:37PM +0200, Baruch Siach wrote:
quoted hunk ↗ jump to hunk
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. + */
This is too easy. The right thing to do is to adapt .apply and .get_state to use this new information. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |
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