Hi Sean,
Am 30.01.24 um 10:08 schrieb Sean Young:
On Sun, Jan 28, 2024 at 05:36:30PM +0100, Stefan Wahren wrote:
From: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
Add a software PWM which toggles a GPIO from a high-resolution timer.
This will naturally not be as accurate or as efficient as a hardware
PWM, but it is useful in some cases. I have for example used it for
evaluating LED brightness handling (via leds-pwm) on a board where the
LED was just hooked up to a GPIO, and for a simple verification of the
timer frequency on another platform.
Since high-resolution timers are used, sleeping gpio chips are not
supported and are rejected in the probe function.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
Co-developed-by: Stefan Wahren <wahrenst@xxxxxxx>
Signed-off-by: Stefan Wahren <wahrenst@xxxxxxx>
---
...
+
+static int pwm_gpio_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+ const struct pwm_state *state)
+{
+ struct pwm_gpio *gpwm = container_of(chip, struct pwm_gpio, chip);
+ bool invert = state->polarity == PWM_POLARITY_INVERSED;
+ unsigned long flags;
Not sure this is necessary but how about:
if (state->duty_cycle < hrtimer_resolution ||
state->period - state->duty_cycle < hrtimer_resolution)
return -EINVAL;
i think i get the idea, but we need to care about corner cases like
duty_cycle = 0
