Re: [PATCH] staging: greybus: introduce pwm_ops::apply

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Hello Uwe,

Thanks for the explain, now i can understand it better.

So, if redefining period and duty as u64 in gb_pwm_config_request is an acceptable solution, i will send patch v2.



在 2022/2/11 15:16, Uwe Kleine-König 写道:
Hello ,

On Fri, Feb 11, 2022 at 11:06:33AM +0800, Song Chen wrote:
在 2022/2/10 18:03, Uwe Kleine-König 写道:
On Thu, Feb 10, 2022 at 05:05:02PM +0800, Song Chen wrote:
Introduce apply in pwm_ops to replace legacy operations,
like enable, disable, config and set_polarity.

Signed-off-by: Song Chen <chensong_2000@xxxxxx>
   drivers/staging/greybus/pwm.c | 46 +++++++++++++++--------------------
   1 file changed, 19 insertions(+), 27 deletions(-)

diff --git a/drivers/staging/greybus/pwm.c b/drivers/staging/greybus/pwm.c
index 891a6a672378..e1889cf979b2 100644
--- a/drivers/staging/greybus/pwm.c
+++ b/drivers/staging/greybus/pwm.c
@@ -204,43 +204,35 @@ static void gb_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
   	gb_pwm_deactivate_operation(pwmc, pwm->hwpwm);
-static int gb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
-			 int duty_ns, int period_ns)
-	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
-	return gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_ns, period_ns);
-static int gb_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
-			       enum pwm_polarity polarity)
+static int gb_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			const struct pwm_state *state)
+	int ret;
   	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
-	return gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, polarity);
-static int gb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
-	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
+	/* set period and duty cycle*/
+	ret = gb_pwm_config_operation(pwmc, pwm->hwpwm, state->duty_cycle, state->period);

gb_pwm_config_operation's 3rd parameter is an u32, so you're loosing
bits here as state->duty_cycle is a u64. Ditto for period.

originally, pwm_apply_state --> pwm_apply_legacy --> gb_pwm_config -->
gb_pwm_config_operation is also loosing bits, does it mean greybus can live
with that?

This is true, I tried to address that, but Thierry had concerns.
was the patch I suggested.)

Or redefine gb_pwm_config_request, switch duty and period to __le64?

Don't use __le64, this is only for representing (little endian) register
values. u64 would be the right one.

Also it would be nice if you go from

	.duty_cycle = A, .period = B, .enabled = 1


	.duty_cycle = C, .period = D, .enabled = 0

that C/D wasn't visible on the output pin. So please disable earlier
(but keep enable at the end).

sorry, i don't quite understand this part,

To reexplain: If your hardware is configured for

	.duty_cycle = A, .period = B, .enabled = 1

and pwm_apply is called with

	.duty_cycle = C, .period = D, .enabled = 0

you configured the registers for .duty_cycle and .period first and only
then disable the PWM. This usually results in glitches because the
hardware shortly runs with

	.duty_cycle = C, .period = D, .enabled = 1

. So the idea is, to disable before configuring duty and period if the
eventual goal is a disabled state.

understood, thanks.

but is below code looking good to

static int gb_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
			const struct pwm_state *state)
	int err;
	bool enabled = pwm->state.enabled;
	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);

	/* set polarity */
	if (state->polarity != pwm->state.polarity) {
		if (enabled) {
			gb_pwm_disable_operation(pwmc, pwm->hwpwm);
			enabled = false;
		err = gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, state->polarity);
		if (err)
			return err;

	if (!state->enabled) {
		if (enabled)
			gb_pwm_disable_operation(pwmc, pwm->hwpwm);
		return 0;

	/* set period and duty cycle*/
	err = gb_pwm_config_operation(pwmc, pwm->hwpwm, state->duty_cycle, state->period);
	if (err)
		return err;

	/* enable/disable */
	if (!enabled)
		return gb_pwm_enable_operation(pwmc, pwm->hwpwm);

	return 0;

This looks good.

Best regards

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