Re: [v9 2/2] pwm: Add Aspeed ast2600 PWM support

Hello Billy,

On Fri, Jul 16, 2021 at 01:48:20AM +0000, Billy Tsai wrote:

On 2021/7/15, 11:06 PM, "Uwe Kleine-König" [off-list ref]> wrote:
    > Another is: The PWM doesn't support duty_cycle 0, on such a request the
    > PWM is disabled which results in a constant inactive level.

    > (This is correct, is it? Or does it yield a constant 0 level?)

Our pwm can support duty_cycle 0 by unset CLK_ENABLE.

This has a slightly different semantic though. Some consumer might
expect that the following sequence:

	pwm_apply(mypwm, { .period = 10000, .duty_cycle = 10000, .enabled = true })
	pwm_apply(mypwm, { .period = 10000, .duty_cycle = 0, .enabled = true })
	pwm_apply(mypwm, { .period = 10000, .duty_cycle = 10000, .enabled = true })

results in the output being low for an integer multiple of 10 µs. This
isn't given with setting CLK_ENABLE to zero, is it? (I didn't recheck,
if the PWM doesn't complete periods on reconfiguration this doesn't
matter much though.)

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
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