Re: [exynos4412]How to test a pwm device, is there a test program?

[Thierry Reding <thierry.reding@gmail.com>]

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On Mon, Dec 09, 2013 at 01:22:02AM +0800, randy wrote:
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> The dts for my board tiny4412 is ready, in my board, the pwm 0 is
> connect to a buzzer. I want to test whether it works, but I don't know
> any test util. As I have a oscillograph, there is no problem for me to
> measure whether the output is correct.
> Thanks

You can use the sysfs interface to easily test the PWM functionality.
The documentation for that is in Documentation/pwm.txt and
Documentation/ABI/testing/sysfs-class-pwm.

Generally this should work somewhat like this:

	# echo 0 > /sys/class/pwm/pwmchip0/export
	# echo 50000 > /sys/class/pwm/pwmchip0/pwm0/period
	# echo 25000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle
	# echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable

Which should configure PWM 0 to run at a period of 50000 ns and a 50%
duty-cycle.

	# echo 0 > /sys/class/pwm/pwmchip0/pwm0/disable

Stops the PWM signal and when you're done with all the testing you can
export the PWM (so that it can be reused):

	# echo 0 > /sys/class/pwm/pwmchip0/unexport

Thierry

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