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? 2013?12?09? 16:52, Thierry Reding ??:
> 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.
>
I am sorry for I didn't notice that documents.
> Generally this should work somewhat like this:
>
> # echo 0 > /sys/class/pwm/pwmchip0/export
It seems can't work.
root@mifu:~# LANG=C echo 0 > /sys/class/pwm/pwmchip0/export
- -bash: echo: write error: Invalid argument
> # 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
Actually, I don't know whether the pwm works or not. In dmesg, I saw:
[ 853.690000] samsung-pwm 139d0000.pwm: tried to request PWM channel
0 without output
[ 876.930000] samsung-pwm 139d0000.pwm: tried to request PWM channel
0 without output
[ 879.615000] samsung-pwm 139d0000.pwm: tried to request PWM channel
1 without output
in my dts, I only add
================================
pwm@139D0000 {
status = "okay";
};
================================
is it enough to make pwm work, if the driver in kernel has been correct.
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