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于 2013年12月09日 19:55, Thierry Reding 写道:
> On Mon, Dec 09, 2013 at 07:04:12PM +0800, randy wrote: [...]
>> 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";
I added
samsung,pwm-outputs = <0>;
>> }; ================================ is it enough to make pwm
>> work, if the driver in kernel has been correct.
>
> It seems like you're missing the samsung,pwm-outputs property (see
> Documentation/devicetree/bindings/pwm/pwm-samsung.txt).
>
> Thierry
Well I have make it output to channel 0 now. But it doesn't work with
the config below. As it is a buzzer, I change your config.
=============================================
root@mifu:~# cat /sys/class/pwm/pwmchip0/pwm0/enable
1
root@mifu:~# cat /sys/class/pwm/pwmchip0/pwm0/period
1000000
root@mifu:~# cat /sys/class/pwm/pwmchip0/pwm0/duty_cycle
500000
==============================================
I have used a function generator with Vpp=2.2, it works.
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