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 09:06:37PM +0800, randy wrote:
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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.

Are you sure the function generator runs at the same frequency? Do you
have the possibility to check the PWM output with a scope to see if it
outputs anything?

Thierry

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