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

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

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On Thu, Dec 12, 2013 at 10:27:04PM +0800, randy wrote:
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> 于 2013年12月12日 20:22, Thierry Reding 写道:
> > 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
> Yes, I am sure.
> > have the possibility to check the PWM output with a scope to see if
> > it outputs anything?
> I have used a oscillograph to capture, nothing(althought it show some
> waves, but it is nosie single captured by autoset). I have a scope but
> I don't think there is any different.
> > 
> > Thierry
> Ayaka
> Thank you

I don't know what else you could try, so I'm Cc'ing a couple of people
who have worked with this driver before, perhaps they can help resolve
this.

Thierry

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