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

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

[Tomasz Figa]

Hi Thierry, Ayaka,

On Saturday 14 of December 2013 13:44:09 Thierry Reding wrote:
> On Thu, Dec 12, 2013 at 10:27:04PM +0800, randy wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> > 
> > 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:
> > >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
> > >> 
> > >> 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.

I suspect invalid hardware configuration here.

Ayaka, could you post your board dts file with PWM enabled?

Btw. For topics related to Samsung's platforms, it's good to always CC
linux-samsung-soc ML.

Best regards,
Tomasz