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

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

[randy]

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

[Thierry Reding]

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On Mon, Dec 09, 2013 at 01:22:02AM +0800, randy wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> 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.

Generally this should work somewhat like this:

	# echo 0 > /sys/class/pwm/pwmchip0/export
	# 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

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

[randy]

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? 2013?12?09? 16:52, Thierry Reding ??:
> On Mon, Dec 09, 2013 at 01:22:02AM +0800, randy wrote:
>> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
>> 
>> 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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Re: [exynos4412]How to test a pwm device, is there a test program?

[Thierry Reding]

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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";
> };
> ================================
> 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

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

[randy]

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

[Thierry Reding]

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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
have the possibility to check the PWM output with a scope to see if it
outputs anything?

Thierry

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

[randy]

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

[Thierry Reding]

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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.

Thierry

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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