Re: [beagleboard] Stretch pwm difference

2017-12-08 Thread Johan Henselmans 
OK, found out. Note to future self:

If you want /sys/clas/pwm/pwm-6:0, do an 
echo  0 > /sys/class/pwm/pwmchip6/export

I misunderstood that echo 0> /sys/class/pwm/pwmchip3/export was an unexport 
to reset things. 

To remove that channel, of course do a 
echo 0> /sys/class/pwm/pwmchip6/unexport
and
echo 1> /sys/class/pwm/pwmchip6/unexport

After that, first do some pwm settings, eg:
echo 500 > /sys/class/pwm/pwmchip6/pwm-6\:0/period
echo 500 > /sys/class/pwm/pwmchip6/pwm-6\:0/duty_cycle
echo 500 > /sys/class/pwm/pwmchip6/pwm-6\:1/period
echo 500 > /sys/class/pwm/pwmchip6/pwm-6\:1/duty_cycle

and after that you can do 

echo -n "1" > /sys/class/pwm/pwmchip6/pwm-6\:0/enable
echo -n "1" > /sys/class/pwm/pwmchip6/pwm-6\:1/enable

to have an effect. 

If you first enable the stuff before doing any setttings on period or 
duty_cycle, the kernel will not allow it.



On Thursday, December 7, 2017 at 10:35:08 AM UTC+1, Johan Henselmans wrote:
>
> I am trying to get p8_45 and p8_49 to run PWM2A and PWM2B signals. I am 
> running 4.14.3-ti-r14 with 
> enable_uboot_overlays=1
> enable_uboot_cape_universal=1
> disable_uboot_overlay_video=1
>
>
> According to the SRM that is possible, When I do an export to 
> echo 1 > /sys/class/pwm/pwmchip6/export
> , I only get /sys/clas/pwm/pwm-6:1
> With 
> echo 1 > /sys/class/pwm/pwmchip3/export
> , I get /sys/clas/pwm/pwm-3:0 and /sys/clas/pwm/pwm-3:1. 
>
> Why is that? Should I do anything else?
>
>
>
> On Friday, September 29, 2017 at 11:18:26 PM UTC+2, RobertCNelson wrote:
>>
>> On Fri, Sep 29, 2017 at 3:19 PM, William Hermans  
>> wrote: 
>> > Robert, 
>> > 
>> > Ok I think I see what you mean now( fully ). With universal IO and the 
>> > generic startup script enabled. I did see something similar to what you 
>> were 
>> > saying. However, if one disables both universal IO, and the generic 
>> startup 
>> > script, then writes their own custom overlay for all 3 of the PWM chips 
>> that 
>> > are dual channel. You get a structure like this: 
>> > 
>> > root@wgd:~# ls /sys/class/pwm/pwmchip*/ |grep pwm 
>> > /sys/class/pwm/pwmchip0/: 
>> > npwm 
>> > /sys/class/pwm/pwmchip2/: 
>> > npwm 
>> > /sys/class/pwm/pwmchip4/: 
>> > npwm 
>> > 
>> > This is consistent across multiple images on the same board. In this 
>> case a 
>> > 4G beaglebone black( rev C ). But at the same time as you can see from 
>> the 
>> > output above. The two PWM channels for each PWM chip are not enabled. 
>> In 
>> > Jessie, these are populated automatically at boot. How can I make that 
>> > happen in stretch ? I could write a script, but I think that is done 
>> > automatically through cape_manager in Jessie ? 
>>
>> What's happening in v4.4.x, the pwm's are now in the correct order, if 
>> you look at v4.4.x: (pwm came before ecap) 
>>
>> #4.4.88-ti-r129 
>> pwmchip0 -> 
>> ../../devices/platform/ocp/4830.epwmss/48300200.pwm/pwm/pwmchip0 
>> pwmchip2 -> 
>> ../../devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchip2 
>> pwmchip4 -> 
>> ../../devices/platform/ocp/48304000.epwmss/48304200.pwm/pwm/pwmchip4 
>> pwmchip6 -> 
>> ../../devices/platform/ocp/4830.epwmss/48300100.ecap/pwm/pwmchip6 
>> pwmchip7 -> 
>> ../../devices/platform/ocp/48304000.epwmss/48304100.ecap/pwm/pwmchip7 
>>
>> In v4.9.x: (since ecap are considered pwm's) they are now in the order 
>> of the register address: 
>>
>> pwmchip0 -> 
>> ../../devices/platform/ocp/4830.epwmss/48300100.ecap/pwm/pwmchip0 
>> pwmchip1 -> 
>> ../../devices/platform/ocp/4830.epwmss/48300200.pwm/pwm/pwmchip1 
>> pwmchip3 -> 
>> ../../devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchip3 
>> pwmchip5 -> 
>> ../../devices/platform/ocp/48304000.epwmss/48304100.ecap/pwm/pwmchip5 
>> pwmchip6 -> 
>> ../../devices/platform/ocp/48304000.epwmss/48304200.pwm/pwm/pwmchip6 
>>
>> In your case, you only want the dual mode "pwm", (48300200.pwm, 
>> 48302200.pwm, 48304200.pwm), you shouldn't blindly enable the 
>> "pwmchip0,2,4" as they are dynamic.  You should grep the symlink 
>> first. 
>>
>> Ps, watch out for v4.11.x too: 
>>
>> #v4.4.x/v4.9.x 
>> /sys/class/pwm/pwmchip1/: 
>> drwxr-xr-x 3 root root0 Sep 29 21:06 pwm0 
>> drwxr-xr-x 3 root root0 Sep 29 21:06 pwm1 
>>
>> #v4.11.x+ 
>>
>> /sys/class/pwm/pwmchip1/: 
>> drwxrwxr-x 3 root pwm 0 Sep 29 21:10 pwm-1:0 
>> drwxrwxr-x 3 root pwm 0 Sep 29 21:10 pwm-1:1 
>>
>> (ps, this last change is good thing, notice that udev correctly added 
>> the "root:pwm" rule.. ;) ) 
>>
>> Regards, 
>>
>> -- 
>> Robert Nelson 
>> https://rcn-ee.com/ 
>>
>

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Re: [beagleboard] Stretch pwm difference

2017-12-07 Thread Johan Henselmans 
I am trying to get p8_45 and p8_49 to run PWM2A and PWM2B signals. I am 
running 4.14.3-ti-r14 with 
enable_uboot_overlays=1
enable_uboot_cape_universal=1
disable_uboot_overlay_video=1


According to the SRM that is possible, When I do an export to 
echo 1 > /sys/class/pwm/pwmchip6/export
, I only get /sys/clas/pwm/pwm-6:1
With 
echo 1 > /sys/class/pwm/pwmchip3/export
, I get /sys/clas/pwm/pwm-3:0 and /sys/clas/pwm/pwm-3:1. 

Why is that? Should I do anything else?



On Friday, September 29, 2017 at 11:18:26 PM UTC+2, RobertCNelson wrote:
>
> On Fri, Sep 29, 2017 at 3:19 PM, William Hermans  > wrote: 
> > Robert, 
> > 
> > Ok I think I see what you mean now( fully ). With universal IO and the 
> > generic startup script enabled. I did see something similar to what you 
> were 
> > saying. However, if one disables both universal IO, and the generic 
> startup 
> > script, then writes their own custom overlay for all 3 of the PWM chips 
> that 
> > are dual channel. You get a structure like this: 
> > 
> > root@wgd:~# ls /sys/class/pwm/pwmchip*/ |grep pwm 
> > /sys/class/pwm/pwmchip0/: 
> > npwm 
> > /sys/class/pwm/pwmchip2/: 
> > npwm 
> > /sys/class/pwm/pwmchip4/: 
> > npwm 
> > 
> > This is consistent across multiple images on the same board. In this 
> case a 
> > 4G beaglebone black( rev C ). But at the same time as you can see from 
> the 
> > output above. The two PWM channels for each PWM chip are not enabled. In 
> > Jessie, these are populated automatically at boot. How can I make that 
> > happen in stretch ? I could write a script, but I think that is done 
> > automatically through cape_manager in Jessie ? 
>
> What's happening in v4.4.x, the pwm's are now in the correct order, if 
> you look at v4.4.x: (pwm came before ecap) 
>
> #4.4.88-ti-r129 
> pwmchip0 -> 
> ../../devices/platform/ocp/4830.epwmss/48300200.pwm/pwm/pwmchip0 
> pwmchip2 -> 
> ../../devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchip2 
> pwmchip4 -> 
> ../../devices/platform/ocp/48304000.epwmss/48304200.pwm/pwm/pwmchip4 
> pwmchip6 -> 
> ../../devices/platform/ocp/4830.epwmss/48300100.ecap/pwm/pwmchip6 
> pwmchip7 -> 
> ../../devices/platform/ocp/48304000.epwmss/48304100.ecap/pwm/pwmchip7 
>
> In v4.9.x: (since ecap are considered pwm's) they are now in the order 
> of the register address: 
>
> pwmchip0 -> 
> ../../devices/platform/ocp/4830.epwmss/48300100.ecap/pwm/pwmchip0 
> pwmchip1 -> 
> ../../devices/platform/ocp/4830.epwmss/48300200.pwm/pwm/pwmchip1 
> pwmchip3 -> 
> ../../devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchip3 
> pwmchip5 -> 
> ../../devices/platform/ocp/48304000.epwmss/48304100.ecap/pwm/pwmchip5 
> pwmchip6 -> 
> ../../devices/platform/ocp/48304000.epwmss/48304200.pwm/pwm/pwmchip6 
>
> In your case, you only want the dual mode "pwm", (48300200.pwm, 
> 48302200.pwm, 48304200.pwm), you shouldn't blindly enable the 
> "pwmchip0,2,4" as they are dynamic.  You should grep the symlink 
> first. 
>
> Ps, watch out for v4.11.x too: 
>
> #v4.4.x/v4.9.x 
> /sys/class/pwm/pwmchip1/: 
> drwxr-xr-x 3 root root0 Sep 29 21:06 pwm0 
> drwxr-xr-x 3 root root0 Sep 29 21:06 pwm1 
>
> #v4.11.x+ 
>
> /sys/class/pwm/pwmchip1/: 
> drwxrwxr-x 3 root pwm 0 Sep 29 21:10 pwm-1:0 
> drwxrwxr-x 3 root pwm 0 Sep 29 21:10 pwm-1:1 
>
> (ps, this last change is good thing, notice that udev correctly added 
> the "root:pwm" rule.. ;) ) 
>
> Regards, 
>
> -- 
> Robert Nelson 
> https://rcn-ee.com/ 
>

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Re: [beagleboard] Stretch pwm difference

2017-09-29 Thread William Hermans 
I think I have it figured out. If you  disable the ecap devices, the dual
channel populate normally. e.g. 0,2,4. But when you do have ecap enabled,
that's when things start to get squirrely. But at least it's not completely
random. There are or seem to be patterns when you have both ecap enabled.
My file structure looked exactly the same as your above where you had ecap
enabled.

On Fri, Sep 29, 2017 at 2:17 PM, Robert Nelson 
wrote:

> On Fri, Sep 29, 2017 at 3:19 PM, William Hermans 
> wrote:
> > Robert,
> >
> > Ok I think I see what you mean now( fully ). With universal IO and the
> > generic startup script enabled. I did see something similar to what you
> were
> > saying. However, if one disables both universal IO, and the generic
> startup
> > script, then writes their own custom overlay for all 3 of the PWM chips
> that
> > are dual channel. You get a structure like this:
> >
> > root@wgd:~# ls /sys/class/pwm/pwmchip*/ |grep pwm
> > /sys/class/pwm/pwmchip0/:
> > npwm
> > /sys/class/pwm/pwmchip2/:
> > npwm
> > /sys/class/pwm/pwmchip4/:
> > npwm
> >
> > This is consistent across multiple images on the same board. In this
> case a
> > 4G beaglebone black( rev C ). But at the same time as you can see from
> the
> > output above. The two PWM channels for each PWM chip are not enabled. In
> > Jessie, these are populated automatically at boot. How can I make that
> > happen in stretch ? I could write a script, but I think that is done
> > automatically through cape_manager in Jessie ?
>
> What's happening in v4.4.x, the pwm's are now in the correct order, if
> you look at v4.4.x: (pwm came before ecap)
>
> #4.4.88-ti-r129
> pwmchip0 -> ../../devices/platform/ocp/4830.epwmss/48300200.pwm/
> pwm/pwmchip0
> pwmchip2 -> ../../devices/platform/ocp/48302000.epwmss/48302200.pwm/
> pwm/pwmchip2
> pwmchip4 -> ../../devices/platform/ocp/48304000.epwmss/48304200.pwm/
> pwm/pwmchip4
> pwmchip6 -> ../../devices/platform/ocp/4830.epwmss/48300100.ecap/
> pwm/pwmchip6
> pwmchip7 -> ../../devices/platform/ocp/48304000.epwmss/48304100.ecap/
> pwm/pwmchip7
>
> In v4.9.x: (since ecap are considered pwm's) they are now in the order
> of the register address:
>
> pwmchip0 -> ../../devices/platform/ocp/4830.epwmss/48300100.ecap/
> pwm/pwmchip0
> pwmchip1 -> ../../devices/platform/ocp/4830.epwmss/48300200.pwm/
> pwm/pwmchip1
> pwmchip3 -> ../../devices/platform/ocp/48302000.epwmss/48302200.pwm/
> pwm/pwmchip3
> pwmchip5 -> ../../devices/platform/ocp/48304000.epwmss/48304100.ecap/
> pwm/pwmchip5
> pwmchip6 -> ../../devices/platform/ocp/48304000.epwmss/48304200.pwm/
> pwm/pwmchip6
>
> In your case, you only want the dual mode "pwm", (48300200.pwm,
> 48302200.pwm, 48304200.pwm), you shouldn't blindly enable the
> "pwmchip0,2,4" as they are dynamic.  You should grep the symlink
> first.
>
> Ps, watch out for v4.11.x too:
>
> #v4.4.x/v4.9.x
> /sys/class/pwm/pwmchip1/:
> drwxr-xr-x 3 root root0 Sep 29 21:06 pwm0
> drwxr-xr-x 3 root root0 Sep 29 21:06 pwm1
>
> #v4.11.x+
>
> /sys/class/pwm/pwmchip1/:
> drwxrwxr-x 3 root pwm 0 Sep 29 21:10 pwm-1:0
> drwxrwxr-x 3 root pwm 0 Sep 29 21:10 pwm-1:1
>
> (ps, this last change is good thing, notice that udev correctly added
> the "root:pwm" rule.. ;) )
>
> Regards,
>
> --
> Robert Nelson
> https://rcn-ee.com/
>

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Re: [beagleboard] Stretch pwm difference

2017-09-29 Thread Robert Nelson 
On Fri, Sep 29, 2017 at 3:19 PM, William Hermans  wrote:
> Robert,
>
> Ok I think I see what you mean now( fully ). With universal IO and the
> generic startup script enabled. I did see something similar to what you were
> saying. However, if one disables both universal IO, and the generic startup
> script, then writes their own custom overlay for all 3 of the PWM chips that
> are dual channel. You get a structure like this:
>
> root@wgd:~# ls /sys/class/pwm/pwmchip*/ |grep pwm
> /sys/class/pwm/pwmchip0/:
> npwm
> /sys/class/pwm/pwmchip2/:
> npwm
> /sys/class/pwm/pwmchip4/:
> npwm
>
> This is consistent across multiple images on the same board. In this case a
> 4G beaglebone black( rev C ). But at the same time as you can see from the
> output above. The two PWM channels for each PWM chip are not enabled. In
> Jessie, these are populated automatically at boot. How can I make that
> happen in stretch ? I could write a script, but I think that is done
> automatically through cape_manager in Jessie ?

What's happening in v4.4.x, the pwm's are now in the correct order, if
you look at v4.4.x: (pwm came before ecap)

#4.4.88-ti-r129
pwmchip0 -> ../../devices/platform/ocp/4830.epwmss/48300200.pwm/pwm/pwmchip0
pwmchip2 -> ../../devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchip2
pwmchip4 -> ../../devices/platform/ocp/48304000.epwmss/48304200.pwm/pwm/pwmchip4
pwmchip6 -> 
../../devices/platform/ocp/4830.epwmss/48300100.ecap/pwm/pwmchip6
pwmchip7 -> 
../../devices/platform/ocp/48304000.epwmss/48304100.ecap/pwm/pwmchip7

In v4.9.x: (since ecap are considered pwm's) they are now in the order
of the register address:

pwmchip0 -> 
../../devices/platform/ocp/4830.epwmss/48300100.ecap/pwm/pwmchip0
pwmchip1 -> ../../devices/platform/ocp/4830.epwmss/48300200.pwm/pwm/pwmchip1
pwmchip3 -> ../../devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchip3
pwmchip5 -> 
../../devices/platform/ocp/48304000.epwmss/48304100.ecap/pwm/pwmchip5
pwmchip6 -> ../../devices/platform/ocp/48304000.epwmss/48304200.pwm/pwm/pwmchip6

In your case, you only want the dual mode "pwm", (48300200.pwm,
48302200.pwm, 48304200.pwm), you shouldn't blindly enable the
"pwmchip0,2,4" as they are dynamic.  You should grep the symlink
first.

Ps, watch out for v4.11.x too:

#v4.4.x/v4.9.x
/sys/class/pwm/pwmchip1/:
drwxr-xr-x 3 root root0 Sep 29 21:06 pwm0
drwxr-xr-x 3 root root0 Sep 29 21:06 pwm1

#v4.11.x+

/sys/class/pwm/pwmchip1/:
drwxrwxr-x 3 root pwm 0 Sep 29 21:10 pwm-1:0
drwxrwxr-x 3 root pwm 0 Sep 29 21:10 pwm-1:1

(ps, this last change is good thing, notice that udev correctly added
the "root:pwm" rule.. ;) )

Regards,

-- 
Robert Nelson
https://rcn-ee.com/

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Re: [beagleboard] Stretch pwm difference

2017-09-29 Thread William Hermans 
I mean this hack fix is fairly trivial. Without the qep's being enabled.

debian@wgd:~$ sudo su
root@wgd:/home/debian# cd ~
root@wgd:~# nano pwm-enable.sh









*#!/bin/bashecho '0' > /sys/class/pwm/pwmchip0/exportecho '1' >
/sys/class/pwm/pwmchip0/exportecho '0' >
/sys/class/pwm/pwmchip2/exportecho '1' >
/sys/class/pwm/pwmchip2/exportecho '0' >
/sys/class/pwm/pwmchip4/exportecho '1' >
/sys/class/pwm/pwmchip4/exportexit 0*

root@wgd:~# chmod +x pwm-enable.sh
root@wgd:~# ./pwm-enable.sh

root@wgd:~# ls /sys/class/pwm/pwmchip*/ |grep pwm
/sys/class/pwm/pwmchip0/:
npwm
pwm0
pwm1
/sys/class/pwm/pwmchip2/:
npwm
pwm0
pwm1
/sys/class/pwm/pwmchip4/:
npwm
pwm0
pwm1

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Re: [beagleboard] Stretch pwm difference

2017-09-29 Thread William Hermans 
Robert,

Ok I think I see what you mean now( fully ). With universal IO and the
generic startup script enabled. I did see something similar to what you
were saying. However, if one disables both universal IO, and the generic
startup script, then writes their own custom overlay for all 3 of the PWM
chips that are dual channel. You get a structure like this:

root@wgd:~# ls /sys/class/pwm/pwmchip*/ |grep pwm
/sys/class/pwm/pwmchip0/:
npwm
/sys/class/pwm/pwmchip2/:
npwm
/sys/class/pwm/pwmchip4/:
npwm

This is consistent across multiple images on the same board. In this case a
4G beaglebone black( rev C ). But at the same time as you can see from the
output above. The two PWM channels for each PWM chip are not enabled. In
Jessie, these are populated automatically at boot. How can I make that
happen in stretch ? I could write a script, but I think that is done
automatically through cape_manager in Jessie ?

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Re: [beagleboard] Stretch pwm difference

2017-09-27 Thread William Hermans 
On Wed, Sep 27, 2017 at 1:31 PM, Robert Nelson 
wrote:

>
> Don't compare "pwmchipX's" directly, you need to dig into the symlink:
>
> root@beaglebone:/sys/class/pwm# ls -lh
> total 0
> lrwxrwxrwx 1 root root 0 Oct 13 17:14 pwmchip0 ->
> ../../devices/platform/ocp/4830.epwmss/48300200.pwm/pwm/pwmchip0
> lrwxrwxrwx 1 root root 0 Oct 13 17:14 pwmchip2 ->
> ../../devices/platform/ocp/4830.epwmss/48300100.ecap/pwm/pwmchip2
> lrwxrwxrwx 1 root root 0 Oct 13 17:14 pwmchip3 ->
> ../../devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchip3
> lrwxrwxrwx 1 root root 0 Oct 13 17:14 pwmchip5 ->
> ../../devices/platform/ocp/48304000.epwmss/48304200.pwm/pwm/pwmchip5
> lrwxrwxrwx 1 root root 0 Oct 13 17:14 pwmchip7 ->
> ../../devices/platform/ocp/48304000.epwmss/48304100.ecap/pwm/pwmchip7
>
> https://github.com/RobertCNelson/bb.org-overlays/
> blob/master/examples/cape-unversal-pwm.txt#L3-L9
>
> Regards,
>

So I get what you're saying, and get what the link is stating as well.
However, I'm not seeing how the pwmchipX value is changing at all. More to
the point, I really do not care if the underlying path changes, so long as
I do not have to completely rewrite a library in order to use the sysfs pwm
objects. Moreover, what good is loading a uboot overlay, if that overlay
does not do what it is supposed to do ?  It would be really nice to have
the pwm channels functioning before the OS is loaded.

*Jessie:*
root@wgd:~# ls -lh /sys/class/pwm
total 0
lrwxrwxrwx 1 root pwm 0 Sep 24 19:18 pwmchip0 ->
../../devices/platform/ocp/4830.epwmss/48300200.pwm/pwm/pwmchip0
lrwxrwxrwx 1 root pwm 0 Sep 24 19:18 pwmchip2 ->
../../devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchip2
lrwxrwxrwx 1 root pwm 0 Sep 24 19:18 pwmchip4 ->
../../devices/platform/ocp/48304000.epwmss/48304200.pwm/pwm/pwmchip4

*Stretch:*
root@wgd:~#  ls -lh /sys/class/pwm
total 0
lrwxrwxrwx 1 root pwm 0 Sep 26 21:20 pwmchip0 ->
../../devices/platform/ocp/4830.epwmss/48300200.pwm/pwm/pwmchip0
lrwxrwxrwx 1 root pwm 0 Sep 26 21:20 pwmchip2 ->
../../devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchip2
lrwxrwxrwx 1 root pwm 0 Sep 26 21:20 pwmchip4 ->
../../devices/platform/ocp/48304000.epwmss/48304200.pwm/pwm/pwmchip4

Seriously, I can run a script at boot, then run all the echo's I need in
order to populate the entire pwm subsystem for each "duel channel" pwm chip
I need to use. But it was my hope I did not have to.

With all of that said, this structure is all I care about.
root@wgd:~# uname -r
4.4.68-ti-r111
root@wgd:~# ls /sys/class/pwm/pwmchip*/ |grep pwm
/sys/class/pwm/pwmchip0/:
npwm
pwm0
pwm1
/sys/class/pwm/pwmchip2/:
npwm
pwm0
pwm1
/sys/class/pwm/pwmchip4/:
npwm
pwm0
pwm1

I would like Stretch to be the same at boot, without the need to run a
script if possible. But it's not.

root@wgd:~# uname -r
4.9.50-ti-r61
root@wgd:~# ls /sys/class/pwm/pwmchip*/ |grep pwm
/sys/class/pwm/pwmchip0/:
npwm
pwm0
/sys/class/pwm/pwmchip2/:
npwm
/sys/class/pwm/pwmchip4/:
npwm


Did I miss something in what you were saying ?

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[beagleboard] Stretch pwm difference

2017-09-27 Thread William Hermans 
So a few things to note about pwm behavior on the latest stretch image 
versus Jessie.
Obviously, Jessie by default runs an older kernel. 4.4.x versus 4.9.x.


First,

Jessie:
root@wgd:~# uname -r
4.4.68-ti-r111
root@wgd:~# lsmod |grep pwm
pwm_tiehrpwm 

Stretch:
root@wgd:~# uname -r
4.9.50-ti-r61
root@wgd:~# lsmod |grep pwm /* No output */

Here, I'm thinking the PWM module is built into the kernel. Because I'm 
running the same custom overlay on both boards, and both have a populated 
sysfs entry for pwm. However there is a difference.

Jessie:
root@wgd:~# ls /sys/class/pwm/pwmchip0
device  export  npwm  power  pwm0  pwm1  subsystem  uevent  unexport

Stretch:
root@wgd:~# ls /sys/class/pwm/pwmchip0
device  export  npwm  power  pwm0  subsystem  uevent  unexport

Here, initially, there was no pwm0 substructure. This populated after I ran 
echo '0' > /sys/class/pwm/pwmchip0/export as root. Further examination 
seems to indicate that pwm0 channel A is fully functional.

root@wgd:~# ls /sys/class/pwm/pwmchip0/pwm0/
capture  duty_cycle  enable  period  polarity  power  uevent

But I have not physically tested the hardware just yet.

So my questions are this. What's the difference ? Does this have something 
to do with the module being built into the kernel. or is there some kind of 
overlay change I'm not currrently aware of ?

config-pin for my project here is not an option . . . And in fact, 
cape_universal is disabled via the uboot envrorinment file.

Everything else seems to be exactly the same as far as I can tell, but I 
have not poured over the whole system just yet. Seems to be pretty stable 
too, but I've only been running the latest console stretch image for a few 
days now.


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