Add eQEP support for 4.x kernel

[theonteg]

Hello,
Is is possible to add support to read position and change period of eQEP in kernel 4.x ?

[pdp7]

@theonteg I believe this should be a matter of writing to files in /sys. Do you know that paths for position and periond?

[theonteg]

@pdp7 yes,
for eQEP0: /sys/devices/platform/ocp/48300000.epwmss/48300180.eqep/
for eQEP1: /sys/devices/platform/ocp/48302000.epwmss/48302180.eqep/
for eQEP2: /sys/devices/platform/ocp/48304000.epwmss/48304180.eqep/
The files enabled, period and position.

This is available in latest 4.4 (4.4.31-ti-r67) and 4.1 kernels. Some previous versions doesn't have these files.

[pdp7]

@theonteg Thanks for the details. I see that @rseetham added RotaryEncoder to PyBBIO.

It looks like it should be possible to add something similar to Adafruit_BBIO. I can't give an estimate as to when I will have time to implement this feature, but I'd welcome any pull requests.

[pdp7]

FYI - I came across this code today by @mvduin and wanted to make a note in case it useful for implementation here:
py-uio/ti/qep.py

add preliminary QEP code

[mvduin]

Note that it doesn't use the (very limited, non-mainline) kernel driver but directly accesses the peripheral. This means that apart from DT differences it should work on any kernel (the uio_pdrv_genirq driver has existed since ancient times, and is enabled on rcn's kernels all the way down to 3.8-series if you use a not-too-ancient build).

[pdp7]

@theonteg Here's an update:

I found a bug in the tieqep driver in the 4.9 kernel (which is currently in testing for the beaglebone debian image). I've tracked down the solution and Robert C. Nelson, who builds the beaglebone kernels and debian images, has now merged the fix:

tieqep: add patch to fix unhandled fault on 4.9 kernel
RobertCNelson/ti-linux-kernel-dev@f89418b

I can now read the eQEP position OK on these kernels via /sys with these kernels:

• 4.1.30-ti-r70
• 4.4.44-ti-r85
• 4.9.6-ti-r18

This issue #122 is the only open issue for this repo, so I am now going to start developing eQEP support for Adafruit_BBIO.

[RobertCNelson]

4.4.45-ti-r86/4.4.45-ti-rt-r86 with @pdp7 's fix should hit the apt repo later this afternoon.

Edit: meant: 4.9.7-ti-r19/4.9.7-ti-rt-r19

Regards,

[pdp7]

@RobertCNelson Will there also be a package for the new 4.9.7-ti-r19 kernel?

[RobertCNelson]

@pdp7 crap, sorry meant: 4.9.7-ti-r19/4.9.7-ti-rt-r19, complete brainfart..

Regards,

[pdp7]

I'm using P8.11 and P8.12 for testing a rotary encoder.

Using cape-universal:

debian@beaglebone:~$ cat /sys/devices/platform/bone_capemgr/slots
 0: PF----  -1 
 1: PF----  -1 
 2: PF----  -1 
 3: PF----  -1 
 4: P-O-L-   0 Override Board Name,00A0,Override Manuf,univ-all
 5: P-O-L-   1 Override Board Name,00A0,Override Manuf,BB-ADC

/boot/uEnv.txt:

uname_r=4.4.47-ti-r87
dtb=am335x-boneblack-overlay.dtb
cmdline=coherent_pool=1M quiet cape_universal=enable

Configure the pin mode for eQEP:

debian@beaglebone:~$ config-pin p8.11 qep && config-pin p8.12 qep

debian@beaglebone:~$ config-pin -q p8.11 && config-pin -q p8.12 
P8_11 Mode: qep
P8_12 Mode: qep

System info:

debian@beaglebone:~$ uname -a
Linux beaglebone 4.4.47-ti-r87 #1 SMP Mon Feb 6 22:21:49 UTC 2017 armv7l GNU/Linux
debian@beaglebone:~$ cat /etc/debian_version 
8.7
debian@beaglebone:~$ sudo cat /etc/dogtag 
BeagleBoard.org Debian Image 2015-12-07

Check the position:

debian@beaglebone:~$ find /sys/devices |grep eqep |grep position$
/sys/devices/platform/ocp/48302000.epwmss/48302180.eqep/position
/sys/devices/platform/ocp/48304000.epwmss/48304180.eqep/position
/sys/devices/platform/ocp/48300000.epwmss/48300180.eqep/position
debian@beaglebone:~$ cat `find /sys/devices |grep eqep |grep position$`
0
-3251
0
debian@beaglebone:~$ watch -n 1 cat /sys/devices/platform/ocp/48304000.epwmss/48304180.eqep/position

For P8.11 and P8.12:

/sys/devices/platform/ocp/48304000.epwmss/48304180.eqep/position

[pdp7]

NOTE: my BBB is running Debian 8.8 with Linux 4.4.62-ti-r99 kernel

I've now been able to use eqep0, eqep1 and eqep2 OK with config-pin. I had to modify cape-universala-00A0.dts to enable pins P8_33 and P8_35 for eqep1: pdp7/bb.org-overlays@fd65f9e

Enable eqep0 for pins P9_27 and P9_92 (an alias for P9_42.1):

config-pin P9.27 qep
config-pin P9.92 qep 

Enable eqep1 for pins P8_33 and P8_35:

config-pin P8.33 qep 
config-pin P8.35 qep

Enable eqep2 for pins P8_11 and P8_11:

config-pin P8.11 qep 
config-pin P8.12 qep 

eqep0 position:

cat /sys/devices/platform/ocp/48300000.epwmss/48300180.eqep/position

eqep1 position:

cat /sys/devices/platform/ocp/48302000.epwmss/48302180.eqep/position

eqep2 position:

cat /sys/devices/platform/ocp/48304000.epwmss/48304180.eqep/position

I have created a pull request beagleboard/bb.org-overlays#46

Next step is to add eqep0 and eqep1 to the Rotary Encoder class.