/sys/kernel/debug/omap_mux do not exist

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1

Hi. Mi name is Rodrigo and I was searching for hours the problem in google, but I didn’t found :frowning:

I have a beagleboard xM with Angstrom running in it. I need to change the mux to use uart 1 and 2, and I read in several places that it is posible writing files in /sys/kernel/debug/omap_mux. However, when I mount debugfs with:

mount -t debugfs none /sys/kernel/debug

omap_mux do not appears.

ls /sys/kernel/debug

asoc clock hid omapdss sched_features usb
bdi gpio mmc0 pm_debug tracing vram

Any idea? If somebody need more information, please let me know.

Thanks.

2

Nobody had the same problem? Any idea?

Thanks

3

Rodrigo,

What version of the kernel are you using? Are you using an Angstrom demo image (e.g. downloaded from http://downloads.angstrom-distribution.org/demo/beagleboard/) or did you build a kernel from source?

I think that older versions of the kernel don’t support the omap_mux file system. If you built the kernel from source then there are probably build options that you need to add, but I’ve never done that myself.

Dan.

4

You need to mount the debug file system: mount -t debugfs none /sys/kernel/debug

Better still, do it in /etc/fstab by adding: debugfs /sys/kernel/debug debugfs 0 0

Mike

5

Mike, I had been mounted debugfs and the content is (as I showed in the previous message):

ls /sys/kernel/debug

asoc clock hid omapdss sched_features usb
bdi gpio mmc0 pm_debug tracing vram

Dan, mi kernel version:

Linux version 2.6.32 (koen@dominion) (gcc version 4.3.3 (GCC) ) #3 PREEMPT Tue Jul 26 10:56:56 CEST 2011
Do you know if it is an older version to omap_mux?

I am using the demo version that bring with beagleboard-xM rev. C.

Thanks to both the cooperation :stuck_out_tongue:

6

Rodrigo,

I don’t know for sure that the omap_mux file system is unavailable with that kernel, but I’ve only used omap_mux with kernel version 3 and later.

So, if you can easily switch to a new image, I would suggest you download an Angstrom demo image from http://downloads.angstrom-distribution.org/demo/beagleboard/.

I’m currently running Ubuntu on my own BB-XM, with kernel 3.2.13, and omap_mux is definitely there (without having to manually mount it). However, I was previously running one of the Angstrom demo images (I think it was Angstrom-TI-GNOME-image-eglibc-ipk-v2012.01-core-beagleboard-2012.01.11.img.gz, kernel version 3.something), and omap_mux was available there too.

Dan.

7

Hi Dan,

I will try with a new image as you suggest and then I comment what happend.

Thanks

8

I tried the demo image called Angstrom-systemd-image-eglibc-ipk-v2012.01-core-beagleboard.rootfs.tar.bz2 with the Kernel 3.0.17 and /sys/kernel/debug/omap_mux is there :stuck_out_tongue:

Thanks a lot Dan

Additionaly, I like to comment that I found another alternative to mux uarts (at least uart2).
In the beagleboard xM revC with Angstrom (kernel 2.6.32):

root@beagleboard:~# devmem2 0x48002178 h 0x0000
root@beagleboard:~# devmem2 0x48002172 h 0x0101

With these command uart2 work. devmem2 read/write /dev/mem. I read that only work with kernels older than 2.6.39.
For uart1, the commands could be:

root@beagleboard:~# devmem2 0x480020E8 h 0x0002
root@beagleboard:~# devmem2 0x480020EA h 0x0102

but it didn’t work for me :frowning:

The address (0x4800XXXX) can be obtained from AM/DM37x Technical Reference Manual (http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=sprugn4p&fileType=pdf).
Note: when a register use the upper bits ([31:15]) the base address + 2 must be used.

Thanks again and success.

9

Where did you get that image? I’m currrently using ubuntu 13.04 arm from elinux method 1 and when I run mount -t debugfs none /sys/kernel/debug it says none is already mounted. When I add debugfs /sys/kernel/debug debugfs 0 0 to my fstab it doesn’t change anything. When I run uname -r it says 3.8.8-bone14.

Will your image be compatible with the new BB black?

10

This doesn’t work on my ubuntu install from elinux method 1. It is ubuntu 13.04 kernal: 3.8.8-bone14 at least that is the output from uname -r.

This is the output from mount

mount: none already mounted or /sys/kernel/debug busy
mount: according to mtab, none is already mounted on /sys/kernel/debug