Stuck with applying the device tree overlay file (dtbo) On BeagleBoard-XM, any suggestions how?

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1

Hi There,
I have recently took my Beagleboard-xM and put on it the Ubuntu 14.04 LTS (3.14.2-armv7-x5),
then I tried to mux PIn3 (GPIO_139), after reading thoroughly the pages from both the “System Reference Manual”(Page 110) and the “Technical Reference Manual” of the processor (Pages 2444-2453).
So I wrote the dts file and compiled it via dtc.

but now I got stuck how do I apply the changes on runtime?

I saw on the beaglebone there is a slots file (/sys/devices/…/slots) which was triggering the change,
after we echoed to it the dtbo file. but in my case we are talking about beagleboard-xM which there is no such kind of file.
can someone elaborate what should I do?

Any suggestion would be great! thank you all.

Gil

2

Modify the base dtb file, the capemgr wasn't ported to the xM. When
overlay's hit mainline we will visit this again.

Regards,

3

Wow, thank you Robert for the super quick answer :slight_smile:

A short question before I’ll read and delve into more depth about the subject:
I have noticed during the boot process, the beagleboard-xM (rev B) prints on screen:

"reading /dtbs/omap3-beagle-xm-ab.dtb
60695 bytes read in 13 ms (4.5 MiB/s)

Error: “expansion_args” not defined

Kernel image @ 0x80300000 [ 0x000000 - 0x3e2f38 ]

Flattened Device Tree blob at 815f0000

Booting using the fdt blob at 0x815f0000
Using Device Tree in place at 815f0000, end 81601d16

Starting kernel …"

So I searched for the omap3-beagle-xm-ab.dts (on linux_kernel-3.14.4 source) in order to modify it. but couldn’t find it, found only omap3-beagle-xm.dts
googled and found only this skinny file: omap3-beagle-xm-ab.dts, which contains:

/include/ “omap3-beagle-xm.dts”

/* On Rev A/B USBHOST_PWR_EN is active high */

&hsusb2_power {

enable-active-high;

};

Is it the correct file? which I should:

  1. modify
  2. compile it to dtb
  3. overwrite the exist file in /boot/uboot/dtbs/omap3-beagle-xm-ab.dtb

Thank you again.

Have a great week!

4

Wow, thank you Robert for the super quick answer :slight_smile:

A short question before I'll read and delve into more depth about the
subject:
I have noticed during the boot process, the beagleboard-xM (rev B) prints
on screen:

"reading /dtbs/omap3-beagle-xm-ab.dtb
60695 bytes read in 13 ms (4.5 MiB/s)
## Error: "expansion_args" not defined

That's just an old variable in u-boot for the old "board" file boot. (the
buddy=spidev etc crap)

Kernel image @ 0x80300000 [ 0x000000 - 0x3e2f38 ]
## Flattened Device Tree blob at 815f0000
   Booting using the fdt blob at 0x815f0000
   Using Device Tree in place at 815f0000, end 81601d16

Starting kernel .."

So I searched for the omap3-beagle-xm-ab.dts (on linux_kernel-3.14.4
source) in order to modify it. but couldn't find it, found only
omap3-beagle-xm.dts
googled and found only this skinny file: omap3-beagle-xm-ab.dts, which
contains:

Yeah, just got merged to mainline a few weeks back.

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/omap3-beagle-xm-ab.dts?id=refs/tags/v3.15-rc5

/include/ "omap3-beagle-xm.dts"

/* On Rev A/B USBHOST_PWR_EN is active high */

&hsusb2_power {

    enable-active-high;

};

Is it the correct file? which I should:
1) modify
2) compile it to dtb
3) overwrite the exist file in /boot/uboot/dtbs/omap3-beagle-xm-ab.dtb

It's actually way easier to just "decompile" it with dtc, then recompile it
again.

dtc -I dtb -O dts omap3-beagle-xm-ab.dtb > omap3-beagle-xm-ab.dts

Regards,

5

Thank you, definitely valuable tips! :slight_smile:

6

Gilco, could you post the code you ended up using to get this to work? I am in the same boat, I just want to use some GPIO pins for basic I/O but this new device tree thing is making it hard. Cannot find any information on how to simply export a few pins.
I would really appreciate any help!
~Dagaen Golomb