BBB - Automatically load a Device Tree overlay on boot

Question

I have a device tree overlay:

/dts-v1/;
/plugin/;

/ {
    compatible = "ti,beaglebone", "ti,beaglebone-black";
    part-number = "mousetraps";
    version = "00A1";

    /* https://github.com/derekmolloy/boneDeviceTree/blob/master/docs/BeagleboneBlackP9HeaderTable.pdf */
    fragment@0 {
            target = <&am33xx_pinmux>;
            __overlay__ {
                    mousetrap_pins: pinmux_mousetrap_pins {
                            pinctrl-single,pins = <
                                    0x070 0x2f /* P9_11 30 INPUT MODE7 none */
                                    0x074 0x2f /* P9_13 31 INPUT MODE7 none */
                                    0x040 0x2f /* P9_15 48 INPUT MODE7 none */
                                    0x15c 0x2f /* P9_17 05 INPUT MODE7 none */
                            >;
                    };
            };
    };

    fragment@1 {
            target = <&ocp>;
            __overlay__ {
                    test_helper: helper {
                            compatible = "bone-pinmux-helper";
                            pinctrl-names = "default";
                            pinctrl-0 = <&mousetrap_pins>;
                            status = "okay";
                    };
            };
    };
};

which I can successfully load with:

echo mousetraps:00A1 >/sys/devices/bone_capemgr.8/driver/bone_capemgr.8/slots ; dmesg | grep bone

How can I configure the BBB/Angstrom to load it automatically on boot?

More specifically, how can I hook the dtbo file into the normal Device Tree loading mechanism? I know I can add the echo to a linux init script, but it seems like there must be something that triggers the loading of the dtbo files.

score 3 · Answer 1 · answered Jul 22 '13 at 09:36

One way to do this would be to copy the dtbo into /lib/firmware and modify capemgr.extra_override parameter in the kernel bootargs (in uEnv.txt) to point to the dtbo file. This technique also requires modifications to the /arch/arm/boot/dts/am335-bone-common.dtsi file. Details in this discussion.

Note that loading the device-tree overlay from the filesystem seems to be an issue specifically with the recent kernels(from the official repository) on the beaglebone black. To overcome this, an alternate method to compile the overlay is described here.

Regarding the issue with loading the device tree overlay at boot time—see [FBTFT BeagleBone Black—Enable overlay at boot](https://github.com/notro/fbtft/wiki/BeagleBone-Black#enable-overlay-at-boot). — Craig McQueen, Jan 28 '15 at 05:16

score 3 · Answer 2 · answered Oct 15 '13 at 14:57

3

you may add an argument in the uEnv.txt that refers to your new overlay as suggested previously add the following string to the end of the uEnv.txt

nano /mnt/boot/uEnv.txt

#add this to the end of the single line of uEnv.txt:

capemgr.enable_partno=mousetraps

the full process is described here

answered Oct 15 '13 at 14:57

MolhamStein

617
8
14

1

One thing you should not forget, when using Debian I needed to add the option to the capemgr file: `nano /etc/default/capemgr` And then in your situation, add: `CAPE=mousetraps:00A1` Ps. On a beaglebone the version is often: "00A0". – Melroy van den Berg Sep 05 '15 at 13:14

score 0 · Answer 3 · answered Jun 02 '17 at 14:44

This worked for me with

BeagleBone Black rev C
Debian 8.7 2017-03-19 4GB SD IoT from latest-images
Kernel 4.4.68-ti-r106

From the link provided by @craig-mcqueen and using this device tree overlay example

In the /boot/uboot/uEnv.txt file (DM-GPIO-Test is the name of my overlay):

cmdline=coherent_pool=1M cape_universal=enable bone_capemgr.enable _partno=DM-GPIO-Test noapic

Create /etc/initramfs-tools/hooks/dtbo

#!/bin/sh
set -e
. /usr/share/initramfs-tools/hook-functions

# Copy Device Tree fragments
mkdir -p "${DESTDIR}/lib/firmware"
cp -p /lib/firmware/*.dtbo "${DESTDIR}/lib/firmware/"

Make it executable:

sudo chmod +x /etc/initramfs-tools/hooks/dtbo

Backup initrd:

sudo cp /boot/initrd.img-4.4.68-ti-r106 /boot/initrd.img-4.4.68-ti-r106.bak

Update initrd:

/opt/scripts/tools/developers/update_initrd.sh

Reboot

sudo reboot

Check that it's been loaded:

root@beaglebone:/home/debian# 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,DM-GPIO-Test

BBB - Automatically load a Device Tree overlay on boot

3 Answers3