CODEWITHSUNDEEP
beagleboardgpioangstrom-linuxdevice-tree
Don Branson
Don Branson

Reputation: 13707

BBB - Automatically load a Device Tree overlay on boot

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.

Upvotes: 4

Views: 12055

Answers (3)

Katu
Katu

Reputation: 1564

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

Upvotes: 0

MolhamStein
MolhamStein

Reputation: 627

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

Upvotes: 3

TheCodeArtist
TheCodeArtist

Reputation: 22507

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.

Upvotes: 3

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