Using GPIO-Poweroff on a Raspberry Pi Compute Module with DAS U-Boot to turn off the PSU - linux

Question

I've been trying to get GPIO-Poweroff to switch off the board PSU using GPIO but no matter what I try, it never seems to work. If I manually toggle the GPIO pin, the device immediately shuts down. If I take stock Raspbian-Lite and add the following line to config.txt it works. But U-Boot seems to be ignoring it. I am using Raspbian Lite 2017-07-5 with the latest mainline U-Boot: git://git.denx.de/u-boot.git compiled with rpi_defconfig.
dtoverlay=gpio-poweroff,gpiopin=6,active_low=1
With U-Boot the Raspberry Pi boots and works normally, it even shuts down but it never toggles GPIO6. This leaves the PSU running and the only way to fix it is by holding down the power button for at least 5 seconds. I know that dt-blob.bin is loaded and applied as the board has a camera which only works with the correct dt-blob.bin.
At thus point I am out of ideas. I have tried:
Updating the Linux kernel using rpi-update
Decompiling both gpio-poweroff.dtbo and dt-blob.bin. Changing 0x1a to 0x06 and 0x0 to 0x1 inside gpio -poweroff.dtbo, concatenating them together and it doesn't work.
Manually doing the above and intertwining the decompiled code.
Using fdt addr, and fdt apply inside boot.scr to apply it manually, this didn't work because fdt_overlay_apply FDT_ERR_NOSPACE and I couldn't seem to get past this.
Cloning linux and trying to make dtsb, target doesn't exist.
Cloning linux/arch/arm/boot/dts, writing a MakeFile and compiling them with my changes results in a U-Boot loading, Raspbian loading but gpio-poweroff not working.
Other attempts which are barely worth mentioning.
Nothing I try seems to work, and I'm not sure where to go forward.
For reference, here are some of the files in use:
boot.cmd:
#Setting default bootargs
setenv original_bootargs console=ttyS0 console=tty1 rootfstype=ext4 fsck.repair=yes hdmi.audio=0 disp.screen0_output_mode=1920x1080p60:1280x720p60:800x600p60:EDID rootwait panic=10 # console MUST be ttyS0 or it WILL NOT BOOT!
# Identify if we are using partition 2 or 3
if fatload mmc 0:1 ${loadaddr} swap; then echo "Using Partition 3"; setenv partition 3; else echo "Using Partition 2"; setenv partition 2; fi
# Check for recovery
if fatload mmc 0:1 ${loadaddr} recovery; then echo "Using Recovery Partition"; setenv partition 4; fi
#if gpio input 32 || fatload mmc 0:1 ${loadaddr} recovery; then echo "Using Recovery Partition"; setenv partition 4; fi
# Create an empty file to detect boot failures
fatwrite mmc 0:1 ${kernel_addr_r} recovery 0
# Set bootargs
setenv bootargs "${original_bootargs} root=/dev/mmcblk0p${partition}"
# Load the existing Linux kernel into RAM
echo Loading partition ${partition}
ext4load mmc 0:${partition} ${kernel_addr_r} kernel.img
# Boot the kernel we have just loaded
bootz ${kernel_addr_r} - ${fdt_addr}
Not sure why, but it boots with red and blue swapped, and at a low resolution. Compiled with mkimage -A arm -O linux -T script -C none -a 0x00000000 -e 0x00000000 -n "Boot Script" -d boot.cmd boot.scr
config.txt:
# For more options and information see
# http://rpf.io/configtxt
# Some settings may impact device functionality. See link above for details
# uncomment if you get no picture on HDMI for a default "safe" mode
#hdmi_safe=1
# uncomment this if your display has a black border of unused pixels visible
# and your display can output without overscan
disable_overscan=1
# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
#overscan_left=16
#overscan_right=16
#overscan_top=16
#overscan_bottom=16
# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=1280
#framebuffer_height=720
# uncomment if hdmi display is not detected and composite is being output
#hdmi_force_hotplug=1
# uncomment to force a specific HDMI mode (this will force VGA)
#hdmi_group=1
#hdmi_mode=1
# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2
# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4
# uncomment for composite PAL
#sdtv_mode=2
#uncomment to overclock the arm. 700 MHz is the default.
#arm_freq=800
# Uncomment some or all of these to enable the optional hardware interfaces
dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on
# Uncomment this to enable the lirc-rpi module
#dtoverlay=lirc-rpi
# Additional overlays and parameters are documented /boot/overlays/README
# Enable audio (loads snd_bcm2835)
#dtparam=audio=on
gpu_mem=128
start_x=1
dtoverlay=gpio-poweroff,gpiopin=6,active_low=1
dtdebug=1

Answer 1

So, I've somewhat fixed it by compiling my own bcm27***.dtb files with the following concatenated after their original content:
/ {
compatible = "brcm,bcm2709";
power_ctrl: power_ctrl {
compatible = "gpio-poweroff";
gpios = <&gpio 6 1>;
};
};
However, this has completely broken GPIO and i2c. So this isn't a complete solution. My next step is to restore the original files, and try adding this to the end of dt-blob.bin

Answer 2

I did it, here is the answer:
# Manually apply overlay
setenv fdt_length 50000
setexpr kernel_addr_r ${fdt_addr} + ${fdt_length}
fdt addr ${fdt_addr} # Load the existing tree
fdt boardsetup # Device specific setup
fdt move ${fdt_addr} ${fdt_addr} ${fdt_length} # Resize the loaded fdt to ${fdt_length}
fatload mmc 0:1 ${kernel_addr_r} overlays/gpio-poweroff.dtbo
fdt apply ${kernel_addr_r} # Apply the overlay
Editing default device trees and dt-blob.bin ended being a fruitless endeavour. What you need to do is apply the overlay yourself, manually, inside uboot.src.
The first step is to find the source code of the desired overlay, and change the default value to you desired value, you cannot use overlay arguments inside U-Boot.
Before applying overlays you need to increase the size of the loaded device tree using fdt move, then you can load and apply from fat. If you wanted to apply more overlays you simply need to add additional lines such as:
fatload mmc 0:1 ${kernel_addr_r} overlays/rpi-tv.dtbo
fdt apply ${kernel_addr_r} # Apply the overlay
Be careful your device tree doesn't run out of space!