This procedure backs up your router configuration and then tests that the new trunk firmware can be installed into a US region locked Archer C7.

First, download all of the required files to your computer, these instructions assume you are running on linux of some type.

Create a directory where you can store the files and download the files used in this procedure

wget https://zioncluster.ca/openwrt/archer-c7/us-revert/instructions.txt https://zioncluster.ca/openwrt/archer-c7/us-revert/archer-c7-us-151014-openwrt-recovery.bin https://zioncluster.ca/openwrt/archer-c7/us-revert/ath10k-firmware-qca988x_2014-11-13-77f72b5f7dd940386d9e619a17904987759b7186-1_ar71xx.ipk https://zioncluster.ca/openwrt/archer-c7/us-revert/kmod-ath10k_3.18.29+2016-01-10-1_ar71xx.ipk https://zioncluster.ca/openwrt/archer-c7/us-revert/openwrt-15.05.01-archer-c7.bin https://zioncluster.ca/openwrt/archer-c7/us-revert/openwrt-ar71xx-generic-archer-c7-v2-squashfs-factory.bin

Here's the list of files and their usage:

instructions.txt - These instructions
archer-c7-us-151014-openwrt-recovery.bin - Header stripped stock US firmware
openwrt-ar71xx-generic-archer-c7-v2-squashfs-factory.bin - trunk compile with new US compatible headers
ath10k-firmware-qca988x_2014-11-13-77f72b5f7dd940386d9e619a17904987759b7186-1_ar71xx.ipk - firmware for ath10k on 15.05.1
kmod-ath10k_3.18.29+2016-01-10-1_ar71xx.ipk - kernel module for ath10k on 15.05.1
openwrt-15.05.01-archer-c7.bin - my build of 15.05.1 with support for the new flash chip

Now we're going to backup your configuration.

ssh root@192.168.1.1 "cd /; tar czf - /etc/config" > config-backup.tar.gz

You should now have a local backup file, let's check it.

tar tf config-backup.tar.gz

You should see a list of files similar to the following output.

johnf@johnf-T420s:~/src/openwrt/archer-c7/us-revert$ tar tf config-backup.tar.gz 
etc/config/
etc/config/dhcp
etc/config/dropbear
etc/config/firewall
etc/config/system
etc/config/luci
etc/config/rpcd
etc/config/ubootenv
etc/config/network
etc/config/ucitrack
etc/config/uhttpd
etc/config/wireless

We'll now load the stock US firmware onto the device, this is a modified file with the bootloader header removed.

scp archer-c7-us-151014-openwrt-recovery.bin root@192.168.1.1:/tmp/

We can now install the file on the router running the following command:

sysupgrade /tmp/archer-c7-us-151014-openwrt-recovery.bin

Refresh your DHCP lease and use your web browser to access 192.168.0.1. Install the file US compatible file ( openwrt-ar71xx-generic-archer-c7-v2-squashfs-factory.bin ). You should be able to install this file via the factory web interface.

Once the router reboots you can connect using passwordless ssh. You can upgrade to my build of upstream 15.05.1.

scp openwrt-15.05.01-archer-c7.bin root@192.168.1.1:/tmp/

sysupgrade /tmp/openwrt-15.05.01-archer-c7.bin

You'll need to telnet in and set a password with passwd. (15.05.1, unlike trunk, requires telnet to set the initial password)

Then you can use scp to push in the ath10k drivers:

scp kmod-ath10k_3.18.29+2016-01-10-1_ar71xx.ipk ath10k-firmware-qca988x_2014-11-13-77f72b5f7dd940386d9e619a17904987759b7186-1_ar71xx.ipk root@192.168.1.1:/tmp/

And install them on the router:

opkg install /tmp/ath10k-firmware-qca988x_2014-11-13-77f72b5f7dd940386d9e619a179049
87759b7186-1_ar71xx.ipk /tmp/kmod-ath10k_3.18.29\+2016-01-10-1_ar71xx.ipk 

Now you can update and install the web ui:

opkg update; opkg install luci

And, finally, restore your configuration

scp config-backup.tar.gz root@192.168.1.1:/tmp/

cd /
tar xzf /tmp/config-backup.tar.gz 
reboot

Your router should be back in it's original state.