Debrick, flash firmware for buffalo wzr-hp-ag300h router

Via TFTP on Linux (Ubuntu): 

Please follow the instruction on openwrt's wiki site:
http://wiki.openwrt.org/toh/buffalo/wzr-hp-ag300h#installation.using.the.tftp.method

 But please note the following:
- Use a hardware switch between your computer and your ag300h. From your computer plug an Ethernet cable directly to the port 1 of the switch. From the port 2 of the switch, connect it with the ag300h by Ethernet cable.
- For the ag300h you should only wait for 5s (instead of 10s) after power on the device to enter the tftp put command.
- If all settings are done but you still get the timeout error when put the file, close your terminal window, start a new one and try again.
- The ag300h for the Japan market has different region in u-boot so you can't install dd-wrt or other English stock firmware (come from buffalotech.com). You must unbox your router, use terminal console to change its region first. Please read carefully the instruction on the wiki above.

*If the bootloader of your router was broken and you can't use tftp to access via u-boot, you must use another way to recover it. You can use a serial console (TTL USB) to do so. The following instruction for the WZR-HP-G300NH but it maybe similar for the AG300H and it's a good reference for now.
http://scarygliders.net/2010/02/23/hacking-around-the-japanese-buffalo-wzr-hp-g300n/

Hopefully this helps some people.