I have flashed OpenWRT to a Buffalo BHR 4GRV, and it works reasonably well.
However, after I have tried to re-flash it to Stock or DD-WRT image, it fails miserably.
With the stock image flashed over console/WebUISERIAL/... I get "Bad Magic Number", after re-flashing an older DD-WRT image to it, I get segmentation fault:
BUFFALO U-BOOT Ver 1.00
== CPU:400MHz, DDR:400MHz, AHB:200MHz ==
AP111 (ar7241 - Virian) U-boot
DRAM: 64 MB
WAN port disabling: done
Top of RAM usable for U-Boot at: 84000000
Reserving 257k for U-Boot at: 83fbc000
Reserving 192k for malloc() at: 83f8c000
Reserving 44 Bytes for Board Info at: 83f8bfd4
Reserving 36 Bytes for Global Data at: 83f8bfb0
Reserving 128k for boot params() at: 83f6bfb0
Stack Pointer at: 83f6bf98
Now running in RAM - U-Boot at: 83fbc000
flash bank #0 found 16 MB flash [W25Q128BV, blk:0x10000, sectors:256]
flash bank #1 found 16 MB flash [W25Q128BV, blk:0x10000, sectors:256]
Flash: 32 MB
*** Warning *** : PCIe WLAN Module not found !!!
In: serial
Out: serial
Err: serial
Memory Test (address line)
uboot use 83F6BFB0 - 84000000
Memory Test start(0x80000000) end(0x83F00000) size(67108864)
Data line test start:0x80000000 pattern 0x00000001 0x00000003 0x00000007 0x0000000F 0x00000005 0x00000015 0x00000055 0xAAAAAAAA
Address line test start:0x80000000 len:0x3f00000 pattern 0xAAAAAAAA 0x55555555
Fill test patnum:5
fill Pattern 5555AAAA Writing... Reading...
fill Pattern AAAA5555 Writing... Reading...
fill Pattern 0000FFFF Writing... Reading...
fill Pattern FFFF0000 Writing... Reading...
fill Pattern AAAAAAAA Writing... Reading...
Memory Test OK
### buf_ver=[1.00] U-Boot Ver.=[1.00]
### build_date(env)=[Apr 6 2011 - 08:52:25] build_date(bin)=[Apr 6 2011 - 08:52:25]
ag7240_enet_initialize...
Reading MAC Address from ENV(0x83f8c319)
No valid address in Flash. Using fixed address
Virian MDC CFG Value ==> 4
: cfg1 0x7 cfg2 0x7114
eth0: 02:aa:bb:cc:dd:22
athrs16_reg_init: complete
eth0 up
Virian MDC CFG Value ==> 4
: cfg1 0xf cfg2 0x7214
eth1: 00:03:7f:09:0b:ad
eth1 up
eth0 02:AA:BB:CC:DD:22
, eth1 00:03:7F:09:0B:AD
dup 1 speed 1000
tftp server(receive) go, waiting:4[sec]
Load address: 0x81f00000
TftpServer Timeout;
no file was loaded.
LAN port disabling: done
## Checking Image at bf060000 ...
Image Name: DD-WRT v24 Linux Kernel Image
Created: 2014-04-25 11:52:33 UTC
Image Type: MIPS Linux Kernel Image (lzma compressed)
Data Size: 1228245 Bytes = 1.2 MB
Load Address: 80060000
Entry Point: 800646d0
Verifying Checksum ... crc32_fw: bf060040 - bf18be14 (len:0012bdd5) calc...
crc32_fw: range1 bf060040 - bf18be14
OK
change bootargs
console=ttyS0,115200 root=31:03 rootfstype=jffs2 init=/sbin/init mtdparts=ar7240-nor0:256k(u-boot),64k(u-boot-env),1152k@384k(uImage),6592k@1536k(rootfs),64k@320k(ART),64k@8128k(properties),8192k@8192k(flash1),16384k@16384k(flash2) mem=64M
## Booting image at bf060000 ...
Image Name: DD-WRT v24 Linux Kernel Image
Created: 2014-04-25 11:52:33 UTC
Image Type: MIPS Linux Kernel Image (lzma compressed)
Data Size: 1228245 Bytes = 1.2 MB
Load Address: 80060000
Entry Point: 800646d0
Uncompressing Kernel Image ... OK
No initrd
## Transferring control to Linux (at address 800646d0) ...
## Giving linux memsize in bytes, 67108864
Starting kernel ...
[ 0.000000] bootconsole [early0] enabled
[ 0.000000] CPU revision is: 00019374 (MIPS 24Kc)
AR7242
detect mem size
Uart Init
Booting AR7240(Python)...
[ 0.000000] sys id = 1101 Atheros AR7242 rev 1.1 (0x1101)
[ 0.000000] Determined physical RAM map:
[ 0.000000] memory: 04000000 @ 00000000 (usable)
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x00000000-0x03ffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x00000000-0x03ffffff]
[ 0.000000] Primary instruction cache 64kB, 4-way, VIPT, I-cache aliases, linesize 32 bytes.
[ 0.000000] Primary data cache 32kB, 4-way, VIPT, cache aliases, linesize 32 bytes
[ 0.000000] Linux version 3.9.11 (root@dd-wrt.buildserver) (gcc version 4.8.3 (OpenWrt/Linaro GCC 4.8-2014.01 r39555) ) #57 Mon Apr 14 13:59:27 CEST 2014
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 16256
[ 0.000000] Kernel command line: console=ttyS0,115200 root=1f02 rootfstype=squashfs noinitrd init=/sbin/init
[ 0.000000] PID hash table entries: 256 (order: -2, 1024 bytes)
[ 0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
[ 0.000000] __ex_table already sorted, skipping sort
[ 0.000000] Writing ErrCtl register=00000000
[ 0.000000] Readback ErrCtl register=00000000
[ 0.000000] Memory: 60836k/65536k available (2476k kernel code, 4700k reserved, 754k data, 224k init, 0k highmem)
[ 0.000000] NR_IRQS:80
[ 0.000000] Calibrating delay loop... 265.42 BogoMIPS (lpj=1327104)
[ 0.080000] pid_max: default: 32768 minimum: 301
[ 0.080000] Mount-cache hash table entries: 512
[ 0.090000] NET: Registered protocol family 16
[ 0.340000] PCI: no PCIe module found
[ 0.360000] bio: create slab <bio-0> at 0
[ 0.360000] usbcore: registered new interface driver usbfs
[ 0.370000] usbcore: registered new interface driver hub
[ 0.370000] usbcore: registered new device driver usb
[ 0.380000] Switching to clocksource MIPS
[ 0.380000] NET: Registered protocol family 2
[ 0.390000] TCP established hash table entries: 512 (order: 0, 4096 bytes)
[ 0.390000] TCP bind hash table entries: 512 (order: -1, 2048 bytes)
[ 0.400000] TCP: Hash tables configured (established 512 bind 512)
[ 0.400000] TCP: reno registered
[ 0.410000] UDP hash table entries: 256 (order: 0, 4096 bytes)
[ 0.410000] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[ 0.420000] NET: Registered protocol family 1
[ 0.420000] gpio_proc: module loaded and /proc/gpio/ created
[ 0.430000] squashfs: version 3.0 (2006/03/15) Phillip Lougher
[ 0.440000] msgmni has been set to 118
[ 0.440000] alg: No test for stdrng (krng)
[ 0.450000] io scheduler noop registered
[ 0.450000] io scheduler deadline registered (default)
[ 0.460000] Serial: 8250/16550 driver, 1 ports, IRQ sharing disabled
[ 0.490000] serial8250.0: ttyS0 at MMIO 0x18020000 (irq = 11) is a 16550A
[ 0.490000] console [ttyS0] enabled, bootconsole disabled
[ 0.490000] console [ttyS0] enabled, bootconsole disabled
[ 0.510000] check spi banks 2
[ 0.510000] 0000 : EF 40 18
[ 0.510000] found W25Q128BV device on bank#0
[ 0.520000] 0000 : EF 40 18
[ 0.520000] found W25Q128BV device on bank#1
[ 0.520000] SPI flash size total:32 Mbytes
[ 0.610000]
[ 0.610000] found squashfs at 18C000
[ 0.610000] Creating 9 MTD partitions on "ar7240-nor0":
[ 0.620000] 0x000000000000-0x000000050000 : "RedBoot"
[ 0.620000] 0x000000060000-0x000001fe0000 : "linux"
[ 0.630000] 0x00000018c000-0x000001440000 : "rootfs"
[ 0.630000] mtd: partition "rootfs" must either start or end on erase block boundary or be smaller than an erase block -- forcing read-only
[ 0.650000] mtd: partition "rootfs" set to be root filesystem
[ 0.650000] 0x000001440000-0x000001fe0000 : "ddwrt"
[ 0.660000] 0x000001fe0000-0x000001ff0000 : "nvram"
[ 0.670000] 0x000001ff0000-0x000002000000 : "FIS directory"
[ 0.670000] 0x000001ff0000-0x000002000000 : "board_config"
[ 0.680000] 0x000000000000-0x000002000000 : "fullflash"
[ 0.690000] 0x000000040000-0x000000050000 : "uboot-env"
[ 0.700000] tun: Universal TUN/TAP device driver, 1.6
[ 0.700000] tun: (C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>
[ 0.910000] PPP generic driver version 2.4.2
[ 0.910000] PPP BSD Compression module registered
[ 0.920000] PPP Deflate Compression module registered
[ 0.920000] PPP MPPE Compression module registered
[ 0.930000] NET: Registered protocol family 24
[ 0.950000] u32 classifier
[ 0.950000] Performance counters on
[ 0.950000] input device check on
[ 0.960000] Actions configured
[ 0.960000] Netfilter messages via NETLINK v0.30.
[ 0.960000] nf_conntrack version 0.5.0 (950 buckets, 3800 max)
[ 0.970000] nf_conntrack_rtsp v0.6.21 loading
[ 0.980000] nf_nat_rtsp v0.6.21 loading
[ 0.980000] ip_tables: (C) 2000-2006 Netfilter Core Team
[ 0.980000] IPP2P v0.8.2 loading
[ 0.990000] TCP: westwood registered
[ 0.990000] TCP: hybla registered
[ 1.000000] TCP: vegas registered
[ 1.000000] NET: Registered protocol family 17
[ 1.000000] Bridge firewalling registered
[ 1.010000] 8021q: 802.1Q VLAN Support v1.8
[ 1.010000] searching for nvram
[ 1.020000] nvram size = 0
[ 1.090000] Broken NVRAM found, recovering it (Magic FFFFFFFF)
[ 1.100000] Atheros AR71xx hardware watchdog driver version 0.1.0
[ 1.100000] ar71xx-wdt: timeout=15 secs (max=21) ref freq=200000000
[ 1.110000] VFS: Mounted root (squashfs filesystem) readonly on device 31:2.
[ 1.120000] Freeing unused kernel memory: 224k freed
start service
starting Architecture code for wzrg450
starting hotplug
Jan 1 00:00:02 udevtrigger[242]: parse_config_file: can't open '/etc/udev/udev.conf' as config file: No such file or directory
start MSTP Daemon
1970-01-01 00:00:04 main: Sanity checks succeeded
done
load ag71xx or ag7100_mod Ethernet Driver
[ 4.650000] switch0: Atheros AR8316 switch registered on ag71xx-mdio.0
[ 4.650000] libphy: ag71xx_mdio: probed
[ 4.660000] eth0: Atheros AG71xx at 0xb9000000, irq 4, mode:RGMII
[ 5.220000] ar8316: Using port 4 as switch port
[ 5.720000] ag71xx ag71xx.0 eth0: connected to PHY at ag71xx-mdio.0:00 [uid=004dd041, driver=Atheros AR8216/AR8236/AR8316]
configure eth0 to 4C:E6:76:EA:BD:5D
configure vlan1 to 4C:E6:76:EA:BD:5D
configure vlan2 to 4C:E6:76:EA:BD:5D
ifconfig: SIOCSIFHWADDR: Device or resource busy
load ATH 802.11 a/b/g Driver
insmod: ath_hal.ko: module not found
insmod: ath_pci.ko: module not found
insmod: ath_ahb.ko: module not found
load ATH9K 802.11n Driver
[ 7.030000] Loading modules backported from Linux version master-2013-06-27-0-gdcfa6d5
[ 7.030000] Backport generated by backports.git backports-20130617-4-ge3220f5
insmod: compat_firmware_class.ko: module not found
[ 7.220000] cfg80211: Calling CRDA to update world regulatory domain
[ 7.230000] cfg80211: World regulatory domain updated:
[ 7.230000] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[ 7.240000] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[ 7.250000] cfg80211: (2457000 KHz - 2482000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[ 7.260000] cfg80211: (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[ 7.270000] cfg80211: (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[ 7.270000] cfg80211: (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Segmentation fault
[USB] checking...
umount: can't umount /mnt: No such file or directory
rmmod: usblp: No such file or directory
rmmod: printer: No such file or directory
rmmod: usb-storage: No such file or directory
rmmod: sr_mod: No such file or directory
rmmod: cdrom: No such file or directory
rmmod: sd_mod: No such file or directory
rmmod: scsi_wait_scan: No such file or directory
rmmod: scsi_mod: No such file or directory
rmmod: usbmisc_imx: No such file or directory
rmmod: ci13xxx_imx: No such file or directory
rmmod: ci_hdrc: No such file or directory
rmmod: phy-mxs-usb: No such file or directory
rmmod: fsl-mph-dr-of: No such file or directory
rmmod: usb-libusual: No such file or directory
rmmod: dwc_otg: No such file or directory
rmmod: xhci-hcd: No such file or directory
rmmod: usb-ohci: No such file or directory
rmmod: ohci-hcd: No such file or directory
rmmod: uhci-hcd: No such file or directory
rmmod: usb-uhci: No such file or directory
rmmod: ehci-pci: No such file or directory
rmmod: ehci-platform: No such file or directory
rmmod: ehci-hcd: No such file or directory
rmmod: fsl-mph-dr-of: No such file or directory
rmmod: usbcore: No such file or directory
rmmod: usb-common: No such file or directory
rmmod: xfs: No such file or directory
rmmod: msdos: No such file or directory
rmmod: vfat: No such file or directory
rmmod: fat: No such file or directory
rmmod: nls_utf8: No such file or directory
rmmod: nls_iso8859-2: No such file or directory
rmmod: nls_iso8859-1: No such file or directory
rmmod: nls_cp437: No such file or directory
rmmod: nls_cp932: No such file or directory
rmmod: nls_cp936: No such file or directory
rmmod: nls_cp950: No such file or directory
rmmod: nls_base: No such file or directory
rmmod: ext3: No such file or directory
rmmod: jbd: No such file or directory
rmmod: ext2: No such file or directory
rmmod: mbcache: No such file or directory
rmmod: fuse: No such file or directory
Segmentation fault
[ 8.750000] eth0: link up (1000Mbps/Full duplex)
[ 9.370000] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[ 9.370000]
It is strange, that it tries to init WLAN (fails, it is not available for the router), and then it does not find any kmod files. Am I doing something wrong? (Sure, I am 
)
What should be the way to get back to Stock or at least change to DD-WRT?
I need to create a tool, that automates the firmware update to openwrt, but I would need an initial state to test... 
I have even pulled an MTD backup from another one, but the image is about 33MB, and I don't even have that much space on the device after a clean flash. I have tried to flash it from USB storage with mtd write firmware_mtd_backup.bin firmware, but that did not work either:
Unlocking firmware ...
Writing from mtd1_linux.backup to firmware ... [w][ 2483.510094] SQUASHFS error: Failed to read block 0x38daac: -5
[ 2483.515898] SQUASHFS error: Unable to read metadata cache entry [38daaa]
[ 2483.522712] SQUASHFS error: read_indexes: reading block [38daaa:5f]
[ 2483.529117] SQUASHFS error: Unable to read metadata cache entry [38daaa]
[ 2483.535860] SQUASHFS error: read_indexes: reading block [38daaa:5f]
[ 2483.542224] SQUASHFS error: Unable to read metadata cache entry [38daaa]
[ 2483.548979] SQUASHFS error: read_indexes: reading block [38daaa:5f]
[ 2483.555339] SQUASHFS error: Unable to read metadata cache entry [38daaa]
[ 2483.562101] SQUASHFS error: read_indexes: reading block [38daaa:5f]
Rebooting ...
[ 2540.081827] SQUASHFS error: Unable to read metadata cache entry [38daaa]
[ 2540.088717] SQUASHFS error: read_indexes: reading block [38daaa:5f]
[ 2540.095076] SQUASHFS error: Unable to read metadata cache entry [38daaa]
[ 2540.101881] SQUASHFS error: read_indexes: reading block [38daaa:5f]
[ 2542.109887] Deleting MTD partitions on "spi0.0":
[ 2542.117969] Removing MTD device #0 (spi0.0) with use count 1
[ 2542.124212] Deleting MTD partitions on "spi0.1":
[ 2542.133078] SQUASHFS error: Unable to read metadata cache entry [38daaa]
[ 2542.139932] SQUASHFS error: read_indexes: reading block [38daaa:5f]
[ 2542.146312] SQUASHFS error: Unable to read metadata cache entry [38daaa]
[ 2542.153052] SQUASHFS error: read_indexes: reading block [38daaa:5f]
[ 2542.161906] Removing MTD device #1 (spi0.1) with use count 1
[ 2542.169748] reboot: Restarting system
After that I get back to the above Segmentation fault