Update The snapshots are working. For some unknown reason sysupgrading to a newer build was making the router unstable. But after a factory reset the build became fairly stable. Read Xiaomi WiFi Router 3G - #222 by hammer for details.
Original post below:
Just a little warning as there might me something wrong with the lastest builds for the Xiaomi 3G.
My router was running perfectly for the last 10+ days and tonight i decided to do a new firmware compile as there are some interesting commits like https://git.lede-project.org/?p=source.git;a=commit;h=fa6fd45613d05da96b6733b15f91e51482378bb0
Unfortunately I ended up with a router that was only up and running for a few minutes and then it rebooted. After this happend a few times I decided to sysupgrade (downgrade) to the last build that was running perfectly. I guess the router decided to reboot in the middle of the upgrade procedure which resulted in a router that just went into a constant boot-loop. After a bit of soldering the serial console showed this.
[ 2.577402] # MTK NAND # : Use HW ECC
[ 2.581079] Device not found, ID: c8d1
[ 2.584805] Not Support this Device![ 2.588530] chip_mode=00000001
[ 2.591596] Support this Device in MTK table! c8d1[ 2.596544] [NAND]select ecc bit:4, sparesize :64 spare_per_sector=16
[ 2.603019] nand: device found, Manufacturer ID: 0xc8, Chip ID: 0xd1
[ 2.609339] nand: ESMT NAND 128MiB 3,3V 8-bit
[ 2.613691] nand: 128 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64
[ 2.621254] Scanning device for bad blocks
[ 2.771199] 10 ofpart partitions found on MTD device MT7621-NAND
[ 2.777175] Creating 10 MTD partitions on "MT7621-NAND":
[ 2.782485] 0x000000000000-0x000000080000 : "Bootloader"
[ 2.789219] 0x000000080000-0x0000000c0000 : "Config"
[ 2.795413] 0x0000000c0000-0x000000100000 : "Bdata"
[ 2.801481] 0x000000100000-0x000000140000 : "Factory"
[ 2.807656] 0x000000140000-0x000000180000 : "crash"
[ 2.813968] 0x000000180000-0x0000001c0000 : "crash_syslog"
[ 2.820600] 0x0000001c0000-0x000000200000 : "reserved0"
[ 2.826888] 0x000000200000-0x000000600000 : "kernel_stock"
[ 2.833538] 0x000000600000-0x000000a00000 : "kernel"
[ 2.839547] 0x000000a00000-0x000007f80000 : "ubi"
[ 2.846300] [mtk_nand] probe successfully!
[ 2.851166] Signature matched and data read!
[ 2.855414] load_fact_bbt success 1023
[ 2.859683] libphy: Fixed MDIO Bus: probed
[ 2.933067] libphy: mdio: probed
[ 4.335817] mtk_soc_eth 1e100000.ethernet: loaded mt7530 driver
[ 4.342491] mtk_soc_eth 1e100000.ethernet eth0: mediatek frame engine at 0xbe100000, irq 20
[ 4.352719] NET: Registered protocol family 10
[ 4.358638] NET: Registered protocol family 17
[ 4.363185] 8021q: 802.1Q VLAN Support v1.8
[ 4.370043] UBI: auto-attach mtd9
[ 4.373428] ubi0: attaching mtd9
[ 5.486107] ubi0: scanning is finished
[ 5.505873] ubi0: attached mtd9 (name "ubi", size 117 MiB)
[ 5.511401] ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
[ 5.518241] ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
[ 5.525012] ubi0: VID header offset: 2048 (aligned 2048), data offset: 4096
[ 5.531956] ubi0: good PEBs: 940, bad PEBs: 0, corrupted PEBs: 0
[ 5.537932] ubi0: user volume: 0, internal volumes: 1, max. volumes count: 128
[ 5.545136] ubi0: max/mean erase counter: 4/2, WL threshold: 4096, image sequence number: 719383500
[ 5.554156] ubi0: available PEBs: 916, total reserved PEBs: 24, PEBs reserved for bad PEB handling: 20
[ 5.563454] ubi0: background thread "ubi_bgt0d" started, PID 353
[ 5.563475] hctosys: unable to open rtc device (rtc0)
[ 5.574963] VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6
[ 5.582439] Please append a correct "root=" boot option; here are the available partitions:
[ 5.590800] 1f00 512 mtdblock0 [ 5.594791] (driver?)
[ 5.597143] 1f01 256 mtdblock1 [ 5.601149] (driver?)
[ 5.603503] 1f02 256 mtdblock2 [ 5.607485] (driver?)
[ 5.609834] 1f03 256 mtdblock3 [ 5.613834] (driver?)
[ 5.616187] 1f04 256 mtdblock4 [ 5.620169] (driver?)
[ 5.622542] 1f05 256 mtdblock5 [ 5.626526] (driver?)
[ 5.628876] 1f06 256 mtdblock6 [ 5.632875] (driver?)
[ 5.635228] 1f07 4096 mtdblock7 [ 5.639210] (driver?)
[ 5.641583] 1f08 4096 mtdblock8 [ 5.645568] (driver?)
[ 5.647917] 1f09 120320 mtdblock9 [ 5.651917] (driver?)
[ 5.654269] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
[ 5.664701] Rebooting in 1 seconds..
Using uboot console I was able to boot the stock kernel and then flash the stock firmware using the recovery mode of the stock kernel. After this I have installed my last working LEDE build and I'm up and running again.