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Booting Linux on the Mesh Potato

The good news is we have Linux booting on the Mesh Potato:

+Ethernet eth0: MAC address 00:22:b0:42:03:e4
IP:, Gateway:
Default server:

RedBoot(tm) bootstrap and debug environment [ROMRAM]
Non-certified release, version v1.3.0 - built 16:59:11, Jun 8 2009

Copyright (C) 2000, 2001, 2002, 2003, 2004 Red Hat, Inc.

Board: ap61
RAM: 0x80000000-0x81000000, [0x8003dd50-0x80fe1000] available
FLASH: 0xa8000000 - 0xa87e0000, 128 blocks of 0x00010000 bytes each.
== Executing boot script in 5.000 seconds - enter ^C to abort
RedBoot> load openwrt-atheros-vmlinux.elf
Using default protocol (TFTP)
Entry point: 0x801f8850, address range: 0x80041000-0x80262086
RedBoot> go
Linux version (david@bunny) (gcc version 4.1.2) #3 Mon Jun 8 15:07:39 9memcfg: 0x141168 memsize: 0x1000000
CPU revision is: 00019064 (MIPS 4KEc)
Determined physical RAM map:
memory: 01000000 @ 00000000 (usable)
Initrd not found or empty - disabling initrd
Zone PFN ranges:
Normal 0 -> 4096
Movable zone start PFN for each node
early_node_map[1] active PFN ranges
0: 0 -> 4096
Built 1 zonelists in Zone order, mobility grouping off. Total pages: 4064
Kernel command line: console=ttyS0,9600 rootfstype=squashfs,jffs2 init=/etc/pretPrimary instruction cache 16kB, VIPT, 4-way, linesize 16 bytes.
Primary data cache 16kB, 4-way, VIPT, no aliases, linesize 16 bytes
PID hash table entries: 64 (order: 6, 256 bytes)
console [ttyS0] enabled
Dentry cache hash table entries: 2048 (order: 1, 8192 bytes)
Inode-cache hash table entries: 1024 (order: 0, 4096 bytes)
Memory: 13692k/16384k available (1773k kernel code, 2692k reserved, 289k data, )SLUB: Genslabs=6, HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
Mount-cache hash table entries: 512
net_namespace: 644 bytes
NET: Registered protocol family 16
WARNING: broken board data detected
Radio config found at offset 0xf8(0x1f8)
NET: Registered protocol family 2
IP route cache hash table entries: 1024 (order: 0, 4096 bytes)
TCP established hash table entries: 512 (order: 0, 4096 bytes)
TCP bind hash table entries: 512 (order: -1, 2048 bytes)
TCP: Hash tables configured (established 512 bind 512)
TCP reno registered
NET: Registered protocol family 1
ar531x: Registering GPIODEV device
squashfs: version 3.0 (2006/03/15) Phillip Lougher
Registering mini_fo version $Id$
JFFS2 version 2.2. (NAND) (SUMMARY) .. 2001-2006 Red Hat, Inc.
msgmni has been set to 26
io scheduler noop registered
io scheduler deadline registered (default)
gpiodev: gpio device registered with major 254
gpiodev: gpio platform device registered with access mask FFFFFFFF
Serial: 8250/16550 driver $Revision: 1.90 $ 1 ports, IRQ sharing disabled
serial8250: ttyS0 at MMIO 0xb1100003 (irq = 37) is a 16550A
eth0: Atheros AR231x: 00:22:b0:42:03:e4, irq 4
ar2313_eth_mii: probed
eth0: attached PHY driver [Generic PHY] (mii_bus:phy_addr=0:01)
cmdlinepart partition parsing not available
Searching for RedBoot partition table in spiflash at offset 0x7d0000
6 RedBoot partitions found on MTD device spiflash
Creating 6 MTD partitions on "spiflash":
0x00000000-0x00030000 : "RedBoot"
0x00030000-0x000e0000 : "vmlinux.bin.l7"
0x000e0000-0x007d0000 : "rootfs"
mtd: partition "rootfs" set to be root filesystem
mtd: partition "rootfs_data" created automatically, ofs=330000, len=4A0000
0x00330000-0x007d0000 : "rootfs_data"
0x007d0000-0x007df000 : "FIS directory"
0x007df000-0x007e0000 : "RedBoot config"
0x007e0000-0x00800000 : "boardconfig"
Registered led device: gpio1
Registered led device: gpio2
Registered led device: gpio3
Registered led device: gpio4
Registered led device: wlan
TCP vegas registered
NET: Registered protocol family 17
802.1Q VLAN Support v1.8 Ben Greear
All bugs added by David S. Miller
VFS: Mounted root (squashfs filesystem) readonly.
Freeing unused kernel memory: 120k freed
Please be patient, while OpenWrt loads ...
eth0: Configuring MAC for full duplex
Algorithmics/MIPS FPU Emulator v1.5
- preinit -
Press CTRL-C for failsafe
jffs2 not ready yet; using ramdisk
mini_fo: using base directory: /
mini_fo: using storage directory: /tmp/root
- init -

Please press Enter to activate this console. device eth0 entered promiscuous moebr-lan: port 1(eth0) entering learning state
br-lan: topology change detected, propagating
br-lan: port 1(eth0) entering forwarding state
PPP generic driver version 2.4.2
tun: Universal TUN/TAP device driver, 1.6
tun: (C) 1999-2004 Max Krasnyansky
ip_tables: (C) 2000-2006 Netfilter Core Team
nf_conntrack version 0.5.0 (1024 buckets, 4096 max)
ipt_time loading
wlan: trunk
ath_hal: module license 'Proprietary' taints kernel.
ath_hal: 2008-10-02 (AR5212, AR5312, RF5111, RF5112, RF2316, RF2317, REGOPS_FUN)ath_rate_minstrel: Minstrel automatic rate control algorithm 1.2 (trunk)
ath_rate_minstrel: look around rate set to 10%
ath_rate_minstrel: EWMA rolloff level set to 75%
ath_rate_minstrel: max segment size in the mrr set to 6000 us
wlan: mac acl policy registered
ath_ahb: trunk
Atheros HAL provided by OpenWrt, DD-WRT and MakSat Technologies
wifi0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
wifi0: 11g rates: 1Mbps 2Mbps 5.5Mbps 11Mbps 6Mbps 9Mbps 12Mbps 18Mbps 24Mbps 3swifi0: turboG rates: 6Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps
wifi0: H/W encryption support: WEP AES AES_CCM TKIP
ath_ahb: wifi0: Atheros 2317 WiSoC REV1: mem=0xb0000000, irq=3
jffs2_scan_eraseblock(): End of filesystem marker found at 0x0
jffs2_build_filesystem(): unlocking the mtd device... done.
jffs2_build_filesystem(): erasing all blocks after the end marker... done.
mini_fo: using base directory: /
mini_fo: using storage directory: /jffs

BusyBox v1.11.2 (2009-05-18 13:36:36 CST) built-in shell (ash)
Enter 'help' for a list of built-in commands.

_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
KAMIKAZE (bleeding edge, r91) -------------------
* 10 oz Vodka Shake well with ice and strain
* 10 oz Triple sec mixture into 10 shot glasses.
* 10 oz lime juice Salute!
root@OpenWrt:/# df -h
Filesystem Size Used Available Use% Mounted on
rootfs 2.3M 2.3M 0 100% /
/dev/root 2.3M 2.3M 0 100% /rom
tmpfs 6.7M 60.0k 6.7M 1% /tmp
tmpfs 512.0k 0 512.0k 0% /dev
mini_fo:/tmp/root 2.3M 2.3M 0 100% /tmp/root
/dev/mtdblock3 4.6M 268.0k 4.4M 6% /jffs
mini_fo:/jffs 2.3M 2.3M 0 100% /

A bee's view flying over the Potato landscape

A bee's view flying over the Potato landscape

It even picks up the 8M flash, Ethernet works, and the Wifi drivers come up. In the last installment Linux was choking due to an inaccurate estimate of available memory (32M rather than the actual 16M). I spent an afternoon tracking down the cause – Linux on the AR2317 detects the amount of memory by examining a register that the boot loader sets up before Linux starts. Here is the Linux source (arch/mips/atheros/ar5315/board.c):

memcfg = sysRegRead(AR5315_MEM_CFG);
memsize = 1 + ((memcfg & SDRAM_DATA_WIDTH_M) >> SDRAM_DATA_WIDTH_S);
memsize <<= 1 + ((memcfg & SDRAM_COL_WIDTH_M) >> SDRAM_COL_WIDTH_S);
memsize <<= 1 + ((memcfg & SDRAM_ROW_WIDTH_M) >> SDRAM_ROW_WIDTH_S);
memsize <<= 3; add_memory_region(0, memsize, BOOT_MEM_RAM);

Hmmmm, just after I thought I was free of boot loader issues! Anyway a bit of Googling found another guy in the OpenWRT community who had found and solved exactly the same problem 6 months ago. Thanks Yoonix!

The fix involved changing the SDRAM #defines in the boot loader source and reflashing the boot loader. As soon as we re-flashed the boot loader Linux came up straight away. Joel, a local Linux hacker came around to help out. He wrote a little Python script to model the register configuration changes and make sure I didn't type anything too silly while reflashing the boot loader (my record is not good).

I also found a neat trick for testing Linux kernel images in RedBoot without reflashing:

RedBoot> load openwrt-atheros-vmlinux.elf
RedBoot> go

This can be automated using fconfig -d to make the two steps above the boot script. That way you can compile a new Linux kernel image, then power cycle the Atheros device to test it without flashing anything.

OK, now time to look at bringing up Wifi, or maybe the FXS port. Or maybe I'll just order some pizza!