TS-4200 initrd

From Technologic Systems Manuals

When the board first boots you should see output similar to this:

 >> TS-BOOTROM - built Mar  9 2011 09:59:23
 >> Copyright (c) 2011, Technologic Systems
 >> Booting from SD card...
 .
 .
 .
 Uncompressing Linux... done, booting the kernel.
 >> Booted from: SD card                 Booted in: 1.40 seconds
 >> SBC Model number: TS-4200            SBC Sub-model number: 0
 >> CPU clock rate: 396 MHz              RAM size: 128MB
 >> NAND Flash size: 256MB               NAND Flash Type: 0xdc20 (STMicro)
 >> MAC number: 00:D0:69:44:3E:9B        SBC FPGA Version: 4
 >> Temperature Sensor: 31.500 degC      MODE1 bootstrap: OFF
 >> RTC present: YES                     Date and Time: Jan  1 2001 00:01:49
 >> Base board type: TS-8200/Unknown     Base board FPGA Version: not present
 >> MODE2 bootstrap: ON                  SD card size: 1886MB
 >> Offboard SPI flash type: not present Offboard SPI flash size: not present
 >> XUARTs detected: 0                   CAN present: NO
 >> Linux kernel version: 2.6.36.2       Linux kernel date: Oct 7 2011
 >> Bootrom date: unknown                INITRD date: Oct  7 2011
 >> ts4200ctl date: Sep 27 2011          sdctl date: not present
 >> canctl date: not present             nandctl date: Sep 26 2011
 >> spiflashctl date: not present        xuartctl date: not present
 >> dioctl date: not present             spictl date: not present
 >> dmxctl date: not present             busybox date: Sep 26 2011 (v1.18.3)
 >> ts4200.subr date: Sep 29 2011        daqctl date: not present
 >> linuxrc date: Sep 27 2011            rootfs date: Oct  7 2011
 >> MBR date: Sept 20 2011
 
 Type 'tshelp' for help
 # 

This is a busybox shell which presents you with a very minimalistic system. This filesystem is loaded into memory, so none of the changes will be saved unless you type the command

save

or mount a filesystem as read/write. This can also provide a simple mechanism for running your application in an entirely read-only environment. The linuxrc script will be the first thing executed as soon as the kernel is loaded. This sets the default IP address, starts the userspace ctl applications, and more. Read the linuxrc for more information.

While busybox itself doesn't contain much functionality, it does mount the Debian partition under /mnt/root/. It will also add common paths and load libraries from the Debian system. Many of the Debian applications will work by default. Whether or not a Debian application will work in fastboot needs to be judged per application. If an application relies on certain paths being in certain places, or running services, you should instead boot to Debian to run them.

This shell when started on the COM port is what is blocking a Debian boot. If you close it by typing

exit

the boot process will continue. If you are connected through telnet, this will instead open up its own instance of the shell so typing

exit

will only end that session. Through any connection method you can relink the linuxrc to change it to boot by default to Debian.

The initrd has these boot scripts available:

Script Function
linuxrc-fastboot (default) Boots immediately to a shell in ramdisk. This will mount whichever boot medium you have selected to /mnt/root/. When you type 'exit', it will boot to that medium.
linuxrc-nandmount Same as the linuxrc-fastboot script, but will mount and boot the debian partition from NAND.
linuxrc-sdmount Same as the linuxrc-fastboot script, but will mount and boot the debian partition from SD.
linuxrc-sdroot Boots immediately to the Debian stored on either SD or NAND depending on which device you have currently selected.
linuxrc-sdroot-readonly Same as linuxrc-sdroot, except it will mount the Debian partition read only while creating a unionfs with a ramdisk. Changes will only happen in memory and not on disk.
linuxrc-usbroot Mounts the first partition of the first detected USB mass storage device and boots there.
Note: Keep in mind the boot medium is selected by the pinout on your baseboard, not through software.

For example, to set the linuxrc to boot immediately to Debian on the SD you would run this:

rm linuxrc; ln -s /linuxrc-sdroot /linuxrc; save

The small default initrd is only 2Mbyte but there is space for approximately 300 Kbyte of additional user applications. The binaries on the initrd are dynamically linked against embedded Linux's "uclibc" library instead of the more common Linux C library "glibc". "uclibc" is a smaller version of the standard C library optimized for embedded systems and requires a different set of GCC compiler tools which are available here.

The compiled instance of busybox includes several internal commands listed below:

 BusyBox v1.18.3 (2011-09-22 17:52:49 MST) multi-call binary.
 Copyright (C) 1998-2009 Erik Andersen, Rob Landley, Denys Vlasenko
 and others. Licensed under GPLv2.
 See source distribution for full notice.
 
 Usage: busybox [function] [arguments]...
    or: busybox --list[-full]
    or: function [arguments]...
 
 	BusyBox is a multi-call binary that combines many common Unix
 	utilities into a single executable.  Most people will create a
 	link to busybox for each function they wish to use and BusyBox
 	will act like whatever it was invoked as.
 
 Currently defined functions:
 	[, [[, ar, ash, basename, cat, chat, chgrp, chmod, chown, chroot, chrt,
 	cmp, cp, cpio, cttyhack, cut, date, dc, dd, depmod, devmem, df,
 	dirname, dmesg, dnsdomainname, du, echo, egrep, env, expr, false,
 	fdisk, fgrep, find, free, grep, gunzip, gzip, halt, head, hostname,
 	hush, hwclock, ifconfig, insmod, ipcrm, ipcs, kill, killall, ln, login,
 	ls, lsmod, lsusb, md5sum, mdev, microcom, mkdir, mkfifo, mknod,
 	modinfo, modprobe, more, mount, mv, netstat, nohup, ping, pivot_root,
 	poweroff, printf, ps, pwd, rdate, reboot, rm, rmdir, rmmod, route, rx,
 	sed, seq, setconsole, setsid, sh, sha1sum, sha256sum, sha512sum, sleep,
 	stty, sync, sysctl, tail, tar, tee, telnetd, test, tftp, time, top,
 	touch, tr, true, udhcpc, umount, uname, unxz, unzip, uptime, usleep,
 	uudecode, uuencode, vi, watch, wget, xargs, xz, xzcat, yes, zcat


Also on the initrd are the TS specific applications: nandctl and ts4200ctl. We also provide the ts4200.subr which provides the following functions:

 eth_off()
 eth_on()
 attime()
 usb_off()
 usb_on()
 usbload()
 sdload()
 nandsave()
 sdsave()
 save()
 sd2nand()
 nand2sd()
 setdiopin()
 getdiopin()
 getadc()
 pc104on()
 pc104off()
 setupclk()
 tshelp()

By default, linuxrc will not insert the necessary modules into the kernel to mount and use USB devices within the initrd/busybox environment if there is no USB device present upon bootup (USB support is enabled by default within the Debian environment). The quickest way to get a USB device (like a USB thumb drive) to mount in the initrd/busybox environment is to ensure that it is plugged in before the SBC is powered up. In order to get hot-swappable USB devices regardless of device presence at bootup time, you must "modprobe" the necessary modules. This has been done for you in the ts4200.subr file with the usbload() function.