75XX initrd

From Technologic Systems Manuals

After the board is first booted you will be at this shell:

  >> TS-BOOTROM - built Oct 12 2011 13:35:38
  >> Copyright (c) 2009, Technologic Systems
  >> Booting from SD card...
  .
  .
  .
  >> Booted from: SD card                 Booted in: 3.93 seconds
  >> SBC Model number: TS-XXXX            SBC Sub-model number: 0
  >> CPU clock rate: 250MHz               RAM size: 64MB
  >> NAND Flash size: 256MB               NAND Flash Type: 0xdcec (Samsung)
  >> MAC number: 00:D0:69:4F:6F:04        SBC FPGA Version: 7
  >> Temperature Sensor: 37.500 degC      MODE1 bootstrap: ON
  >> RTC present: YES                     Date and Time: Jan  1 1970 00:00:03
  >> MODE2 bootstrap: OFF                 SD card size: 1886MB
  >> Offboard SPI flash type: Micron      Offboard SPI flash size: 8MB
  >> XUARTs detected: 3                   CAN present: NO
  >> Linux kernel version: 2.6.24.4       Linux kernel date: Jun 8 2011
  >> Bootrom date: Oct 12 2011            INITRD date: Dec 27 2011
  >> ts7500ctl date: Jun  8 2011          sdctl date: Jun  8 2011
  >> canctl date: Jun  8 2011             nandctl date: Aug 15 2011
  >> spiflashctl date: Aug 15 2011        xuartctl date: Aug 15 2011
  >> dioctl date: Feb 10 2011             spictl date: Jan 24 2011
  >> dmxctl date: Jun  8 2011             busybox date: Jun 30 2010 (v1.14.2)
  >> ts7500.subr date: Jun 10 2011        daqctl date: Aug 15 2011
  >> linuxrc date: Aug 31 2011            rootfs date: Jan  1 1970
  >> MBR date: Jul 14 2009
  
  Type 'tshelp' for help
  # 
Note: Your version dates may be different depending on ship date and the image used.

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 '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, loads a reloadable FPGA bitstream if one is present, 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. 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 script to always boot into 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 SD or NAND, you would run this:

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

To use any of the other boot scripts, you can simply replace 'linuxrc-sdroot' with the script name mentioned above. Once you have booted to Debian you can return to the initrd by creating the file "fastboot" in root.

touch /fastboot

To automatically boot back to Debian you will need to remove this file.

The small default initrd is only 2Mbyte but there is space for approximately 800 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:

   # /bin/busybox --help
   BusyBox v1.14.2 (2009-08-07 14:43:48 MST) multi-call binary
   Copyright (C) 1998-2008 Erik Andersen, Rob Landley, Denys Vlasenko
   and others. Licensed under GPLv2.
   See source distribution for full notice.
   
   Usage: busybox [function] [arguments]...
      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:
           [, [[, ash, basename, cat, chgrp, chmod, chown, chroot, cmp, cp,
           cpio, cttyhack, cut, date, dd, depmod, devmem, df, dirname, dmesg,
           du, echo, egrep, env, expr, false, fdisk, fgrep, find, grep, gunzip,
           gzip, halt, head, hostname, hush, ifconfig, insmod, kill, killall,
           ln, login, ls, lsmod, md5sum, mdev, mkdir, mknod, modprobe, more,
           mount, msh, mv, netstat, ping, pivot_root, poweroff, printf, ps,
           pwd, reboot, rm, rmdir, rmmod, route, rx, sed, setconsole, setsid,
           sh, sleep, stty, sync, tail, tar, telnetd, test, tftp, top, tr,
           true, udhcpc, umount, unzip, usleep, uudecode, uuencode, vi, wget,
           xargs, yes, zcat

Also on the initrd are the TS specific applications: sdctl, spiflashctl, nandctl, daqctl, ts7500ctl, canctl, and xuartctl. We also provide the ts7500.subr which provides the following functions:

 cvtime()
 usbload()
 sdsave()
 spiflashsave()
 save()
 sd2spiflash()
 spiflash2sd()
 setdiopin()
 getdiopin()
 setrelay()
 setout()
 getin()
 tshelp()
 gettemp()

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 ts7500.subr file with the usbload() function.