Kernel Flashing supplement

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Upgrading a Kernel via Handylink Serial Connection (requires serial to handylink)

Overview

The BUG stores the GNU/Linux kernel in onboard flash memory. The remainder of the user root-filesystem exists on the MMC or SD card provided with the BUG. BUG uses Redboot as the boot manager. To upgrade your kernel in the case of boot failure, the steps below outline how to flash the kernel via a custom serial/handylink cable. For more information about this cable see Handylink to DB9, or contact BUG+Care. It is very important that the instructions below are followed exactly. If you accidentally overwrite Redboot, for example, the only solution is to use a BDI and JTAG to reimage the flash component on the board. This is a very time-consuming process and is typically only done that the factory if necessary.

Requirements

  • You need minicom (or kermit) and lrzsz on host system. 
sudo apt-get install lrzsz minicom

Delete the old Kernel (if necessary)

  • Boot the BUG and ctrl-c to drop into Redboot 
Running boot script in 1.000 seconds - enter ^C to abort
^C (ctl-c)
  • List the flash partition table to determine the kernel name: fis list 
BUG_RedBoot> fis list 
Name              FLASH addr  Mem addr    Length      Entry point
RedBoot           0xA0000000  0xA0000000  0x00040000  0x00000000
kernel            0xA1000000  0x00100000  0x00210000  0x00100000
FIS directory     0xA1FFC000  0xA1FFC000  0x00003000  0x00000000
RedBoot config    0xA1FFF000  0xA1FFF000  0x00001000  0x00000000



BUG_RedBoot> fis delete kernel
Delete image 'kernel' - continue (y/n)? y
flash_erase(): addr = a0100000, len = 200000
flash_erase(): end_addr = a0300000, block = a0100000
flash_erase(): end_addr = a0300000, block = a0100000
... Erase from 0xa0100000-0xa0300000: flash_erase(): block = a0100000, block_size = 4000


Send the Kernel

  • Tell Redboot to expect a kernel via ymodem and load it ram: load -b 0x100000 -m ymodem -v -r 
BUG_RedBoot> load -b 0x100000 -m ymodem -v -r
CC...
  • Send the Kernel via ymodem in minicom, the key-combination to do this is Ctrl+A then Z, then S, then navigate to the zImage file you downloaded above using the arrow keys and spacebar to get in a folder , tag the file (space) and hit Enter for Okay. You'll see progress in the line Ymodem sectors/kbytes sent, and final output should look like this: 
+-----------[ymodem upload - Press CTRL-C to quit]------------+
|Retry 0: NAK on sector                                       |
|Bytes Sent:1621120   BPS:7560                                |
|Sending:                                                     |
|Ymodem sectors/kbytes sent:   0/ 0k                          |
|Transfer complete                                            |
|                                                             |
| READY: press any key to continue...                         |
+-------------------------------------------------------------+



CRaw file loaded 0x00100000-0x0028bc27, assumed entry at 0x00100000
xyzModem - CRC mode, 12667(SOH)/0(STX)/0(CAN) packets, 6 retries

Write Kernel to Flash

  • After loading the kernel into memory, you'll need to write it to flash. See below.
  • List the flash partition table: fis list 
BUG_RedBoot> fis list 
Name              FLASH addr  Mem addr    Length      Entry point
RedBoot           0xA0000000  0xA0000000  0x00040000  0x00000000
FIS directory     0xA1FFC000  0xA1FFC000  0x00003000  0x00000000
RedBoot config    0xA1FFF000  0xA1FFF000  0x00001000  0x00000000

BUG_RedBoot> fis unlock -f 0xa0100000 -l 0x200000  

BUG_RedBoot> fis create -b 0x100000 -l 0x200000 -f 0xa0100000 kernel 
...

Configure Boot Script

  • You will want to ensure that Redboot is configured to load your kernel image. Use fconfig to see the boot script. Type fconfig, hit enter, hit enter when asked Run script at boot: true, hit enter again. 
BUG_RedBoot> fconfig
Run script at boot: true
Boot script:
.. clock 532
.. fis load kernel -b 0x100000
.. exec -b 0x100000 -l 0x200000 -c "noinitrd console=ttymxc4,115200 rootdelay=1 init=/linuxrc root=/dev/mmcblk0p1 ip=192.168.0.111:192.168.0.121:192.168.0.121:255.255.255.0:BUG::off mem=128M jtag=on"
Enter script, terminate with empty line
>>
  • In this case, the boot script is configured to load the kernel image called kernel into memory address 0x100000, as determined by the second line. If yours says "image2" or something else, you'll want to enter: 
>> clock 532
>> fis load kernel -b 0x100000
>> exec -b 0x100000 -l 0x200000 -c "noinitrd console=ttymxc4,115200 rootdelay=1 init=/linuxrc root=/dev/mmcblk0p1 ip=192.168.0.111:192.168.0.121:192.168.0.121:255.255.255.0:BUG::off mem=128M jtag=on"
  • Hit enter twice to indicate the end of the boot script. There is output to further configure the boot process. You'll want to keep these the same by hitting enter at each but the very last Update RedBoot non-volatile configuration - continue (y/n)? y. The default is n, or no, and the changes will not be saved unless you respond y, for yes. 
>>
Boot script timeout (1000ms resolution): 1
Use BOOTP for network configuration: false
Gateway IP address: 192.169.0.1
Local IP address: 192.169.0.2
Local IP address mask: 255.255.255.0
Default server IP address: 192.169.0.1
Board specifics: 0
Console baud rate: 115200
Set eth0 network hardware address [MAC]: true
eth0 network hardware address [MAC]: 0x00:0x50:0xC2:0x69:0xC0:0x18
GDB connection port: 9000
Force console for special debug messages: false
Network debug at boot time: false
Update RedBoot non-volatile configuration - continue (y/n)? y
  • Reset the BUG to test your changes. 
BUG_RedBoot>reset
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