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Cable modem SPI Flash memory have the following structure:

7 cmdlinepart partitions found on MTD device spansion
partitions[0] = {.name = U-Boot, .offset = 0x00000000,.size = 0x00020000 (128K) }
partitions[1] = {.name = env1, .offset = 0x00020000,.size = 0x00010000 (64K) }
partitions[2] = {.name = env2, .offset = 0x00030000,.size = 0x00010000 (64K) }
partitions[3] = {.name = firmware_101222c, .offset = 0x004a0000,.size = 0x002d0000 (2880K) }
partitions[4] = {.name = nvram, .offset = 0x007b0000,.size = 0x00050000 (320K) }
partitions[5] = {.name = UBFI1, .offset = 0x00040000,.size = 0x003b0000 (3776K) }
partitions[6] = {.name = UBFI2, .offset = 0x003f0000,.size = 0x003b0000 (3776K) }
Creating 7 MTD partitions on "spansion":
0x00000000-0x00020000 : "U-Boot"
0x00020000-0x00030000 : "env1"
0x00030000-0x00040000 : "env2"
0x004a0000-0x00770000 : "firmware_101222c"
0x007b0000-0x00800000 : "nvram"
0x00040000-0x003f0000 : "UBFI1"
0x003f0000-0x007a0000 : "UBFI2"

Bootloader is working, I can connect to modem via serial interface, control boot process and upload firmware. I can't connect admin interface via ip 192.168.100.1, possibly due to wrong configuration stored in nvram. Can I erase Nvram only, without touching other partitions?

?       - alias for 'help'
autoscr - run script from memory
base    - print or set address offset
bdinfo  - print Board Info structure
boot    - boot default, i.e., run 'bootcmd'
bootd   - boot default, i.e., run 'bootcmd'
bootm   - boot application image from memory
bootp   - boot image via network using BootP/TFTP protocol
cmp     - memory compare
coninfo - print console devices and information
cp      - memory copy
crc32   - checksum calculation
echo    - echo args to console
erase   - erase FLASH memory
eval    - return addition/subraction
exit    - exit script
flinfo  - print FLASH memory information
go      - start application at address 'addr'
help    - print online help
iminfo  - print header information for application image
imls    - list all images found in flash
itest   - return true/false on integer compare
loadb   - load binary file over serial line (kermit mode)
loads   - load S-Record file over serial line
loady   - load binary file over serial line (ymodem mode)
loop    - infinite loop on address range
md      - memory display
mm      - memory modify (auto-incrementing)
mtest   - simple RAM test
mw      - memory write (fill)
nm      - memory modify (constant address)
printenv- print environment variables
protect - enable or disable FLASH write protection
rarpboot- boot image via network using RARP/TFTP protocol
reset   - Perform RESET of the CPU
run     - run commands in an environment variable
saveenv - save environment variables to persistent storage
setenv  - set environment variables
sleep   - delay execution for some time
test    - minimal test like /bin/sh
tftpboot- boot image via network using TFTP protocol
version - print monitor version
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You could probably use erase with some arguments to erase only the nvram partition, but I'm not sure if U-Boot can then reinitialize nvram storage. And since nvram usually contains the boot commands, erasing everything could make your unit unbootable. Therefore I would recommend erasing only specific variables.

You can use setenv for that:

To modify the U-Boot environment you have to use the setenv command. When called wih exactly one argument, it will delete any variable of that name from U-Boot's environment, if such a variable exists. Any storage occupied for such a variable will be automatically reclaimed:

INCA-IP # printenv foo
foo=This is an example value.
INCA-IP # setenv foo
INCA-IP # printenv foo
## Error: "foo" not defined
INCA-IP #

Make sure to save the modifications with saveenv.

| improve this answer | |
  • But how I can find a specific variables in nvram which are wrong and cause the web daemon to crash or not start? I don't know which from configuration settings stored in nvram cause problem. – triwo Jul 24 '14 at 20:40
  • How do you even know nvram vars are the problem? U-Boot nvram is mostly used for boot-time config, not OS-level settings. – Igor Skochinsky Jul 24 '14 at 21:01
  • Firmware boots ok, but I can't connect to modem admin interface via 192.168.100.1, can't SSH to it either. Pinging an IP says it unreachable. This happened after I make a change to some settings and rebooted. I just guess this might be due some wrong settings stored in nvram. Since a network connection is not available - can I use U-Boot load files via the serial port? How to do this? I am on Windows. Which protocols to use, kermit or y-modem? Should I rename backup to 'nvram' first? loadb [load address] [baud rate] – triwo Jul 24 '14 at 22:38
  • It's highly unlikely the modem settings are stored in U-Boot's nvram. Try printenv to see the variables you have. – Igor Skochinsky Jul 25 '14 at 14:26
  • Printenv here. There is few superfluous entries (bold text), that were left when I configured firmware upgrade via console port. I'm not sure if this can cause a problem. How to remove them? Normally, the variables should be like this sample. – triwo Jul 25 '14 at 20:03

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