[Arm-netbook] Booting from SD card with switch on so-dimm in other direction ...

[Luke Kenneth Casson Leighton]

On Wed, Mar 24, 2010 at 2:39 PM, Jonathan Ervine <jon.ervine at gmail.com> wrote:

> Moving the switch on my SO-DIMM leaves the netbook unbootable, regardless of whether the SD card is inserted. Pressing the power switch just flashes the light briefly.

 ok  - i've been thinking about that: 2gb NAND flash drive sizes
(cyls, sectors) are _different_ from SD card 2gb sizes.

 so the trick of copying 2gb NAND to 2gb SD using dd isn't necessarily
guaranteed to work.

 only by getting u-boot at exactly the right point from the _end_ of
the SD card will it be executed.

 sooOoo.... could you check, jon, the message i sent earlier, confirm
that the SD card cyls/sectors and size are identical to what i saw
under fdisk, then copy that mmcblk0p1 using the dd command which skips
to the end of the SD card?

 ... actually, let me correc those instructions, here, because i got
them rather wrong (mmblk0p1.bz2 not mmcblk0p1.bz2 etc.)



you MUST use a 2gb SDcard for this to work, so if you use fdisk, it
must show the same params as here:

# fdisk /dev/mmcblk0

Command (m for help): p

Disk /dev/mmcblk0: 1977 MB, 1977614336 bytes
61 heads, 62 sectors/track, 1021 cylinders
Units = cylinders of 3782 * 512 = 1936384 bytes


if you have exactly that, then the following will work.

# wget http://lkcl.net/arm_systems/CT-PC89E/mmcblk0p1.bz2
# bunzip2 mmcblk0p1.bz2
# dd if=mmcblk0p1 of=/dev/mmcblk0 seek=3672000 bs=512


if you know what you're doing, you should be able to adapt that
accordingly: subtract or add the appropriate number of 512-byte
sectors onto the "seek=" parameter, depending on this formula:

 seek = 3672000 + ( ( {your-drive-size-in-bytes}-1977614336 ) / 512 )

i repeat because there seems to be some confusion about what's needed:
formatting of the SD card IS NOT REQUIRED AND WILL MAKE ABSOLUTELY NO
DIFFERENCE.  this is _direct_ copy and the ARM cpu uses _direct_
reading, bypassing any need or requirement for any kind of
"formatting" of any kind.

also to recap: frans has suggested making modifications to the
partition (which can be done safely) in particular making
modifications to the u-boot parameters.  this is a good idea.

l.