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Boot from uSD Card...

Questions and discussions related to Inforce 6540

by Inforce » Wed Jul 01, 2015 7:51 am

I agree that there's no real reason to muck with those partitions on purpose, but it would be nice to know that if I did accidentally screw it up, I could recover without losing a week or two of development time returning the board. My basic problem is my rootfs is likely to exceed 2G (I thought the board shipped with 4G).
The board appears to be equipped with 2G (rather than the advertised 4G). The part number of the eMMC is "SDIN8DE2-16G". I couldn't find a datasheet for that exact part number, but since the output of "df -h /" is:
Filesystem Size Used Avail Use% Mounted on
/dev/mmcblk0p25 2.0G 1.6G 387M 81% /
I then assume that the "16G" in the part number implies bits; meaning 2G bytes.
I am likely to need to install packages that will cause this 2G to overflow during development. I was hoping to just boot off uSD to support a larger rootfs. If I can't do that, then I need an alternative. Here were some of my thoughts:
1. change the kernel command line to use "rootfs=/dev/mmcblk1xxx"
2. use FS overlay to just expand rootfs to the uSD card (don't know much about this yet)
3. remount things somehow at startup…
To experiment here, I am more likely to accidentally screw up the partitions.
See my problem? Any thoughts?
Thanks,
Ed
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by Inforce » Wed Jul 01, 2015 7:52 am

Hi Ed,
Boot from SD card is not supported on APQ8084 based platforms. You *can* brick the board but there is no reason for you to erase the boot partitions.

Cheers,
Sundeep
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by Inforce » Wed Jul 01, 2015 7:52 am

Hi,
Text in the IFC6540_Ubuntu_Linux_ReleaseNotes_002337_Rev_A.pdf from Inforce (dated Jan 12, 2015) says that booting from the SD card is currently not supported. That was 3 months ago. Is there any update on this?
It scares me to think I can "brick" this board and the only way to fix it is to send it back and lose a week (give or take) of development time.
Ed
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by kekiefer » Tue Jul 21, 2015 10:06 am

Ed,

You can at least change the kernel command line to load the rootfs from the SD card. The following worked for me; SD card formatted with a single ext4 partition:

Code: Select all
sudo abootimg -u boot_ifc6540_v1.1.img -c "cmdline=console=tty0 console=ttyHSL0,115200,n8 root=/dev/mmcblk1p1 rootwait rw"
sudo fastboot flash boot boot_ifc654v1.1.img


To restore the original boot arguments:

Code: Select all
sudo abootimg -u boot_ifc6540_v1.1.img -c "cmdline=console=tty0 console=ttyHSL0,115200,n8 root=/dev/mmcblk0p25 rootwait rw"
sudo fastboot flash boot boot_ifc654v1.1.img


Still, I would also like to know more about the apparent lack of full SD card boot support, since the hardware documents do say it is possible, and it is apparently possible on the 64xx boards (to recover a bricked unit). What's different between the two platforms here?

Kurt
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