View source for CM-T3x: Linux: Booting from MMC/SD card

CM-T3530 can boot either from on-board NAND flash or from MMC/SD card. There are certain requirements for MMC/SD card format imposed by internal boot ROM of the OMAP35x processor. The following describes how to create bootable MMC/SD card for different use cases.

== Creating a bootable MMC/SD card ==
In order to create a bootable MMC/SD card compatible with OMAP3x boot ROM, it is necessary to set a special geometry in the partition table. OMAP3x boot ROM can work only with MMC/SD cards that have 255 heads and 63 sectors/track.

=== Linux ===
Detailed description how use Linux {{cmd|fdisk}} utility to adjust MMC/SD card partition table to suit OMAP3x boot ROM requirements can be found at [http://wiki.omap.com/index.php?title=MMC_Boot_Format TI Embedded Processors Wiki].

=== Windows ===
Windows users can use [http://www.sysanalyser.com/sp27213.exe HP USB Disk Storage Format Tool] and follow the steps below:
* Connect the card reader to the Windows machine where the formatting tool has been installed.
* Insert MMC/SD card into the card reader.
* Launch the HP USB Disk Storage Format Tool.
* Select FAT32 as File System.
* Click on Start.
* After formatting is done click OK.

After a bootable MMC/SD card is created it can be used for recovery system startup, for X-Loader and U-Boot testing and for booting Linux entirely from MMC/SD.

== Booting X-Loader and U-Boot ==
* Copy X-Loader to the MMC/SD card's root directory and rename it as {{filename|MLO}}. It is essential that the MLO will be the first file created on the MMC/SD card.
* Copy U-Boot binary to the MMC/SD card's root directory and rename it as {{filename|u-boot.bin}}.
* Insert the MMC/SD card into SB-T35 MMC/SD slot or the CM-T3x on-board micro SD slot.
* Power on the system while holding {{parameter|SD Boot}} (SW1) button on SB-T35.

== Booting Linux ==
CM-T3x can boot Linux from MMC/SD card. The MMC/SD card must have geometry parameters compatible with OMAP3x boot ROM (255 heads, 63 sectors/track) and at least two partitions: FAT32 partition for X-Loader, U-Boot and Linux kernel and ext4 partition for root filesystem.

After MMC/SD card geometry and partition table were updated, create FAT32 filesystem on the first partition and ext4 filsystem on the second partition:
<pre>
sudo mkfs.vfat -F 32 /dev/sdc1
sudo mkfs.ext4 /dev/sdc2
</pre>
In the above example we assumed that the card was recognized as {{filename|/dev/sdc}}.

Mount the MMC/SD card FAT partition and copy X-Loader ({{filename|MLO}}), U-Boot ({{filename|u-boot.bin}}) and Linux kernel ({{filename|uImage}}) to the MMC/SD card:
<pre>
mkdir /mnt/card
mount /dev/sdc1 /mnt/card
cp /path/to/cm-t3x-uboot/images/x-load.bin /mnt/card/MLO
sync
cp /path/to/cm-t3x-uboot/images/u-boot.bin /mnt/card
cp /path/to/cm-t3x-linux/images/uImage-cm-t3x.bin /mnt/card
umount /mnt/card
</pre>

Extract the Linux filesystem into the ext4 partition of the MMC/SD card:
<pre>
mount /dev/sdc2 /mnt/card
cd /mnt/card
tar xjvf /path/to/cm-t3x-linux/images/Angstrom-image.tar.bz2
umount /mnt/card
</pre>

The MMC/SD card is now ready and can be used to boot Linux. The kernel parameters required for MMC/SD boot are

* for Linux kernel v2.6.36 and below:
<pre>
root=/dev/mmcblk0p2 console=ttyS2,115200n8 rootwait mmc_core.removable=0
</pre>

* starting from Linux kernel v2.6.37:
<pre>
root=/dev/mmcblk0p2 console=ttyO2,115200n8 rootwait mmc_core.removable=0
</pre>

== See also ==
[http://code.google.com/p/beagleboard/wiki/LinuxBootDiskFormat BeagleBoard MMC/SD boot]

[[Category:Linux|Booting from MMC/SD card]]
[[Category:U-Boot|Booting from MMC/SD card]]
[[Category:CM-T3530|Linux: Booting from MMC/SD card]]
[[Category:CM-T3517]]
[[Category:CM-T3730]]