====== Installing Linux using U-Boot ======
<WRAP round alert>**Attention**: Use at your own risk! Do not try if no JTAG debugger is available and/or nobody can use it.</WRAP>

===== Linux kernel =====
Start the TQMa35 and then stop the bootloader U-Boot.

<code>
U-Boot 2010.06-00005-gb029844 (May 11 2011 - 15:34:02)

CPU:   Freescale i.MX35 at 532 MHz
Board: TQMa35 [2.0 [RST]
I2C:   ready
DRAM:  256 MiB
Flash: 32 MiB
In:    serial
Out:   serial
Err:   serial
MMC:   FSL_ESDHC: 0, FSL_ESDHC: 1
Net:   FEC0, smc911x-0
Hit any key to stop autoboot:  0
MX35 U-Boot >
</code>

The Linux kernel is downloaded over the network via TFTP. The memory address ''$loadaddr'' is set to ''0x80800000'' by default. There, the kernel is loaded. This address is in the RAM.

<code>MX35 U-Boot > tftp ${loadaddr} uImage_2.6.34.9_tqma35.0101</code>

Now you have to copy the kernel to the flash memory. Before the memory must be erased. The variable ''$kernel_addr'' contains the address of the kernel in the flash, the variable ''$filesize'' contains the size of the file accessed by the last TFTP command. The command ''erase'' erases as much of the flash memory as is required for the new kernel.

<code>MX35 U-Boot > erase ${kernel_addr} +${filesize}</code>

The kernel is copied to the intended location with the command ''cp.b''.

<code>MX35 U-Boot > cp.b ${loadaddr} ${kernel_addr} ${filesize}</code>

The kernel image in the flash can be checked with the command ''imls'':

<code>
MX35 U-Boot > imls
Legacy Image at A0080000:
   Image Name:   Linux-2.6.34.9-00023-gb0fc99a
   Created:      2011-05-04  12:02:23 UTC
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    2194392 Bytes = 2.1 MiB
   Load Address: 80008000
   Entry Point:  80008000
   Verifying Checksum ... OK
</code>

===== RootFS =====
The rootfs is also loaded to ''$loadaddr'' via TFTP.
<code>MX35 U-Boot > tftpboot ${loadaddr} rootfs.jffs2.0008</code>

The flash memory is erased and the rootfs is written to address ''$ramdisk_addr''.
<code>
MX35 U-Boot > erase
MX35 U-Boot > cp.b ${loadaddr} ${ramdisk_addr} ${filesize}
</code>

The appropriate MTD parameters have to be passed to the Linux kernel. These are saved in an U-Boot environment variable.
<code>
MX35 U-Boot > setenv mtdparts 'mtdparts=physmap-flash.0:256k(u-boot),256k(env),2560k(kernel),29M(jffs2),-(user)'
MX35 U-Boot > setenv jffsargs ${jffsargs} ${mtdparts}
MX35 U-Boot > saveenv
</code>

Now the boot method ''flash_jffs'' can be set as the standard boot method:
<code>
MX35 U-Boot > setenv bootcmd ${flash_jffs}
MX35 U-Boot > saveenv
</code>

===== Sources =====
  * http://www.denx.de/wiki/DULG/Manual