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Imximage Boot Image generation using mkimage
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This document describes how to set up a U-Boot image
that can be booted by Freescale MX25, MX35 and MX51
processors via internal boot mode.

These processors can boot directly from NAND, SPI flash and SD card flash
using its internal boot ROM support. They can boot from an internal
UART, if booting from device media fails.
Booting from NOR flash does not require to use this image type.

For more details refer Chapter 2 - System Boot and section 2.14
(flash header description) of the processor's manual.

This implementation does not use at the moment the secure boot feature
of the processor. The image is generated disabling all security fields.

Command syntax:
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./tools/mkimage -l <mx u-boot_file>
		to list the imx image file details

./tools/mkimage -T imximage \
		-n <board specific configuration file> \
		-e <execution address> -d <u-boot binary>  <output image file>

For example, for the mx51evk board:
./tools/mkimage -n ./board/freescale/mx51evk/imximage.cfg \
		-T imximage -e 0x97800000  \
		-d u-boot.bin u-boot.imx

You can generate directly the image when you compile u-boot with:

$ make u-boot.imx

The output image can be flashed on the board SPI flash or on a SD card.
In both cases, you have to copy the image at the offset required for the
chosen media devices (0x400 for both SPI flash or SD card).

Please check Freescale documentation for further details.

Board specific configuration file specifications:
-------------------------------------------------
1. This file must present in the $(BOARDDIR) and the name should be
	imximage.cfg (since this is used in Makefile).
2. This file can have empty lines and lines starting with "#" as first
	character to put comments.
3. This file can have configuration command lines as mentioned below,
	any other information in this file is treated as invalid.

Configuration command line syntax:
---------------------------------
1. Each command line is must have two strings, first one command or address
	and second one data string
2. Following are the valid command strings and associated data strings:-
	Command string		data string
	--------------		-----------
	BOOT_FROM		nand/spi/sd/onenand
				Example:
				BOOT_FROM spi
	DATA			type address value

				type: word=4, halfword=2, byte=1
				address: physycal register address
				value: value to be set in register
				All values are in in hexadecimal.
				Example (write to IOMUXC):
				DATA 4 0x73FA88a0 0x200

The processor support up to 60 register programming commands. An error
is generated if more commands are found in the configuration file.

3. All commands are optional to program.

Setup a SD Card for booting
--------------------------------

The following example prepare a SD card with u-boot and a FAT partition
to be used to stored the kernel to be booted.
I will set the SD in the most compatible mode, setting it with
255 heads and 63 sectors, as suggested from several documentation and
howto on line (I took as reference the preparation of a SD Card for the
Beagleboard, running u-boot as bootloader).

You should start clearing the partitions table on the SD card. Because
the u-boot image must be stored at the offset 0x400, it must be assured
that there is no partition at that address. A new SD card is already
formatted with FAT filesystem and the partition starts from the first
cylinder, so we need to change it.

You can do all steps with fdisk. If the device for the SD card is
/dev/mmcblk0, the following commands make the job:

1. Start the fdisk utility (as superuser)
	fdisk /dev/mmcblk0

2. Clear the actual partition

Command (m for help): o

3. Print card info:

Command (m for help): p
Disk /dev/mmcblk0: 1981 MB, 1981284352 bytes

In my case, I have a 2 GB card. I need the size to set later the correct value
for the cylinders.

4. Go to expert mode:

Command (m for help): x

5. Set card geometry

Expert command (m for help): h
Number of heads (1-256, default 4): 255

Expert command (m for help): s
Number of sectors (1-63, default 16): 63
Warning: setting sector offset for DOS compatiblity

We have set 255 heads, 63 sector. We have to set the cylinder.
The value to be set can be calculated with:

	cilynder = <total size> / <heads> / <sectors> / <blocksize>

in this example,
	1981284352 / 255 / 63 / 512 = 239.x = 239


Expert command (m for help): c
Number of cylinders (1-1048576, default 60032): 239

6. Leave the expert mode
Expert command (m for help): r

7. Set up a partition

Now set a partition table to store the kernel or whatever you want. Of course,
you can set additional partitions to store rootfs, data, etc.
In my example I want to set a single partition. I must take care
to not overwrite the space where I will put u-boot.

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-239, default 1): 3
Last cylinder, +cylinders or +size{K,M,G} (3-239, default 239): +100M

Command (m for help): p

Disk /dev/mmcblk0: 1967 MB, 1967128576 bytes
255 heads, 63 sectors/track, 239 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xb712a870

        Device Boot      Start         End      Blocks   Id  System
/dev/mmcblk0p1               3          16      112455   83  Linux

I have set 100MB, leaving the first 2 sectors free. I will copy u-boot
there.

8. Write the partition table and exit.

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

9. Copy u-boot.imx on the SD card

I use dd:

dd if=u-boot.imx of=/dev/mmcblk0 bs=512 seek=2

This command copies the u-boot image at the address 0x400, as required
by the processor.

Now remove your card from the PC and go to the target. If evrything went right,
the u-boot prompt should come after power on.

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Author: Stefano babic <sbabic@denx.de>