zedboard: Update readme.txt to reflect BOOT.BIN generation

Zedboard information including schematics, reference designs, and manuals are

available from http://www.zedboard.org .

The U-Boot firmware for the Xilinx Zynq All Programmable SoC depends

on some proprietary code. This dependency consists of a pair of

files are available from the Xilinx SDK installation.

Steps to create a working system for Zedboard:

You will need these files from Xilinx SDK installation to generate

the U-Boot firmware:

	ps7_init.c

	ps7_init.h

1) make zedboard_defconfig

2) make

3) copy files BOOT.BIN, u-boot-dtb.img, rootfs.cpio.uboot,

	uImage, zynq-zed.dtb into your SD card

4) boot your Zedboard

Buildroot will create the following files and place them in the

<output>/images directory.

	zynq-zed.dtb

	rootfs.cpio.uboot

	uImage

	u-boot.img

	boot.bin

The expected output:

 U-Boot SPL 2015.07-rc2 (Jun 18 2015 - 16:42:58)

 mmc boot

 reading system.dtb

 spl_load_image_fat_os: error reading image system.dtb, err - -1

 reading u-boot-dtb.img

 reading u-boot-dtb.img

uboot.bin  -- U-Boot SPL w/ Xilinx boot.bin wrapper

---------------------------------------------------

 U-Boot 2015.07-rc2 (Jun 18 2015 - 16:42:58 +0200)

Due to licensing issues, the files ps7_init.c/h are not able to be

distributed with the U-Boot source code.  These files are required to make a

boot.bin file.

If you already have the Xilinx tools installed, the following sequence will

unpack, patch and build the rfs, kernel, uboot, and uboot-spl.

make zedboard_defconfig

make uboot-patch

cp ${XILINX}/ISE_DS/EDK/sw/lib/hwplatform_templates/zed_hw_platform/ps7_init.{c,h} \

output/build/uboot-xilinx-v2014.1/board/xilinx/zynq/

After copying these files into the U-Boot source tree, you can

continue the build with:

make

*Notice*

While the build will successfully complete without the ps7_init.*

files,  the uboot.bin file generated by this configuration will not

function properly on the Zedboard.  Therefore, it is imperative that

the ps7_init.* files be copied into the U-Boot source tree any time

the clean, or uboot-dirclean targets are made.

 Model: Zynq ZED Board

 I2C:   ready

 DRAM:  ECC disabled 512 MiB

 MMC:   zynq_sdhci: 0

 Using default environment

 ...

When using an older U-Boot then 2015.07, a working ps7_init.c

file is required to be installed into the U-Boot directory

structure. From 2015.07, the major Zynq-based boards are

supported without any manual intervention.

Resulting system

----------------

A FAT32 partition should be created at the beginning of the SD Card

and the following files should be installed:

	/boot.bin

	/devicetree.dtb

	/BOOT.BIN

	/zynq-zed.dtb

	/uImage

	/uramdisk.image.gz

	/u-boot.img

	/rootfs-cpio.uboot

	/u-boot-dtb.img

All needed files can be taken from output/images/

boot.bin, uImage and u-boot.img are direct copies of the same files

BOOT.BIN, uImage and u-boot-dtb.img are direct copies of the same files

available on output/images/

devicetree.dtb is just zynq-zed.dtb renamed.

There is a patch attached that redefines the U-Boot's environment

to work with Buildroot out-of-the-box.

You can alter the booting procedure by creating a file uEnv.txt

in the root of the SD card. It is a plain text file in format

<key>=<value> one per line:

uramdisk.image.gz is rootfs.cpio.uboot renamed

kernel_image=myimage

modeboot=myboot

myboot=...