dataflashboot.bin for AT91SAM9261EK running from a Dataflash Card
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The AT91SAM9261EK has problem which makes it difficult to boot an external Dataflashcard.
If the switches are set to connect the SPI NPCS0 to the Dataflash Card connector, NPCS0
will also be connected to the SPI NPCS3.

If the NPCS3 is enabled a bus conflict will occur.

In order to support booting from Dataflashcard, the NPCS3 must be disabled.
The internal boot rom will disable the NPCS3, but other parts of the boot chain will not.

NPCS3 will also have to be disabled in

* dataflashboot.bin
* U-Boot
* Linux kernel

A boot chain built in this way, will not be able to boot from the internal dataflash and then
access the external dataflash card.

A good approach to enable the use of a single U-boot source is to enable/disable the NPCS3
as a command in U-.boot.

NPCS3	[ on | off ]	 ; 	The default should be "NPCS3 off"
Alternatively, and access to D0000000 will enable the dataflash NPCS3.

The Linux Kernel will also have to be aware of NPCS3.
How is still to be determined.