[U-Boot-Users] AT91 Bootstrap in U-boot

[Ulf Samuelsson]

> Hi,
> Is their a reason why the AT91 Bootstrap code was never ported to
> U-boot?

Yes, Integrating AT91Bootstrap only makes sense if you have a parallel flash.

There are no Atmel AT91SAM9 dev boards which uses a parallel flash.
The AT91RM9200 boards uses parallel flash, but they do not use AT91Bootstrap.

The SAM9 boards all have an AT45 dataflash which has an SPI interface.
The BMS pin needs to be configured to make the CPU boot from the internal BootROM.
The BootROM copies the initial application at address 0 of the dataflash to internal SRAM.
The SRAM can be as small as 4 kB (in the AT91SAM9260) and that limits the functionality.
U-Boot does not fit, so you have AT91bootstrap.

AT91bootstrap needs to run BEFORE U-Boot is started.


Best Regards
Ulf Samuelsson