[U-Boot] Loading u-boot from SD/MMC (was Re: [PATCH v3] AT91: MCI: add SD/MMC driver using mmc framework)

[Reinhard Meyer]

Dear Will Tucker,
 > Hi,
 >
 > I’m trying to get the ATSAM9G20-EK booting from SD/MMC on MCI A, with the Nand
 > and Dataflash disabled, with no luck.
 >
 > I have gotten the latest u-boot-atmel compiled and placed boot.bin on a FAT 16
 > formatted. When I turn power on I only get RomBoot on the debug uart.
 >
 > 1) Do I need to use the latest AT91Bootstrap, I have v1.16 but do not see any
 > way to enable the mci
 >
 > If I need an update where can I get the latest version?
 >
 > Any help would be appreciated,
 >
 > Will Tucker
 >

First, please observe the following:
1. Start a new thread for comments/questions unrelated to the existing thread.
2. Always post the u-boot mailing list as well.
3. Please make your lines wrap at less than 80 characters.

To give a brief answer to your issue:

Please study sections 8 and 13 of the 9G20 datasheet. As a result you will see
that the ROM will try to load "boot.bin" to internal SRAM. This will limit the
image size to 16K. Apparently that cannot be u-boot itself. This 16k code would
need to initialize SDRAM and load another, larger file (e.g. u-boot.bin) from
SD/MMC into SDRAM. I don't know whether AT91Bootstrap sources already handle
such a situation. Latest Versions you will find on the Atmel Website.

Please note that this is not an u-boot issue.

The patch "SD/MMC support" for u-boot enables to access SD/MMC from u-boot ONCE
it is running.

Best Regards,
Reinhard