Running U-Boot from the SDCard on an Atmel 9G20 is certainly doable. I have recently booted U-Boot and Linux from an SDCard on an Atmel AT91SAM9G45-EKES with no other non-volatile memories and the process is the same with some minor limitations.
The process I used: 1. SAM Boot loader loads "boot.bin" from the first FAT partition 2. Boot.bin loads U-Boot from "uboot.bin" into high DRAM 3. Boot.bin loads a uImage file lower into DRAM 4. Boot.bin jumps into U-Boot 4. U-Boot's boot command boots the image my boot.bin leaves lying around in DRAM. I started with Atmel's SDCard bootstrap example and modified it to load both U-Boot and a Linux image into RAM then jump to U-Boot. The U-Boot and the Linux uImage were "stock" builds with no special features. Once the SD/MMC U-Boot patches make it into the mainline I expect to let U-Boot read the Linux image from the SDCard. The 9G20 has two limitations that I know of: 1. 9G20's boot ROM doesn't support SDHC cards (> 2GB) 2. 9G20's SRAM that boot.bin loads into is 16K which may be too tight for a full FAT handler. The 9G45 has 64K of SRAM so the boot.bin program I used has a full FAT file system handler. Start by looking at the 9G20 "AT91 Software package" at http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4343 and dive into the SD/MMC examples. The SD/MMC patches for AT91 will make this a lot simpler. Enjoy, Bill. > -----Original Message----- > From: u-boot-boun...@lists.denx.de [mailto:u-boot- > boun...@lists.denx.de] On Behalf Of Reinhard Meyer > Sent: Tuesday, September 07, 2010 6:40 PM > To: Will Tucker; u-boot@lists.denx.de > Subject: [U-Boot] Loading u-boot from SD/MMC (was Re: [PATCH v3] AT91: > MCI: add SD/MMC driver using mmc framework) > > 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 > _______________________________________________ > U-Boot mailing list > U-Boot@lists.denx.de > http://lists.denx.de/mailman/listinfo/u-boot _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
