[U-Boot] SAMA5D2 xplained SD/eMMC boot

[James Chargin]

On 04/18/2016 09:54 AM, Andreas Bießmann wrote:
> Hi Marek,
>
> On 2016-04-18 17:30, Marek Vasut wrote:
>> Hi!
>>
>> I've been playing around with latest mainline u-boot on sama5d2 xplained
>> ultra. I noticed that if I want to boot the board from
>> SD card (SDHCI1), the board will indeed load the SPL from it, but
>> SPL will try to load u-boot.img from eMMC (SDHCI0) and fail, as
>> my eMMC is blank. This is a result of hard-coding boot device to
>> BOOT_DEVICE_MMC1 in arch/arm/mach-at91/spl.c spl_boot_device() I
>> think.
>>
>> Is there any way to discern from which SDHCI the board booted to
>> continue loading u-boot.img from the correct one ? This would let
>> us implement board_boot_order() and boot from correct SDHCI.
>
> AFIAK it is not possible to detect the boot medium in a running device.
> At least was this the case when I checked it the last time (for sama5d3).

For the TI am5728 (ARM V7), there is a register, CTRL_CORE_BOOTSTRAP 
(0x4A0026C4) which contains the boot device selection at last power 
cycle. I'm new to ARM so I don't know how likely it is that the Atmel 
part has a similar register. Good luck.

-- 
Jim Chargin
AJA Video Systems                       jimc at aja.com
(530) 271-3334                          http://www.aja.com