[U-Boot] [PATCH 2/6] add header with a generic set of boot commands defined.

[Stephen Warren <swarren@wwwdotorg.org>]

On 03/21/2014 12:48 PM, Tom Rini wrote:
> On Thu, Mar 20, 2014 at 05:12:57PM -0500, Dennis Gilmore wrote:
> 
>> As the next step in a generic config we are introducing a set of generic boot
>> paramaters. Depending on the hardwares configuration, booting from supported
>> hardware will be enabled, mmc, usb, sata, scsi, ide, pxe and dhcp.
>>
>> There is nothing to stop this being extended to support nand and any other
>> type of storage that comes along. An ideal future enhancement will be to
>> allow the user to dynamically reorder the boot devices, and allow one off
>> boots. for example simply be able to pxe boot to reinstall
> [snip]
>> +	"bootcmd_mmc0=setenv devnum 0; run mmc_boot;\0" \
>> +	"bootcmd_mmc1=setenv devnum 1; run mmc_boot;\0"
>> +#define BOOT_TARGETS_MMC "mmc1 mmc0"
> 
> This is because we want to prefer eMMC to SD card?  Or is mmc1=SD,
> mmc0=eMMC on Tegra?  That's opposite of TI parts so we might need to
> #ifndef/define/endif that combo at least.

On most (all?) Tegra devices, mmc1 is SD and mmc0 is eMMC. We prefer to
try to boot from SD first so that the user can just plug in an SD card
to boot from it if they want, but otherwise boot from eMMC (just like
floppy vs HDD on a PC) without having to muck with boot order manually.

Well, that and I almost exclusively boot from SD, so it's marginally
faster and less noisy:-)