[U-Boot] spl: mmc: use block device number, not hard-coded 0

[Eric Nelson <eric@nelint.com>]

Hi Tom,

On 12/13/2015 06:21 PM, Tom Rini wrote:
> On Sat, Dec 05, 2015 at 12:32:28PM -0700, Eric Nelson wrote:
>
>> In order to support boot from multiple devices through board_boot_order,
>> it's necessary to use the block number of a device.
>>
>> The use of a hard-coded 0 for the device number also creates a need
>> to re-order block devices for use in SPL like this:
>> 	http://git.denx.de/?p=u-boot.git;a=blob;f=board/freescale/mx6slevk/mx6slevk.c;hb=HEAD#l195
> 
> We also do similar'ish things for TI parts (we only register what we're
> booting from).
>
> So, before this can be applied don't we also need a patch for mx6slevk
> and for TI ones too (but that should be "easier" since I think it
> just becomes we always use the normal board_mmc_init) ?

We don't **need** a patch to support existing use cases because the
patch uses the dev number in the block device directly
(mmc->block_dev.dev).

	https://patchwork.ozlabs.org/patch/553026/

I'm not sure about TI boards, but the i.MX6SL EVK code swaps the
non-SPL ordering of mmc devices when compiled for SPL in order
to handle the hard-coded zero:

	http://git.denx.de/?p=u-boot.git;a=blob;f=board/freescale/mx6slevk/mx6slevk.c;hb=HEAD#l195

In other words, "mmc 0" becomes "mmc 1" and vice versa.

The trouble with this approach is that you can't allow for multiple
MMC devices through board_boot_order, because the second will be
device number 1.

Regards,


Eric