[U-Boot] eMMC boot partition booting and SMDK5250 support

[Tom Rini]

On Tue, Jan 28, 2014 at 12:25:02PM -0500, Tom Rini wrote:
> Hey guys,
> 
> I've posted a patch to support the eMMC boot partitions found on the TI
> DRA7xx EVM the other day, and I've been looking at what exactly happens
> with the 'mmc open ...' and 'mmc close ...' commands the
> CONFIG_SUPPORT_EMMC_BOOT enables.  I've got a few questions about how
> exactly the support works on the SMDK5250 and what your platform
> requirements are, so we can re-work the code to be a bit more generic.
> 
> Why do we have it as "open" and "close" ?  Is this because it's a
> version 4.2[1] style device?  I'm working with 4.3-compatible (it's
> actually 4.41, but same method just larger partitions) one and that can
> be done with setting EXT_CSD[179] (BOOT_CONFIG / Boot configuration) _and_
> EXT_CSD[177] to a specific and different value than we've hard-coded
> now.
> 
> I would like to change things to be:
> "mmc open <device>" - Note required for eMMC 4.2 boot method.
> "mmc close <device>" - Same
> "mmc bootpart <device> <partition>" - Used for eMMC 4.3 and later boot
> sequence option 1/2
> "mmc bootbus <device> <value>" - Note used in all boot sequences
> 
> This would make the SMDK5250 sequence be (based on how I think it works
> today):
> mmc dev ...
> mmc open
> mmc write ...
> mmc bootpart ...
> mmc bootbus ...
> mmc close
> 
> And the DRA7xx sequence be:
> mmc dev ...
> mmc write ...
> mmc bootpart ...
> mmc bootbus ...

Oh!  And I forgot the current 'bootpart' which appears to be a resize
operation would become 'bootpart-resize'.

-- 
Tom
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