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

[Minkyu Kang]

Jaehoon,
How you think?

On 29/01/14 04:31, Tom Rini wrote:
> 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'.
>