[U-Boot] accessing eMMC boot partitions from U-Boot

[Sergey Kubushyn]

On Mon, 13 Mar 2017, Stephen Warren wrote:

> On 03/13/2017 03:34 PM, Tim Harvey wrote:
>>  Greetings,
>>
>>  I'm working with some boards with eMMC FLASH and understand that I can
>>  set the fields of the PARTITION_CONFIG with the 'mmc partconf' command
>>  to specify what partition is used for boot. Once I do that to set the
>>  boot0 partition for example, how can I access that  partition from
>>  within u-boot via mmc read/write? In Linux the kernel provides access
>>  to user/boot0/boot1/rpmb via different devices, but I don't see u-boot
>>  doing that.
>
> The "mmc dev" command can be used to select which MMC device to operate on. 
> The "typical" command "mmc dev 0" selects the main partition on MMC device 0 
> for later MMC-specific commands such as "mmc read". You can add an extra 
> parameter to that command to request a specific HW partition, e.g. "mmc dev 0 
> 1" selects boo0 of MMC device 0 and "mmc dev 0 2" selects boot1.
>
> A similar naming scheme exists for commands that take a complete device 
> specification each time. For example, "part list mmc 0" to list partitions in 
> the main partition on MMC device 0, or "part list mmc 0.1" to list partitions 
> on boot0 of MMC device 0.

Unfortunately this has absolutely nothing to do with eMMC _BOOT_
partitions... There 2 of those on eMMC and they are _NOT_ accessible in
this fashion. Neither they bear any FS on them. eMMC is _SPECIAL_ in that
respect -- although it does look like e.g. SD Card it has 2 additional
_HARDWARE_ boot partitions that none of other MMC devices have. Those are
invisible and they are _NOT_ a part of user partition.

I did try to push a patch that would've allowed to put U-Boot environment
into boot partitions so entire _USER_ partition would be free but
unfortunately it had been met with fierce resistance, as usual, as well as
my patch for writing a bootable U-Boot into boot NAND on iMX6. I will
probably make another attempt tomorrow or later this week as time permitted
against 2017-03 but will give up if this one also failed...

We do use U-Boot with those patches in production devices which we
manufacture many thousands of with no problems at all.

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