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

[Sergey Kubushyn]

On Mon, 13 Mar 2017, Stephen Warren wrote:

> On 03/13/2017 07:08 PM, Sergey Kubushyn wrote:
>>  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...
>
> That's incorrect. See my other reply for details.
>
>>  There 2 of those on eMMC and they are _NOT_ accessible in
>>  this fashion. Neither they bear any FS on them.
>
> The boot HW partitions are block storage just like any other. SW can place 
> whatever data structures it wants into these HW partitions; the 
> interpretation of any data stored here is up to the SW or HW that reads and 
> interprets it, e.g. a SoC boot ROM. While many systems will place raw data 
> here, others certainly do place SW partition tables, and perhaps even 
> filesystems, in the HW partitions.

That would've meant something has changed since last year. Will check
tomorrow when I'm back at my desk.

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