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

[Ziyuan]

hi Stephen,

On 03/14/2017 12:41 PM, Stephen Warren wrote:
> On 03/13/2017 06:54 PM, Ziyuan wrote:
>> hi Stephen,
>>
>> On 03/14/2017 05:49 AM, 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.
>>
>> The 4th of "mmc dev 0 1" is the *software* partition index, not the hw
>> partition index. AKA eMMC has four partitions: user
>> data/boot0/boot1/rpmb, I think Tim wanna to boot from other partition,
>> like boot0, right?
>
> The fourth parameter is the HW partition number. See how cmd/mmc.c's 
> do_mmc_dev() passes this value to blk_select_hwpart_devnum(), then to 
> blk_select_hwpart().

Thanks, it's my fault.

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