[U-Boot] [U-BOOT] [PATCH] mmc: enable switch partition function

[Lei Wen]

>
> I am thinking now approach for this.
> How about adding addtitional member in the mmc structure, like part.
> During mmc probe, the driver could know whether the device support partition
> switch or not, if it support, we could register three other "faked" mmc device
> corresponding to two boot partition, and RPMB partition.
>
> Then we could use the current command to access the different hardware
> partition in the emmc. Like if we are accessing one hardware partition, we need
> to send switch command first. If the part member in the mmc is a invalid value,
> we then don't send that switch partition command.
>
> Could this approach be acceptable?
>

Further refine this idea, don't need to call mmc_register multi-times.
For the purpose is to switch partition when needed, we really do want to one
real device. So I propose a new solution as:

Assume there is two sd/mmc controller on the board, named as mmc0&mmc1.
The mmc0 attach with a sd card, and mmc1 attach with a emmc that has partition
supported. Then we would have mmc(2, 3, 4, 5, 6, 7, 8) faked device map to mmc0
, mmc(9, 10, 11, 12, 13, 14, 15) map to mmc1.

Give the command as "mmc read 9 0x1000000 0 0x10", uboot would get the
real device
num by 9/7, while hardware part num is (9-1-7*real_dev_num) that is 1.
So we need
to make mmc1 send the switch part 1 command to the emmc, then perform the read
operation.

If we want to run "mmc read 5 0x10000 0x10 0x5", the sd attach on mmc0 has no
hardware partition suppport, it would simply refuse to execute that command.
Or if we want to be more gracefully handled, we could let the read 5
perform like the
read 0 command.

Best regards,
Lei