ATF can leave the MMC IP in a state where U-Boot mmc driver
can't enumerate the eMMC.
This patch provides a mmc0_reset_clk() function like we
already so do sd card controller which resets the IP
when entering U-Boot.
With this patch applied eMMC partitions are successfully
enumerated again.
=> mmc dev 0
switch to partitions #0, OK
mmc0(part 0) is current device
=> mmc part
Partition Map for MMC device 0 -- Partition Type: EFI
Part Start LBA End LBA Name
Attributes
Type GUID
Partition GUID
1 0x00000800 0x00000fff "vrl"
attrs: 0x0000000000000000
type: ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
guid: 496847ab-56a1-4cd5-a1ad-47f4acf055c9
2 0x00001000 0x000017ff "vrl_backup"
attrs: 0x0000000000000000
type: ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
guid: 61a36fc1-8efb-4899-84d8-b61642efa723
3 0x00001800 0x00001fff "mcuimage"
<snip>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>