BOOT From eMMC on SDMMC2 in 4-bit mode

[Jboui.450]

Hello,

we would like to boot from a eMMC memory on our board connected to SDMMC2.

As the camera interface is in conflic with SDMMC2 8bit mode, we must configure it as a SDMMC 4 bit width.

The question is will we still me able to boot from our eMMC memory in 4 bit mode as we do in 8 bit ?

The memory we use is the following MTFC4GACAJCN-1M from Micron

Tanks for your support.

[PatrickF]

At HW level, there is no issue to use 4-bit eMMC as BootROM first boot level only use one data line, e.g. CLK/CMD and D0 on PE3/PG6 and PB14 (see AN5031).

To restrict usage to 4-bit eMMC in TF-A and uBoot/Linux, you should adapt the Device Tree.

Please note that we currently have a limitation for eMMC boot from Micron devices, see ES0438. Meanwhile you should use Toshiba or Kingston devices. This will be solved in future silicon.