[U-Boot] eMMC boot partition support in uboot

[Richard Retanubun <richardretanubun@ruggedcom.com>]

Hi guys,

Recap: I am trying to boot MLO + uboot from eMMC boot partition on DRA7xx_EVM eval platform.
SW-Baseline: uboot p-ti-uboot-2013.04 & p-ti-linux-3.8.y from omapzoom.

What happens so far:
1. I am able to dd the MLO into /dev/mmcblk1boot0 (need to echo 0 to force_ro).
2. I am able to setup the eMMC to enable the ROM BootLoader (RBL) to boot the "Alternate boot mode"
    using mmc-utils by setting:
    BOOT_BUS_WIDTH Register   (EXT_CSD [177]) = 0x15 (needed to set DDR mode at boot)
    PARTITION_CONFIG Register (EXT_CSD [179]) = 0x48 (needed to enable booting from boot partition)

    Up to this point I am able to get this response when booting the MLO from the eMMC boot partition

U-Boot SPL 2013.04-00366-g5f72750-dirty (Dec 03 2013 - 21:40:19)
DRA752 ES1.0
OMAP SD/MMC: 1
spl: wrong MMC boot mode
spl_mmc_load_image:
         spl_boot_mode = 0 (MMCSD_MODE_UNDEFINED)
         spl_boot_device = 6 (BOOT_DEVICE_MMC2)
### ERROR ### Please RESET the board ###

3. I realize that the MLO contents (using uboot/tools/omapimage?) needed to say
    MMCSD_MODE_RAW for my platform. I am bypassing this problem by by hard coding the response
    arch/arm/cpu/armv7/omap-common/boot-common.c::spl_boot_mode() to always says MMCSD_MODE_RAW.
    This seems to work and I am past the hang() code.

4. Now, MLO is ready to (raw) load uboot binary from the eMMC boot partition (i.e. /dev/mmcblk1boot0).
    Unfortunately, at this point I don't know how to make the platform recognize the eMMC boot partitions.
    I think they are not modelled yet in uboot. Only the User-Data-Area (UDA)
    is recognized in uboot (called mmc 1)

    My understanding is that for mmc boot partition recognition, we need to
    extend drivers/mmc/omap_hsmmc.c::omap_mmc_init() to be able to handle it?
    or is there a better place?

Question 1:
Is my understanding of the current state all correct?

Question 2:
How should I proceed to add support for /dev/mmcblk1boot0 into uboot?
I am thinking the solution should self parse the ext_csd to find out which boot
partition is active and then load the uboot raw from a known offset there.

I saw the linux patch adding eMMC boot partition at:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/Documentation/mmc/mmc-dev-parts.txt?id=371a689f64b0da140c3bcd3f55305ffa1c3a58ef

But I don't see how to adapt it into uboot...

Thanks for everyone's time.