Hi,
Beaglebone black (am335x_evm_defconfig) is broken (with MMC boot and u-boot.img on ext4 partition). I bisected it to commit fd61d39970b9901217efc7536d9f3a61b4e1752a spl: mmc: add break statements in spl_mmc_load_image() from Nikita Kiryanov (in Cc).
Working image gives: ******************************************************************************** U-Boot SPL 2016.01-rc1-00036-g483ab3d (Feb 16 2016 - 19:04:10) bad magic bad magic spl_register_fat_device: fat register err - -1 spl_register_fat_device: fat register err - -1 spl_load_image_fat: error reading image u-boot.img, err - -1 spl: ext4fs_open failed spl: ext4fs_open failed spl_load_image_ext: error reading image uImage, err - -1
U-Boot 2016.01-rc1-00033-g9884f44 (Feb 16 2016 - 18:55:52 +0100) ********************************************************************************
Since this commit, we get: ******************************************************************************** U-Boot SPL 2016.01-rc1-00037-gfd61d39 (Feb 16 2016 - 19:01:54) bad magic bad magic ### ERROR ### Please RESET the board ### ********************************************************************************
Guillaume