[U-Boot] CONFIG_ENV_IS_IN_UBI not working nicely with CONFIG_SPI_FLASH_MTD

I have been using u-boot with CONFIG_SPI_FLASH_MTD. This has allowed me to use MTD/UBI/UBIFS with SPI flash. I now want to use CONFIG_ENV_IS_IN_UBI, but after enabling this, u-boot can't read the environment on start-up:

=== U-Boot 2015.07 (Sep 24 2015 - 17:10:41 -0700)

Model: Zynq Zed Development Board I2C: ready DRAM: ECC disabled 512 MiB MMC: zynq_sdhci: 0 Device nor0 not found! Error initializing mtdparts!

** Cannot find mtd partition "uboot-env-itb" Using default environment ===

"mtdparts" and "saveenv" do not work until after I do "sf probe".

I'm using u-boot on a Zynq 7020 SoC. Can someone help me with what sf probe-equivalent function call to make and where? I'm guessing in board_init_f() or board_init_r()?

Thanks for your help.