[U-Boot] [BISECTED] [BUG]: MMC initialization hang at Zynq Z-turn board

[Matwey V. Kornilov]

Hello,

I am running Zynq Z-turn board and I face the following issue with MMC
initialization in SPL.
With u-boot master, I see the message similar to the following:

U-Boot SPL 2019.07-00352-gb5f3eb3393 (Jul 31 2019 - 20:03:42 +0300)
mmc boot
Trying to boot from MMC1

Then, the u-boot waits forever. I've tried to add debug prints and
found that execution is stalled somewhere inside mmc_init().
Using bisect I've found that the following broken commit is the following:

commit 3d296365e4e8823c7c0d4b568fa7accfae4bf895 (refs/bisect/bad)
Author: Faiz Abbas <faiz_abbas at ti.com>
Date:   Tue Jun 11 00:43:34 2019 +0530

    mmc: sdhci: Add support for sdhci-caps-mask

    Add Support for masking some bits in the capabilities
    register of a host controller.

    Also remove the redundant readl() into caps1.

    Signed-off-by: Faiz Abbas <faiz_abbas at ti.com>
    Reviewed-by: Tom Rini <trini at konsulko.com>

Until that commit the behavior was the following:

U-Boot SPL 2019.07-00351-g889a4dfc55 (Jul 31 2019 - 20:01:41 +0300)
mmc boot
Trying to boot from MMC1
spl_load_image_fat_os: error reading image system.dtb, err - -2
spl_load_image_fat: error reading image u-boot.img, err - -2
SPL: failed to boot from all boot devices
### ERROR ### Please RESET the board ###

There were no u-boot.img at the SD card while testing, so this error
message is expected here.
5456935a1da3 ("ARM: zynq: Add configuration for Z-turn board") was
applied at the top of every testing commit to allow the board
initialization in SPL.

What could be wrong with that commit and how could I fix the board?

-- 
With best regards,
Matwey V. Kornilov