I’m facing with the same problem. A small investigation shows that the problem is quite old. Unfortunately, there is no CONFIG_MMC_UNSAFE_RESUME in the modern kernel. But, in fact, another solution has been found - adding the “expecting_media_change” flag. Moreover, the code was merged, but it disappears in the last kernel version. Why? I tried to revert it back and it looks like everything works! There is only one drawback - you must not remove sdcard during suspend, and this limitation is ok for me.