I am performing a warm boot (asserting PS_POR_B) on ZCU102 and the CSU ROM gives me error code 0x23 (XCBR_STAGE2_QSPI_24_INIT_ERROR) which means it did not find the "Image Identification" field in the image.
This only happens if u-boot is run prior to the PS_POR_B assertion.
Only a complete power cycle of the board allows the ZU+ device to reboot successfully in QSPI24 mode.
This happens because the ZCU102 has larger than 16MB flashes and u-boot always accesses them in 4-bytes addressing.
The flash cannot be accessed in 3-bytes addressing (which is what CSU ROM uses in QSPI24) unless it gets reset (by a power cycle).
The work-around is to always boot in QSPI32 (4-bytes addressing) when flashes larger than 16MB are used.