Description
Due to a problem in the Quartus® Prime Pro Edition Software v21.1 and above, when using the Stratix® 10 FPGA or all Agilex™ devices, the Mailbox Client IP will return data of 0x0 when performing the QSPI_READ operation that reads multiple flash sectors at a time.
This is due to a bug in the SDM firmware that prevents the QSPI_READ operation from being issued to the configuration flash device.
Resolution
To work around this problem, execute QSPI_READ operations until the sector boundary and perform another QSPI_READ operation for the next sector.
This problem is scheduled to be fixed in a future release of the Quartus® Prime Pro Edition Software.