Why do I get return data of 0x0 when performing a QSPI_READ operation on certain sectors using the Mailbox Client Intel® FPGA IP?

Due to a problem in the Intel® Quartus® Prime Pro Edition Software v21.1 and above, when using Intel® Stratix® 10 or all Intel Agilex® devices, the Mailbox Client Intel® FPGA 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 firmware bug in the SDM firmware when issuing the QSPI_READ operation to the configuration flash device.

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 Intel® Quartus® Prime Pro Edition Software.