Why is the Intel Agilex® FPGA QSPI controller disabled during FPGA configuration?

In the Intel® Quartus® Prime Pro Edition Software version 21.1 and prior, there is a problem  with the Intel Agilex® FPGA SDM QSPI controller being disabled for the HPS after the initial FPGA configuration occurs during HPS boot first mode.  This occurs after the first FPGA configuration from both U-Boot and/or Linux.

To work around this problem, you can re-probe the QSPI flash driver after the initial FPGA configuration.

To re-probe in U-Boot, run this commmand:

SOCFPGA_AGILEX # sf probe

This problem is scheduled to be fixed in a future release of Intel® Quartus® Prime Pro Edition Software.