The datasheet states: For normal SPI operation, these pins should be tied to
AGND through a 100 kΩ resistor on each pin. These pins are both 1.8 V and 3.3 V
tolerant. However, the SDIO output logic level is dependent on the bias of the
SPIVDD pin. For 3.3 V output logic, tie SPIVDD to 3.3 V (AVDD2). For 1.8 V
output logic, tie SPIVDD to 1.8 V (AVDD1).
My question is whether the SPIVDD can be tied to 2.5V to be compatible to the
2.5V logic, since some FPGAs are 2.5V logic?
Yes, you can connect the SPIVDD to 2.5V to make it compatible with the 2.5V