Using I2S to config FPGA | Cypress Semiconductor
Using I2S to config FPGA
In GPIF 32-bit mode, SPI is not available. Although there is an app note (AN84868) on this topic, but it involves reconfiguring the GPIF to 32-bit after FPGA configuration. To avoid this 2-step process, I'm thinking if it's possible to use the CLK and Data pins of I2S in native mode (not bit banging) to config FPGA in slave serial mode.