HPS boot from SDCARD with pins routed to FPGA

[Altera_Forum]

Hello,  

Does anybody could help me telling if is it possible to boot HPS from SDCARD (bootsel = 0x05), with SDCARD pins routed to FPGA (assume FPGA is already configured when HPS boot). I supposed it is possible, since at Qsys, on HPS peripheral pins configuration tab SDIO pin accepts FPGA (Full mode) and HPSI/O Set 0 options.  Does anybody here have already boot HPS from an SDCARD this way?  I know that some logic is necessary at FPGA side to deal with bidirectional pins (Data and CMD) but since HPS export the output_enables, it is not complicated to be done.  Thank you in advance,  Lucas

[Altera_Forum]

Hello, I believe this is not possible. The BSEL of 0x05 is meant to tell the Boot ROM to set up the necessary HPS IO and copy the preloader to be executed on On-chip RAM. As such, I don't think the Boot ROM has the ability to look for the preloader from the FPGA I/O. Nonetheless, you can set the device to boot from FPGA on chip RAM instead - which is actually quite easy to be done.

[Altera_Forum]

Thank you, sunshine. You pointed me to the right direction...  

I will put preloader at FPGA (on chip RAM) , after that the HPS I/O pins will be ready to read SDCARD from FPGA (I supose) so HPS can read u-boot.img from SDCARD. Is that right?

[Altera_Forum]

I believe some modification to the preloader is required (to point it to the correct address, among others). it is also worth to double check the system manager register settings to make sure that the SD interface to FPGA is enable, and that the I/O timing in the FPGA is meet (meaning, no timing failure during compilation)