FIT image: load secure FPGA

["Jorge Ramirez-Ortiz, Foundries" <jorge@foundries.io>]

Hello,

We are enabling secure boot on Zynqmp with SPL.

The issue however is that during secure boot, the bootrom not only
validates the first loader (SPL and PMUFW combo) but it will also
expect a signed bitstream during load(FPGA).

Since currently the SPL load of an FPGA image from FIT does not
support loading images for authentication (fpga_loads), I'd like to
discuss how to best implement such support.

A pretty standard file.its description of the FPGA loadable looks like
this:

 fpga {
      description = "FPGA binary";
      data = /incbin/("${DEPLOY_DIR_IMAGE}/${SPL_FPGA_BINARY}");
      type = "fpga";
      arch = "${UBOOT_ARCH}";
      compression = "none";
      load = <${fpgaloadaddr}>;
      hash-1 {
      	     algo = "${FIT_HASH_ALG}";
	     };
      };

We could extend imagetool.h struct image_tool_params to add more
params or perhpas just define different 'types' of fpga?

Something like:
  "fpga"
  "fpga-auth" : authenticated
  "fpga-enc"  : encrypted
  "fpga-sec"  : encrypted and authenticated

Then it would be a matter of modifying
https://github.com/u-boot/u-boot/blob/master/common/spl/spl_fit.c#L572

any thoughts?

TIA
Jorge