[M] Change in coreboot[master]: vc/amd/*,soc/amd/*: Add SVC call to get HSP Secure State

[Jon Murphy (Code Review)]

Attention is currently required from: Jason Glenesk, Raul Rangel, Martin L Roth, Matt DeVillier, Name of user not set #1004763, Martin Roth, Fred Reitberger, Karthik Ramasubramanian, Felix Held.

Jon Murphy has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/71207 )

Change subject: vc/amd/*,soc/amd/*: Add SVC call to get HSP Secure State
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Patch Set 4:

(1 comment)

File src/vendorcode/amd/fsp/cezanne/include/bl_uapp/bl_syscall_public.h:

https://review.coreboot.org/c/coreboot/+/71207/comment/adebbbba_98a13af1 
PS1, Line 362: uint32_t svc_get_hsp_secure_state(uint32_t *hsp_secure_state);
> So looking into it further, I think these calls need a bit of a redesign. […]

Maybe I'm not following, but the function itself is defined in svc.c and calls into the PSP function there.  It looks like svc_get_prev_boot_status has the same implementation as svc_get_hsp_secure_state with the prototypes and definitions in the same places even though it's not supported by cezanne and picasso.

I agree that we shouldn't be declaring prototypes in code bases that aren't using them, but it looks like there's more cleanup to be done.

What about declaring a default implementation weak in the common code that just returns an unimplemented status?  Then platforms that implement the call can override?  That's how we handle GPIO's in boards.

I suppose we could also have a platform_psp call in svc.c that's a nop on previous platforms, but you can add whatever is unique to your platform there?  I think the biggest issue is we want this to be called as a part of the boot flow, but the boot flow and feature sets aren't 1:1 across platforms.

I can put additional cleanup CL's on this stack after we agree on the way to handle it.