[SeaBIOS] [PATCH 3/3] acpi: revert d9f5cdbdf (DSDT: Fix HPET _CRS Method)

[Gerd Hoffmann]

  Hi,

> But _INI relies on _STA being evaluated first, so unless I'm missing
> something that'd be a catch-22 :(

Oops, indeed.

> So, I can think of a couple of alternatives:
> 
> 	1. have a SMC._STA() method that queries something
> 
> 		a) could be fw_cfg (may require hacking
> 		   qemu/hw/applesmc.c *and* fw_cfg.c to make that happen)

I'd avoid fw_cfg if possible.

> 		b) could be the emulated SMC itself:
> 
> 			- right now, only the Data (0x300) and
> 			  Command (0x304) ports are ever read/written,
> 			  so we could set aside a magic qemu-smc-only
> 			  "port" (e.g. 0x308, but anything within the
> 			  32-byte range should work) and have it
> 			  always return a "magic" number when read
> 			  (via a qemu/hw/applesmc.c patch);

Sounds sensible.  Although the smc emulation in qemu looks incomplete,
there are a bunch of #defines which are never ever used.  Maybe a more
complete emulation offers a way to detect the smc without side effects.
 Failing that some magic register looks ok to me.  We should makes sure
this doesn't conflict with anything the real hardware does though.

> 		b) Kevin mentioned the SSDT and/or "BDAT" as other
> 		   potential mechanisms to make something like this

I don't think this helps much.  This just moves the smc detection from
AML code to C code (and BDAT would be used to store the result in a way
accessible from AML).

cheers,
  Gerd