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

[Alexander Graf]

On 11.12.2012, at 07:57, Gerd Hoffmann  wrote:
> 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:
> >
> > 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.

So what if SeaBIOS maps some PCI BAR to 0x300 with a device that goes wild if you write that detection sequence?

The whole point of a DSDT is to free the OS from probing devices.

Alex
> >    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