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

[Alexander Graf]

On 06.12.2012, at 20:11, Gabriel L. Somlo wrote:

> On Thu, Dec 06, 2012 at 06:10:46PM +0100, Alexander Graf wrote:
>>> If I could figure out how to write a reliable _STA method for the SMC,
>>> that would detect whether or not it was supplied as "-device applesmc"
>>> on the qemu command line, I think we might be on to something...
>> 
>> You should be able to poke fw_cfg in the _STA method. The machine file could search its bus on init (or on machine create notify) and populate a fw_cfg variable to indicate whether it found an applesmc.
> 
> So the fw_cfg looks like this in 'info qtree':
> 
>  dev: fw_cfg, id ""
>    ctl_iobase = 0x510
>    data_iobase = 0x511
>    irq 0
>    mmio ffffffffffffffff/0000000000000002
>    mmio ffffffffffffffff/0000000000000001
> 
> I'm confused by the mmio values (start at the very top of memory, go
> for one or two bytes from there ?)

No idea what they're doing there. Just ignore them for now.

> I also found this patch by Gerd, which doesn't seem to have made it
> upstream (yet):
> 
> http://www.mail-archive.com/qemu-devel@nongnu.org/msg110131.html
> 
> That patch suggests that I could just write stuff to 0x510 and read
> from 0x511, and if I get it "right" the values I read will end up
> making sense :)

Yup :). And the value could be the STA result.

> Can anyone can point me to an example of how to interact with fw_cfg ?

Sure! Check out

  http://git.qemu.org/?p=qemu.git;a=blob;f=pc-bios/optionrom/optionrom.h;h=3daf7da49576091e337b1dab814e87310d5ea25f;hb=HEAD


Alex