[coreboot] AMD S3: Experiences with ACPI 2.0 method _BFS (Back From Sleep)

[Paul Menzel]

Dear coreboot folks,


Am Montag, den 18.02.2013, 17:09 +0100 schrieb Paul Menzel:

> searching for ACPI in the output of `dmesg` I noticed the following
> message.
> 
>         $ uname -v
>         #1 SMP Debian 3.2.35-2
>         $ dmesg | grep -i acpi
>         [    0.154063] ACPI: BIOS offers _BFS
>         [    0.154067] ACPI: If "acpi.bfs=1" improves resume, please notify linux-acpi at vger.kernel.org
> 
> Doing
> 
>    $ git grep _GTA
> 
> reveals that it is only implemented in the DSDT of AMD based boards.

Looking at the actual “implementation” it looks like it is not
implemented at all (see for AMD Thatcher’s DSDT) [1]. ;-)

        $ more src/mainboard/amd/parmer/dsdt.asl
        […]
        	/*
        	*	\_BFS OEM Back From Sleep method
        	*
        	*	Entry:
        	*		Arg0=The value of the sleeping state S1=1, S2=2
        	*
        	*	Exit:
        	*		-none-
        	*/
        	Method(\_BFS, 1) {
        		/* DBGO("\\_BFS\n") */
        		/* DBGO("From S") */
        		/* DBGO(Arg0) */
        		/* DBGO(" to S0\n") */
        	}
        […]

Would a patch be useful to remove that from all of the AMD DSDTs as Len
Brown wrote they requested to remove that from the next ACPI
specification?

For the curious, the method _BFS is documented in

    7.3.1 _BFS (Back From Sleep)

of the ACPI 4.0a specification [

> As resuming currently does not work on the ASRock E350M1 [1], I cannot
> test that.
> 
> Was this ever tested by adding `acpi.bfs=1` to the Linux kernel command
> line and what was the outcome? A test on AMD Persimmon would be very
> interesting.
> 
> It looks like support for this has been removed in the meantime though
> 
>         commit 3f6f49c7854c9294119437a82c5b35be78f9cea6
>         Author: Len Brown <len.brown at intel.com>
>         Date:   Thu Jul 26 20:08:54 2012 -0400
>         
>             ACPI: delete _GTS/_BFS support
> 
> since Linux Git tag v3.6-rc2.


Thanks,

Paul


> [1] http://www.coreboot.org/ASRock_E350M1
> [2] https://patchwork.kernel.org/patch/1246671/
[3] http://review.coreboot.org/gitweb?p=coreboot.git;a=blob;f=src/mainboard/amd/thatcher/dsdt.asl;h=4b600e84e023b305d767e5c087ba87f4d5fecd3f;hb=HEAD#l793
[4] http://www.acpi.info/spec40a.htm
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 198 bytes
Desc: This is a digitally signed message part
URL: <http://www.coreboot.org/pipermail/coreboot/attachments/20130218/021a2417/attachment.sig>