Am Montag, den 18.02.2013, 12:21 -0700 schrieb Marc Jones:
On Mon, Feb 18, 2013 at 9:24 AM, Paul Menzel wrote:
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@vger.kernel.orgDoing
$ git grep _GTA
for correctness, that was supposed to be `git grep _BFS`.
reveals that it is only implemented in the DSDT of AMD based boards.
The kernel sees the ACPI method, but doesn't do anything with it. If you would like the kernel to use the method, pass acpi.bfs=1.
Looking at the actual “implementation” it looks like it is not implemented at all (see for AMD Thatcher’s DSDT) [1]. ;-)
...
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.
Why would this be interesting? As noted, the method is present, but doesn't do anything.
So why is it there in the first place?
Some debug information could be enabled if the OS called the function.
I see.
I read the Linux ACPI message »If "acpi.bfs=1" improves resume, …« that way, that resume will be improved (by being quicker). I guess it was supposed to mean, »If your system has less problems with "acpi.bfs=1" than without, please …«.
Sorry for the confusion.
It looks like support for this has been removed in the meantime though
commit 3f6f49c7854c9294119437a82c5b35be78f9cea6 Author: Len Brown <len.brown@intel.com> Date: Thu Jul 26 20:08:54 2012 -0400 ACPI: delete _GTS/_BFS supportsince Linux Git tag v3.6-rc2.
The function is part of the spec up to 4.0 and Len recommends that it be remove it in the future revisions.
It seems safe to remove it, but it isn't causing harm and is part of the spec as implemented by coreboot.
True.
Thanks,
Paul