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| author | Andreas Mohr <[andi@rhlx01.fht-esslingen.de]> | 2006-06-26 21:58:00 +0200 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2006-06-28 09:27:02 +0200 |
| commit | b488f02156d3deb08f5ad7816d565c370a8cc6f1 (patch) | |
| tree | 7ba4c86b66451780a39c28b618dcfa8037584cb2 /block/deadline-iosched.c | |
| parent | ACPIPHP: prevent duplicate slot numbers when no _SUN (diff) | |
| download | linux-b488f02156d3deb08f5ad7816d565c370a8cc6f1.tar.xz linux-b488f02156d3deb08f5ad7816d565c370a8cc6f1.zip | |
ACPI: restore comment justifying 'extra' P_LVLx access
While trying to look for superfluous I/O accesses that can be optimized
away, I stumbled upon this ACPI sleep I/O access and couldn't figure out
why the hell this dummy op was necessary.
After more than one hour of internet research, I had collected a sufficient
number of documents (among those very old kernel versions) that finally
told me what this dummy read was about: STPCLK# doesn't get asserted in time
on (some) chipsets, which is why we need to have a dummy I/O read to delay
further instruction processing until the CPU is fully stopped.
Signed-off-by: Andreas Mohr <andi@lisas.de>
Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'block/deadline-iosched.c')
0 files changed, 0 insertions, 0 deletions