| commit | b488f02156d3deb08f5ad7816d565c370a8cc6f1 | |
| author | Andreas Mohr <[andi@rhlx01.fht-esslingen.de]> | |
| Mon, 26 Jun 2006 19:58:00 +0000 (26 15:58 -0400) | ||
| committer | Len Brown <len.brown@intel.com> | |
| Wed, 28 Jun 2006 07:27:02 +0000 (28 03:27 -0400) | ||
| tree | 7ba4c86b66451780a39c28b618dcfa8037584cb2 | treesnapshot (tar.gz zip) |
| parent | 95b38b3f453c16de0f8cddcde3e71050bbfb37b9 | commitdiff |
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>
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>
| drivers/acpi/processor_idle.c | diffblobblamehistory |