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From: Len Brown <lenb@kernel.org>
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To: "Moore, Robert" <robert.moore@intel.com>
Cc: Bob Copeland <me@bobcopeland.com>, "Rafael J. Wysocki" <rjw@sisk.pl>,
       "Lin, Ming M" <ming.m.lin@intel.com>,
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Subject: RE: [PATCH] ACPI: resume: re-enable SCI-enable workaround
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> >The BIOS bug workaround mistakenly got disabled
> >when we followed the ACPI specification more closely
> >by ignoring OS updates to that bit.
> 
> Not exactly. ACPICA has always preserved the SCI_EN bit. Linux apparently has a "linux-only" patch to ACPICA that disables this.
> 
> The recent version of ACPICA change the #define enough such that the patch no longer works.

"We" here means Linux, and thus the description is accurate.

The fact is that in 2.6.29 Linux had
ACPI_PM1_CONTROL_PRESERVED_BITS 0x0200
and when "we" updated it to 0x201 via the ACPICA update,
the workaround in the Linux resume code became a NOP.

-Len