linux-kernel - RE: [PATCH] ACPI: resume: re-enable SCI-enable workaround

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Date:	Fri, 15 May 2009 23:50:09 -0700
From:	"Moore, Robert" <robert.moore@...el.com>
To:	Len Brown <lenb@...nel.org>
CC:	Bob Copeland <me@...copeland.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Lin, Ming M" <ming.m.lin@...el.com>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	"Zhao, Yakui" <yakui.zhao@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: RE: [PATCH] ACPI: resume: re-enable SCI-enable workaround

ACPICA did not change the SCI_EN value. The #define associated with the control register has always been 0x0201 in ACPICA.

A linux patch changes the value from 0x0201 to 0x0200, and represents a divergence of linux from ACPICA.

What ACPICA did was to rename the #define, that is what broke the linux patch.


- #define ACPI_PM1_CONTROL_PRESERVED_BITS         0x0201  /* Bit 9, Bit 0 (SCI_EN) */


+ #define ACPI_PM1_CONTROL_IGNORED_BITS           0x0201  /* Bits 9, 0(SCI_EN) */
+ #define ACPI_PM1_CONTROL_RESERVED_BITS          0xC1F8  /* Bits 14-15, 3-8 */
+#define ACPI_PM1_CONTROL_PRESERVED_BITS \
+         (ACPI_PM1_CONTROL_IGNORED_BITS | ACPI_PM1_CONTROL_RESERVED_BITS)




>-----Original Message-----
>From: Len Brown [mailto:lenb@...nel.org]
>Sent: Friday, May 15, 2009 10:50 PM
>To: Moore, Robert
>Cc: Bob Copeland; Rafael J. Wysocki; Lin, Ming M; Bjorn Helgaas; Zhao,
>Yakui; linux-kernel@...r.kernel.org; linux-acpi@...r.kernel.org
>Subject: RE: [PATCH] ACPI: resume: re-enable SCI-enable workaround
>
>
>> >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
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