[Karmic] SRU: Fix boot hang on Acer TravelMate 2440

[Stefan Bader]

SRU Justification:

Impact: Upstream changes between Jaunty and Karmic disabled the ARB_DISABLE
call as it is a NOP on recent platforms. However the test for CPU model
and version missed some systems which then hang on boot.

Fix: The following patch has been tested and was submitted upstream,
but has not been picked up, yet (but IMO is just a matter of time).
As it is a regression agains Jaunty and the impact is a non-working
system, I think this should be taken ahead of stable. It should be
safe as well as it just reduces the number of systems which get handled
the new way.

Testcase: Boot of affected systems hangs without patch.



To: lenb at kernel.org
Cc: linux-acpi at vger.kernel.org, Zhao Yakui <yakui.zhao at intel.com>,
        stable at kernel.org
Subject: [Resend PATCH] acpi: Use the ARB_DISABLE for the CPU which model id is less than 0x0f.
Date:	Fri, 11 Dec 2009 15:17:20 +0800
From: Zhao Yakui <yakui.zhao at intel.com>

OriginalSource: linux-acpi mailing list
BugLink: http://bugs.launchpad.net/bugs/481765

ARB_DISABLE is a NOP on all of the recent Intel platforms. For such platforms,
reduce contention on c3_lock by skipping the fake ARB_DISABLE.

The cpu model id on one laptop is 14. If we disable ARB_DISABLE on this box,
the box can't be booted correctly. But if we still enable ARB_DISABLE on this
box, the box can be booted correctly.

So we still use the ARB_DISABLE for the cpu which mode id is less than 0x0f.

http://bugzilla.kernel.org/show_bug.cgi?id=14700

Signed-off-by: Zhao Yakui <yakui.zhao at intel.com>
Acked-by: Pallipadi, Venkatesh <venkatesh.pallipadi at intel.com>
cc: stable at kernel.org
Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
---
 arch/x86/kernel/acpi/cstate.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index 59cdfa4..2e837f5 100644
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -48,7 +48,7 @@ void acpi_processor_power_init_bm_check(struct acpi_processor_flags *flags,
 	 * P4, Core and beyond CPUs
 	 */
 	if (c->x86_vendor == X86_VENDOR_INTEL &&
-	    (c->x86 > 0xf || (c->x86 == 6 && c->x86_model >= 14)))
+	    (c->x86 > 0xf || (c->x86 == 6 && c->x86_model >= 0x0f)))
 			flags->bm_control = 0;
 }
 EXPORT_SYMBOL(acpi_processor_power_init_bm_check);
-- 
1.5.4.5

--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo at vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html