From: Andi Kleen <ak@suse.de>
Date: Thu, 16 Feb 2006 22:42:04 +0000 (+0100)
Subject: [PATCH] x86_64: Don't enable ATI apicmaintimer workaround when the machine has C2... 
X-Git-Tag: v2.6.16-rc4~35
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ab68805955ee3dd84a6aa76cd70e61fde996968d;p=linux-2.6

[PATCH] x86_64: Don't enable ATI apicmaintimer workaround when the machine has C2 or C3

Many laptops have problems with ticking the local APIC timer in C2/C3.
The code added earlier to use it by default on ATI didn't really work
for them. Don't enable it when the system supports C2/C3.

This doesn't fix the problem fully, but at least it's not worse than before.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/arch/x86_64/kernel/io_apic.c b/arch/x86_64/kernel/io_apic.c
index 4282d72b2a..2585c1d92b 100644
--- a/arch/x86_64/kernel/io_apic.c
+++ b/arch/x86_64/kernel/io_apic.c
@@ -30,6 +30,9 @@
 #include <linux/mc146818rtc.h>
 #include <linux/acpi.h>
 #include <linux/sysdev.h>
+#ifdef CONFIG_ACPI
+#include <acpi/acpi_bus.h>
+#endif
 
 #include <asm/io.h>
 #include <asm/smp.h>
@@ -260,6 +263,8 @@ __setup("apic", enable_ioapic_setup);
 
    And another hack to disable the IOMMU on VIA chipsets.
 
+   ... and others. Really should move this somewhere else.
+
    Kludge-O-Rama. */
 void __init check_ioapic(void) 
 { 
@@ -307,6 +312,17 @@ void __init check_ioapic(void)
 				case PCI_VENDOR_ID_ATI:
 					if (apic_runs_main_timer != 0)
 						break;
+#ifdef CONFIG_ACPI
+					/* Don't do this for laptops right
+					   right now because their timer
+					   doesn't necessarily tick in C2/3 */
+					if (acpi_fadt.revision >= 3 &&
+			(acpi_fadt.plvl2_lat + acpi_fadt.plvl3_lat) < 1100) {
+						printk(KERN_INFO
+"ATI board detected, but seems to be a laptop. Timer might be shakey, sorry\n");
+						break;
+					}
+#endif					
 					printk(KERN_INFO
 	     "ATI board detected. Using APIC/PM timer.\n");
 					apic_runs_main_timer = 1;