[PATCH] x86-64: Disable local APIC timer use on AMD systems with C1E

AMD dual core laptops with C1E do not run the APIC timer correctly
when they go idle. Previously the code assumed this only happened
on C2 or deeper.  But not all of these systems report support C2.

Use a AMD supplied snippet to detect C1E being enabled and then disable
local apic timer use.

This supercedes an earlier workaround using DMI detection of specific systems.

Thanks to Mark Langsdorf for the detection snippet.

Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 34 insertions, 0 deletions

diff --git a/arch/i386/kernel/cpu/amd.c b/arch/i386/kernel/cpu/amd.c
index 41cfea57232b..2d47db482972 100644
--- a/arch/i386/kernel/cpu/amd.c
+++ b/arch/i386/kernel/cpu/amd.c
@@ -22,6 +22,37 @@
 extern void vide(void);
 __asm__(".align 4\nvide: ret");
 
+#define ENABLE_C1E_MASK         0x18000000
+#define CPUID_PROCESSOR_SIGNATURE       1
+#define CPUID_XFAM              0x0ff00000
+#define CPUID_XFAM_K8           0x00000000
+#define CPUID_XFAM_10H          0x00100000
+#define CPUID_XFAM_11H          0x00200000
+#define CPUID_XMOD              0x000f0000
+#define CPUID_XMOD_REV_F        0x00040000
+
+/* AMD systems with C1E don't have a working lAPIC timer. Check for that. */
+static __cpuinit int amd_apic_timer_broken(void)
+{
+	u32 lo, hi;
+	u32 eax = cpuid_eax(CPUID_PROCESSOR_SIGNATURE);
+	switch (eax & CPUID_XFAM) {
+	case CPUID_XFAM_K8:
+		if ((eax & CPUID_XMOD) < CPUID_XMOD_REV_F)
+			break;
+	case CPUID_XFAM_10H:
+	case CPUID_XFAM_11H:
+		rdmsr(MSR_K8_ENABLE_C1E, lo, hi);
+		if (lo & ENABLE_C1E_MASK)
+			return 1;
+                break;
+        default:
+                /* err on the side of caution */
+		return 1;
+        }
+	return 0;
+}
+
 static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 {
 	u32 l, h;
@@ -241,6 +272,9 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 
 	if (cpuid_eax(0x80000000) >= 0x80000006)
 		num_cache_leaves = 3;
+
+	if (amd_apic_timer_broken())
+		set_bit(X86_FEATURE_LAPIC_TIMER_BROKEN, c->x86_capability);
 }
 
 static unsigned int __cpuinit amd_size_cache(struct cpuinfo_x86 * c, unsigned int size)