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authorAndi Kleen <ak@suse.de>2008-01-30 13:33:16 +0100
committerIngo Molnar <mingo@elte.hu>2008-01-30 13:33:16 +0100
commit0c07ee38c9d4eb081758f5ad14bbffa7197e1aec (patch)
treef32f5dba9b03b9fa5ac262a2c569b43ae9d0994e /arch/x86/kernel/process_64.c
parent30d432dfab2bcfd021d352e2058fae6b9405caeb (diff)
x86: use the correct cpuid method to detect MWAIT support for C states
Previously there was a AMD specific quirk to handle the case of AMD Fam10h MWAIT not supporting any C states. But it turns out that CPUID already has ways to detectly detect that without using special quirks. The new code simply checks if MWAIT supports at least C1 and doesn't use it if it doesn't. No more vendor specific code. Note this is does not simply clear MWAIT because MWAIT can be still useful even without C states. Credit goes to Ben Serebrin for pointing out the (nearly) obvious. Cc: "Andreas Herrmann" <andreas.herrmann3@amd.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/kernel/process_64.c')
-rw-r--r--arch/x86/kernel/process_64.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 4e65ae8a54b..dbe0a846ec5 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -280,10 +280,19 @@ static void mwait_idle(void)
}
}
+
+static int mwait_usable(const struct cpuinfo_x86 *c)
+{
+ if (force_mwait)
+ return 1;
+ /* Any C1 states supported? */
+ return c->cpuid_level >= 5 && ((cpuid_edx(5) >> 4) & 0xf) > 0;
+}
+
void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
{
static int printed;
- if (cpu_has(c, X86_FEATURE_MWAIT)) {
+ if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
/*
* Skip, if setup has overridden idle.
* One CPU supports mwait => All CPUs supports mwait