[CPUFREQ] powernow-k8: Set transition latency to 1 if ACPI tables export 0

This doesn't fix anything, but it's expected that a transition latency of 0
could cause trouble in the future.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Cc: Langsdorf, Mark <mark.langsdorf@amd.com>
Signed-off-by: Dave Jones <davej@redhat.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
index cf52215d9eb1..935989693a64 100644
--- a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
+++ b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
@@ -1046,6 +1046,19 @@ static int get_transition_latency(struct powernow_k8_data *data)
 		if (cur_latency > max_latency)
 			max_latency = cur_latency;
 	}
+	if (max_latency == 0) {
+		/*
+		 * Fam 11h always returns 0 as transition latency.
+		 * This is intended and means "very fast". While cpufreq core
+		 * and governors currently can handle that gracefully, better
+		 * set it to 1 to avoid problems in the future.
+		 * For all others it's a BIOS bug.
+		 */
+		if (!boot_cpu_data.x86 == 0x11)
+			printk(KERN_ERR FW_WARN PFX "Invalid zero transition "
+				"latency\n");
+		max_latency = 1;
+	}
 	/* value in usecs, needs to be in nanoseconds */
 	return 1000 * max_latency;
 }