From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 9 Apr 2015 15:23:01 +0200
Subject: cpufreq: drop K8's driver from beeing selected
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.6/older/patches-4.6.2-rt5.tar.xz

Ralf posted a picture of a backtrace from

| powernowk8_target_fn() -> transition_frequency_fidvid() and then at the
| end:
| 932         policy = cpufreq_cpu_get(smp_processor_id());
| 933         cpufreq_cpu_put(policy);

crashing the system on -RT. I assumed that policy was a NULL pointer but
was rulled out. Since Ralf can't do any more investigations on this and
I have no machine with this, I simply switch it off.

Reported-by:  Ralf Mardorf <ralf.mardorf@alice-dsl.net>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/cpufreq/Kconfig.x86 |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/cpufreq/Kconfig.x86
+++ b/drivers/cpufreq/Kconfig.x86
@@ -123,7 +123,7 @@ config X86_POWERNOW_K7_ACPI
 
 config X86_POWERNOW_K8
 	tristate "AMD Opteron/Athlon64 PowerNow!"
-	depends on ACPI && ACPI_PROCESSOR && X86_ACPI_CPUFREQ
+	depends on ACPI && ACPI_PROCESSOR && X86_ACPI_CPUFREQ && !PREEMPT_RT_BASE
 	help
 	  This adds the CPUFreq driver for K8/early Opteron/Athlon64 processors.
 	  Support for K10 and newer processors is now in acpi-cpufreq.
