cpufreq: Add warning message to powernow-k8

cpufreq modules are often loaded from init scripts that assume that
all recent AMD systems will use powernow-k8.
To inform the user of the change of support and ease the transition
to acpi-cpufreq, emit a warning message.
Signed-off-by: NAndre Przywara <andre.przywara@amd.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

drivers/cpufreq/Kconfig.x86

@@ -96,7 +96,8 @@ config X86_POWERNOW_K8
 	select CPU_FREQ_TABLE
 	depends on ACPI && ACPI_PROCESSOR
 	help
-	  This adds the CPUFreq driver for K8/K10 Opteron/Athlon64 processors.
+	  This adds the CPUFreq driver for K8/early Opteron/Athlon64 processors.
+	  Support for K10 and newer processors is now in acpi-cpufreq.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called powernow-k8.

drivers/cpufreq/powernow-k8.c

@@ -1563,6 +1563,9 @@ static int __cpuinit powernowk8_init(void)
 	if (!x86_match_cpu(powernow_k8_ids))
 		return -ENODEV;
 
+	if (static_cpu_has(X86_FEATURE_HW_PSTATE))
+		pr_warn(PFX "support for this CPU is deprecated, use acpi-cpufreq instead.\n");
+
 	for_each_online_cpu(i) {
 		int rc;
 		smp_call_function_single(i, check_supported_cpu, &rc, 1);