ACPI: Load acpi-cpufreq from processor driver automatically

The only left over hole in automatic cpufreq driver loading was the loading
of ACPI cpufreq. This driver should be loaded when ACPI supports a _PDC
method and the CPU vendor wants to use acpi cpufreq.

Simply add a request module call to the acpi processor core driver
when this is true. This seems like the simplest solution for this.

Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/acpi/processor_driver.c

@@ -497,6 +497,7 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
 
 #ifdef CONFIG_CPU_FREQ
 	acpi_processor_ppc_has_changed(pr, 0);
+	acpi_processor_load_module(pr);
 #endif
 	acpi_processor_get_throttling_info(pr);
 	acpi_processor_get_limit_info(pr);

drivers/acpi/processor_perflib.c

@@ -240,6 +240,28 @@ void acpi_processor_ppc_exit(void)
 	acpi_processor_ppc_status &= ~PPC_REGISTERED;
 }
 
+/*
+ * Do a quick check if the systems looks like it should use ACPI
+ * cpufreq. We look at a _PCT method being available, but don't
+ * do a whole lot of sanity checks.
+ */
+void acpi_processor_load_module(struct acpi_processor *pr)
+{
+	static int requested;
+	acpi_status status = 0;
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+
+	if (!arch_has_acpi_pdc() || requested)
+		return;
+	status = acpi_evaluate_object(pr->handle, "_PCT", NULL, &buffer);
+	if (!ACPI_FAILURE(status)) {
+		printk(KERN_INFO PREFIX "Requesting acpi_cpufreq\n");
+		request_module_nowait("acpi_cpufreq");
+		requested = 1;
+	}
+	kfree(buffer.pointer);
+}
+
 static int acpi_processor_get_performance_control(struct acpi_processor *pr)
 {
 	int result = 0;

include/acpi/processor.h

@@ -224,6 +224,7 @@ struct acpi_processor_errata {
 	} piix4;
 };
 
+extern void acpi_processor_load_module(struct acpi_processor *pr);
 extern int acpi_processor_preregister_performance(struct
 						  acpi_processor_performance
 						  __percpu *performance);