acpi: Export the acpi_processor_get_performance_info

The git commit d5aaffa9
(cpufreq: handle cpufreq being disabled for all exported function)
tightens the cpufreq API by returning errors when disable_cpufreq()
had been called.

The problem we are hitting is that the module xen-acpi-processor which
uses the ACPI's functions: acpi_processor_register_performance,
acpi_processor_preregister_performance, and acpi_processor_notify_smm
fails at acpi_processor_register_performance with -22.

Note that earlier during bootup in arch/x86/xen/setup.c there is also
an call to cpufreq's API: disable_cpufreq().

This is b/c we want the Linux kernel to parse the ACPI data, but leave
the cpufreq decisions to the hypervisor.

In v3.9 all the checks that d5aaffa9
added are now hit and the calls to cpufreq_register_notifier will now
fail. This means that acpi_processor_ppc_init ends up printing:

"Warning: Processor Platform Limit not supported"

and the acpi_processor_ppc_status is not set.

The repercussions of that is that the call to
acpi_processor_register_performance fails right away at:

	if (!(acpi_processor_ppc_status & PPC_REGISTERED))

and we don't progress any further on parsing and extracting the _P*
objects.

The only reason the Xen code called that function was b/c it was
exported and the only way to gather the P-states. But we can also
just make acpi_processor_get_performance_info be exported and not
use acpi_processor_register_performance. This patch does so.
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/acpi/processor_perflib.c

@@ -465,7 +465,7 @@ static int acpi_processor_get_performance_states(struct acpi_processor *pr)
 	return result;
 }
 
-static int acpi_processor_get_performance_info(struct acpi_processor *pr)
+int acpi_processor_get_performance_info(struct acpi_processor *pr)
 {
 	int result = 0;
 	acpi_status status = AE_OK;
@@ -509,7 +509,7 @@ static int acpi_processor_get_performance_info(struct acpi_processor *pr)
 #endif
 	return result;
 }
-
+EXPORT_SYMBOL_GPL(acpi_processor_get_performance_info);
 int acpi_processor_notify_smm(struct module *calling_module)
 {
 	acpi_status status;

drivers/xen/xen-acpi-processor.c

@@ -500,16 +500,16 @@ static int __init xen_acpi_processor_init(void)
 	(void)acpi_processor_preregister_performance(acpi_perf_data);
 
 	for_each_possible_cpu(i) {
+		struct acpi_processor *pr;
 		struct acpi_processor_performance *perf;
 
+		pr = per_cpu(processors, i);
 		perf = per_cpu_ptr(acpi_perf_data, i);
-		rc = acpi_processor_register_performance(perf, i);
+		pr->performance = perf;
+		rc = acpi_processor_get_performance_info(pr);
 		if (rc)
 			goto err_out;
 	}
-	rc = acpi_processor_notify_smm(THIS_MODULE);
-	if (rc)
-		goto err_unregister;
 
 	for_each_possible_cpu(i) {
 		struct acpi_processor *_pr;

include/acpi/processor.h

@@ -235,6 +235,9 @@ extern void acpi_processor_unregister_performance(struct
          if a _PPC object exists, rmmod is disallowed then */
 int acpi_processor_notify_smm(struct module *calling_module);
 
+/* parsing the _P* objects. */
+extern int acpi_processor_get_performance_info(struct acpi_processor *pr);
+
 /* for communication between multiple parts of the processor kernel module */
 DECLARE_PER_CPU(struct acpi_processor *, processors);
 extern struct acpi_processor_errata errata;