[PATCH -v2] cpufreq: skip loading acpi_cpufreq after intel_pstate

[Yinghai Lu <yinghai@kernel.org>]

If the hw support intel_pstate and acpi_cpufreq, intel_pstate will
get loaded first.

acpi_cpufreq_init will call acpi_cpufreq_early_init()
and that will allocate perf data and init those perf data in ACPI core,
(that will cover all cpus). But later it will free them as
cpufreq_register_driver(acpi_cpufreq) will fail as init_pstate is
already registered

Use cpufreq_get_current_driver() to check if we can skip the
acpi_cpufreq loading.

-v2: update changelog and separate second part to another patch, according
     to Viresh.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 drivers/cpufreq/acpi-cpufreq.c |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux-2.6/drivers/cpufreq/acpi-cpufreq.c
===================================================================
--- linux-2.6.orig/drivers/cpufreq/acpi-cpufreq.c
+++ linux-2.6/drivers/cpufreq/acpi-cpufreq.c
@@ -986,6 +986,10 @@ static int __init acpi_cpufreq_init(void
 {
 	int ret;
 
+	/* don't keep reloading if cpufreq_driver exists */
+	if (cpufreq_get_current_driver())
+		return 0;
+
 	if (acpi_disabled)
 		return 0;