intel_idle: Add module parameter to prevent ACPI _CST from being used

Add a new module parameter called "no_acpi" to the intel_idle driver
to allow the driver to be prevented from using ACPI _CST via kernel
command line.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index a072b84..26fe383 100644 (file)
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -1138,6 +1138,10 @@ static bool intel_idle_max_cstate_reached(int cstate)
 #ifdef CONFIG_ACPI_PROCESSOR_CSTATE
 #include <acpi/processor.h>
 
+static bool no_acpi __read_mostly;
+module_param(no_acpi, bool, 0444);
+MODULE_PARM_DESC(no_acpi, "Do not use ACPI _CST for building the idle states list");
+
 static struct acpi_processor_power acpi_state_table;
 
 /**
@@ -1167,6 +1171,11 @@ static bool intel_idle_acpi_cst_extract(void)
 {
        unsigned int cpu;
 
+       if (no_acpi) {
+               pr_debug("Not allowed to use ACPI _CST\n");
+               return false;
+       }
+
        for_each_possible_cpu(cpu) {
                struct acpi_processor *pr = per_cpu(processors, cpu);