From 4ec32d9e8e5b6d6eb491eeee3938665d8a2388fa Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Fri, 13 Dec 2019 09:56:29 +0100
Subject: [PATCH] intel_idle: Add module parameter to prevent ACPI _CST from being used
Git-commit: 4ec32d9e8e5b6d6eb491eeee3938665d8a2388fa
Patch-mainline: v5.6-rc1
References: jsc#SLE-12679

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/idle/intel_idle.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index a072b84d9595..26fe383bb921 100644
--- 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);
 
-- 
2.16.4