[PATCH v1] intel_idle: Avoid using deep idle states during initialization

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Commit c0f691388992 ("intel_idle: Use subsys_initcall_sync() for
initialization") effectively made intel_idle initialize earlier which
turns out to interfere with USB EHCI probing on some platforms [1].
Investigation led to the conclusion that this was related to allowing
package idle states to be used earlier than before.

Work around that issue by making intel_idle set a CPU latency QoS
request to prevent package idle states from being used on all platforms
supported by it for the duration of the device_initcall() initialization
phase.

Fixes: c0f691388992 ("intel_idle: Use subsys_initcall_sync() for initialization")
Reported-by: Julian Silver <mendaxca@xxxxxxxxx>
Closes: https://lore.kernel.org/linux-acpi/3353bdf3-4f33-44b1-809b-b0378bee5816@xxxxxxxxx/
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
 drivers/idle/intel_idle.c |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -53,6 +53,7 @@
 #include <linux/notifier.h>
 #include <linux/cpu.h>
 #include <linux/moduleparam.h>
+#include <linux/pm_qos.h>
 #include <linux/sysfs.h>
 #include <asm/cpuid/api.h>
 #include <asm/cpu_device_id.h>
@@ -2822,6 +2823,9 @@ error:
 	pr_info("Failed to adjust C-states with data from 'intel_idle.table'\n");
 }
 
+#define INTEL_IDLE_INIT_QOS	20
+static struct pm_qos_request qos_req __initdata;
+
 static int __init intel_idle_init(void)
 {
 	const struct x86_cpu_id *id;
@@ -2891,6 +2895,13 @@ static int __init intel_idle_init(void)
 	if (retval)
 		pr_warn("failed to initialized sysfs");
 
+	/*
+	 * Some platforms, in particular the Intel S1200BTL motherboard, have a
+	 * problem with using package idle states too early, so prevent that
+	 * from taking place until the device_initcall() phase is over.
+	 */
+	cpu_latency_qos_add_request(&qos_req, INTEL_IDLE_INIT_QOS);
+
 	retval = cpuidle_register_driver(&intel_idle_driver);
 	if (retval) {
 		struct cpuidle_driver *drv = cpuidle_get_driver();
@@ -2915,6 +2926,9 @@ hp_setup_fail:
 	intel_idle_cpuidle_devices_uninit();
 	cpuidle_unregister_driver(&intel_idle_driver);
 init_driver_fail:
+	if (cpu_latency_qos_request_active((&qos_req)))
+		cpu_latency_qos_remove_request(&qos_req);
+
 	intel_idle_sysfs_uninit();
 	free_percpu(intel_idle_cpuidle_devices);
 	return retval;
@@ -2922,6 +2934,15 @@ init_driver_fail:
 }
 subsys_initcall_sync(intel_idle_init);
 
+static int __init intel_idle_init_complete(void)
+{
+	if (cpu_latency_qos_request_active((&qos_req)))
+		cpu_latency_qos_remove_request(&qos_req);
+
+	return 0;
+}
+device_initcall_sync(intel_idle_init_complete);
+
 /*
  * We are not really modular, but we used to support that.  Meaning we also
  * support "intel_idle.max_cstate=..." at boot and also a read-only export of