Revert "cpufreq: intel_pstate: Process HWP Guaranteed change notification"

Revert commit d0e936ad ("cpufreq: intel_pstate: Process HWP
Guaranteed change notification"), because it causes a NULL pointer
dereference to occur on Lenovo X1 gen9 laptops due to an HWP
guaranteed performance change interrupt arriving prematurely.

This feature will be revisited in the next cycle.
Reported-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/intel_pstate.c

@@ -32,7 +32,6 @@
 #include <asm/cpu_device_id.h>
 #include <asm/cpufeature.h>
 #include <asm/intel-family.h>
-#include "../drivers/thermal/intel/thermal_interrupt.h"
 
 #define INTEL_PSTATE_SAMPLING_INTERVAL	(10 * NSEC_PER_MSEC)
 
@@ -220,7 +219,6 @@ struct global_params {
  * @sched_flags:	Store scheduler flags for possible cross CPU update
  * @hwp_boost_min:	Last HWP boosted min performance
  * @suspended:		Whether or not the driver has been suspended.
- * @hwp_notify_work:	workqueue for HWP notifications.
  *
  * This structure stores per CPU instance data for all CPUs.
  */
@@ -259,7 +257,6 @@ struct cpudata {
 	unsigned int sched_flags;
 	u32 hwp_boost_min;
 	bool suspended;
-	struct delayed_work hwp_notify_work;
 };
 
 static struct cpudata **all_cpu_data;
@@ -1628,40 +1625,6 @@ static void intel_pstate_sysfs_hide_hwp_dynamic_boost(void)
 
 /************************** sysfs end ************************/
 
-static void intel_pstate_notify_work(struct work_struct *work)
-{
-	mutex_lock(&intel_pstate_driver_lock);
-	cpufreq_update_policy(smp_processor_id());
-	wrmsrl(MSR_HWP_STATUS, 0);
-	mutex_unlock(&intel_pstate_driver_lock);
-}
-
-void notify_hwp_interrupt(void)
-{
-	unsigned int this_cpu = smp_processor_id();
-	struct cpudata *cpudata;
-	u64 value;
-
-	if (!hwp_active || !boot_cpu_has(X86_FEATURE_HWP_NOTIFY))
-		return;
-
-	rdmsrl(MSR_HWP_STATUS, value);
-	if (!(value & 0x01))
-		return;
-
-	cpudata = all_cpu_data[this_cpu];
-	schedule_delayed_work_on(this_cpu, &cpudata->hwp_notify_work, msecs_to_jiffies(10));
-}
-
-static void intel_pstate_enable_hwp_interrupt(struct cpudata *cpudata)
-{
-	/* Enable HWP notification interrupt for guaranteed performance change */
-	if (boot_cpu_has(X86_FEATURE_HWP_NOTIFY)) {
-		INIT_DELAYED_WORK(&cpudata->hwp_notify_work, intel_pstate_notify_work);
-		wrmsrl_on_cpu(cpudata->cpu, MSR_HWP_INTERRUPT, 0x01);
-	}
-}
-
 static void intel_pstate_hwp_enable(struct cpudata *cpudata)
 {
 	/* First disable HWP notification interrupt as we don't process them */
@@ -1671,8 +1634,6 @@ static void intel_pstate_hwp_enable(struct cpudata *cpudata)
 	wrmsrl_on_cpu(cpudata->cpu, MSR_PM_ENABLE, 0x1);
 	if (cpudata->epp_default == -EINVAL)
 		cpudata->epp_default = intel_pstate_get_epp(cpudata, 0);
-
-	intel_pstate_enable_hwp_interrupt(cpudata);
 }
 
 static int atom_get_min_pstate(void)