x86/hpet: Simplify CPU online code

The indirection via work scheduled on the upcoming CPU was necessary with the
old hotplug code because the online callback was invoked on the control CPU
not on the upcoming CPU. The rework of the CPU hotplug core guarantees that
the online callbacks are invoked on the upcoming CPU.

Remove the now pointless work redirection.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Link: https://lkml.kernel.org/r/20190623132434.047254075@linutronix.de

arch/x86/kernel/hpet.c

@@ -547,12 +547,10 @@ static int hpet_setup_irq(struct hpet_dev *dev)
 	return 0;
 }
 
-/* This should be called in specific @cpu */
 static void init_one_hpet_msi_clockevent(struct hpet_dev *hdev, int cpu)
 {
 	struct clock_event_device *evt = &hdev->evt;
 
-	WARN_ON(cpu != smp_processor_id());
 	if (!(hdev->flags & HPET_DEV_VALID))
 		return;
 
@@ -684,36 +682,12 @@ static struct hpet_dev *hpet_get_unused_timer(void)
 	return NULL;
 }
 
-struct hpet_work_struct {
-	struct delayed_work work;
-	struct completion complete;
-};
-
-static void hpet_work(struct work_struct *w)
+static int hpet_cpuhp_online(unsigned int cpu)
 {
-	struct hpet_dev *hdev;
-	int cpu = smp_processor_id();
-	struct hpet_work_struct *hpet_work;
+	struct hpet_dev *hdev = hpet_get_unused_timer();
 
-	hpet_work = container_of(w, struct hpet_work_struct, work.work);
-
-	hdev = hpet_get_unused_timer();
 	if (hdev)
 		init_one_hpet_msi_clockevent(hdev, cpu);
-
-	complete(&hpet_work->complete);
-}
-
-static int hpet_cpuhp_online(unsigned int cpu)
-{
-	struct hpet_work_struct work;
-
-	INIT_DELAYED_WORK_ONSTACK(&work.work, hpet_work);
-	init_completion(&work.complete);
-	/* FIXME: add schedule_work_on() */
-	schedule_delayed_work_on(cpu, &work.work, 0);
-	wait_for_completion(&work.complete);
-	destroy_delayed_work_on_stack(&work.work);
 	return 0;
 }
 
@@ -1045,7 +1019,6 @@ static __init int hpet_late_init(void)
 	if (boot_cpu_has(X86_FEATURE_ARAT))
 		return 0;
 
-	/* This notifier should be called after workqueue is ready */
 	ret = cpuhp_setup_state(CPUHP_AP_X86_HPET_ONLINE, "x86/hpet:online",
 				hpet_cpuhp_online, NULL);
 	if (ret)