thermal: intel: hfi: Enable an HFI instance from its first online CPU

Previously, HFI instances were never disabled once enabled. A CPU in an
instance only had to check during boot whether another CPU had previously
initialized the instance and its corresponding data structure.

A subsequent changeset will add functionality to disable instances
to support hibernation. Such change will also make possible to disable an
HFI instance during runtime via CPU hotplug.

Enable an HFI instance from the first of its CPUs that comes online. This
covers the boot, CPU hotplug, and resume-from-suspend cases. It also covers
systems with one or more HFI instances (i.e., packages).
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/thermal/intel/intel_hfi.c

@@ -410,13 +410,12 @@ void intel_hfi_online(unsigned int cpu)
 	/*
 	 * Now check if the HFI instance of the package/die of @cpu has been
 	 * initialized (by checking its header). In such case, all we have to
-	 * do is to add @cpu to this instance's cpumask.
+	 * do is to add @cpu to this instance's cpumask and enable the instance
+	 * if needed.
 	 */
 	mutex_lock(&hfi_instance_lock);
-	if (hfi_instance->hdr) {
-		cpumask_set_cpu(cpu, hfi_instance->cpus);
-		goto unlock;
-	}
+	if (hfi_instance->hdr)
+		goto enable;
 
 	/*
 	 * Hardware is programmed with the physical address of the first page
@@ -442,10 +441,14 @@ void intel_hfi_online(unsigned int cpu)
 	raw_spin_lock_init(&hfi_instance->table_lock);
 	raw_spin_lock_init(&hfi_instance->event_lock);
 
+enable:
 	cpumask_set_cpu(cpu, hfi_instance->cpus);
 
-	hfi_set_hw_table(hfi_instance);
-	hfi_enable();
+	/* Enable this HFI instance if this is its first online CPU. */
+	if (cpumask_weight(hfi_instance->cpus) == 1) {
+		hfi_set_hw_table(hfi_instance);
+		hfi_enable();
+	}
 
 unlock:
 	mutex_unlock(&hfi_instance_lock);