ACPI / cpuidle: fix max idle state handling with hotplug CPU support

acpi_processor_hotplug() calls acpi_processor_setup_cpuidle_cx()
without calling acpi_processor_setup_cpuidle_states() first so it
is possible that dev->state_count becomes different from
drv->state_count (in case of SMP system with unsupported C2/C3
states + enabled CPU hotplug and num_online_cpus() becoming > 1).

The driver code assumes that cpuidle core will handle such cases
but currently this is untrue (dev->state_count is used only for
handling cpuidle state sysfs entries and drv->state_count is used
for all other cases) and will not be fixed in the future as
dev->state_count is planned to be removed.

Fix the issue by checking for the max supported idle state in
C2/C3 state's ->enter handler (acpi_idle_enter_simple() for C2/C3
and acpi_idle_enter_bm() for C3 + bm_check flag set) and setting
the C1 state (instead of higher states) when needed.

Also remove no longer needed max idle state checks from
acpi_processor_setup_cpuidle_[states,cx]().

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/processor_idle.c

@@ -785,6 +785,13 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
 	if (unlikely(!pr))
 		return -EINVAL;
 
+#ifdef CONFIG_HOTPLUG_CPU
+	if ((cx->type != ACPI_STATE_C1) && (num_online_cpus() > 1) &&
+	    !pr->flags.has_cst &&
+	    !(acpi_gbl_FADT.flags & ACPI_FADT_C2_MP_SUPPORTED))
+		return acpi_idle_enter_c1(dev, drv, CPUIDLE_DRIVER_STATE_START);
+#endif
+
 	if (cx->entry_method == ACPI_CSTATE_FFH) {
 		if (current_set_polling_and_test())
 			return -EINVAL;
@@ -831,6 +838,13 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
 	if (unlikely(!pr))
 		return -EINVAL;
 
+#ifdef CONFIG_HOTPLUG_CPU
+	if ((cx->type != ACPI_STATE_C1) && (num_online_cpus() > 1) &&
+	    !pr->flags.has_cst &&
+	    !(acpi_gbl_FADT.flags & ACPI_FADT_C2_MP_SUPPORTED))
+		return acpi_idle_enter_c1(dev, drv, CPUIDLE_DRIVER_STATE_START);
+#endif
+
 	if (!cx->bm_sts_skip && acpi_idle_bm_check()) {
 		if (drv->safe_state_index >= 0) {
 			return drv->states[drv->safe_state_index].enter(dev,
@@ -932,12 +946,6 @@ static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
 		if (!cx->valid)
 			continue;
 
-#ifdef CONFIG_HOTPLUG_CPU
-		if ((cx->type != ACPI_STATE_C1) && (num_online_cpus() > 1) &&
-		    !pr->flags.has_cst &&
-		    !(acpi_gbl_FADT.flags & ACPI_FADT_C2_MP_SUPPORTED))
-			continue;
-#endif
 		per_cpu(acpi_cstate[count], dev->cpu) = cx;
 
 		count++;
@@ -987,13 +995,6 @@ static int acpi_processor_setup_cpuidle_states(struct acpi_processor *pr)
 		if (!cx->valid)
 			continue;
 
-#ifdef CONFIG_HOTPLUG_CPU
-		if ((cx->type != ACPI_STATE_C1) && (num_online_cpus() > 1) &&
-		    !pr->flags.has_cst &&
-		    !(acpi_gbl_FADT.flags & ACPI_FADT_C2_MP_SUPPORTED))
-			continue;
-#endif
-
 		state = &drv->states[count];
 		snprintf(state->name, CPUIDLE_NAME_LEN, "C%d", i);
 		strncpy(state->desc, cx->desc, CPUIDLE_DESC_LEN);