cpuidle/powerpc: Fix smt_snooze_delay functionality.

smt_snooze_delay was designed to  delay idle loop's nap entry
in the native idle code before it got  ported over to use as part of
the cpuidle framework.

A -ve value  assigned to smt_snooze_delay should result in
busy looping, in other words disabling the entry to nap state.

	- https://lists.ozlabs.org/pipermail/linuxppc-dev/2010-May/082450.html

This particular functionality can be achieved currently by
echo 1 > /sys/devices/system/cpu/cpu*/state1/disable
but it is broken when one assigns -ve value to  the smt_snooze_delay
variable either via sysfs entry or ppc64_cpu util.

This patch aims to fix this, by disabling nap state when smt_snooze_delay
variable is set to -ve value.

Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 17 insertions, 7 deletions

diff --git a/arch/powerpc/platforms/pseries/processor_idle.c b/arch/powerpc/platforms/pseries/processor_idle.c
index 02e425aa2af8..a32d56d1f854 100644
--- a/arch/powerpc/platforms/pseries/processor_idle.c
+++ b/arch/powerpc/platforms/pseries/processor_idle.c
@@ -33,13 +33,6 @@ static int max_idle_state = MAX_IDLE_STATE_COUNT - 1;
 static struct cpuidle_device __percpu *pseries_cpuidle_devices;
 static struct cpuidle_state *cpuidle_state_table;
 
-void update_smt_snooze_delay(int snooze)
-{
-        struct cpuidle_driver *drv = cpuidle_get_driver();
-        if (drv)
-                drv->states[0].target_residency = snooze;
-}
-
 static inline void idle_loop_prolog(unsigned long *in_purr, ktime_t *kt_before)
 {
 
@@ -190,6 +183,23 @@ static struct cpuidle_state shared_states[MAX_IDLE_STATE_COUNT] = {
                 .enter = &shared_cede_loop },
 };
 
+void update_smt_snooze_delay(int cpu, int residency)
+{
+        struct cpuidle_driver *drv = cpuidle_get_driver();
+        struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
+
+        if (cpuidle_state_table != dedicated_states)
+                return;
+
+        if (residency < 0) {
+                /* Disable the Nap state on that cpu */
+                if (dev)
+                        dev->states_usage[1].disable = 1;
+        } else
+                if (drv)
+                        drv->states[0].target_residency = residency;
+}
+
 static int pseries_cpuidle_add_cpu_notifier(struct notifier_block *n,
                         unsigned long action, void *hcpu)
 {