PM / QoS: CPU C-state breakage with PM Qos change

Looks like change "PM QoS: Move and rename the implementation files"
merged during the 3.2 development cycle made PM QoS depend on
CONFIG_PM which depends on (PM_SLEEP || PM_RUNTIME).

That breaks CPU C-states with kernels not having these CONFIGs, causing CPUs
to spend time in Polling loop idle instead of going into deep C-states,
consuming way way more power. This is with either acpi idle or intel idle
enabled.

Either CONFIG_PM should be enabled with any pm_qos users or
the !CONFIG_PM pm_qos_request() should return sane defaults not to break
the existing users. Here's is the patch for the latter option.

[rjw: Modified the changelog slightly.]

Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: stable@vger.kernel.org

diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
index e5bbcba..4d99e4e 100644 (file)
--- a/include/linux/pm_qos.h
+++ b/include/linux/pm_qos.h
@@ -110,7 +110,19 @@ static inline void pm_qos_remove_request(struct pm_qos_request *req)
                        { return; }
 
 static inline int pm_qos_request(int pm_qos_class)
-                       { return 0; }
+{
+       switch (pm_qos_class) {
+       case PM_QOS_CPU_DMA_LATENCY:
+               return PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE;
+       case PM_QOS_NETWORK_LATENCY:
+               return PM_QOS_NETWORK_LAT_DEFAULT_VALUE;
+       case PM_QOS_NETWORK_THROUGHPUT:
+               return PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE;
+       default:
+               return PM_QOS_DEFAULT_VALUE;
+       }
+}
+
 static inline int pm_qos_add_notifier(int pm_qos_class,
                                      struct notifier_block *notifier)
                        { return 0; }