From 0c60960d967027309b00e4388d76ce5147c1d385 Mon Sep 17 00:00:00 2001
From: Prashanth Prakash <pprakash@codeaurora.org>
Date: Wed, 15 Nov 2017 10:11:49 -0700
Subject: [PATCH 16/20] cpuidle: Add new macro to enter a retention idle state
Git-commit: db50a74d8193944dd1ee488fd2a813a364fbbaa7
Patch-mainline: v4.16-rc1
References: bsc#1084328
If a CPU is entering a low power idle state where it doesn't lose any
context, then there is no need to call cpu_pm_enter()/cpu_pm_exit().
Add a new macro(CPU_PM_CPU_IDLE_ENTER_RETENTION) to be used by cpuidle
drivers when they are entering retention state. By not calling
cpu_pm_enter and cpu_pm_exit we reduce the latency involved in
entering and exiting the retention idle states.
CPU_PM_CPU_IDLE_ENTER_RETENTION assumes that no state is lost and
hence CPU PM notifiers will not be called. We may need a broader
change if we need to support partial retention states effeciently.
On ARM64 based Qualcomm Server Platform we measured below overhead for
for calling cpu_pm_enter and cpu_pm_exit for retention states.
workload: stress --hdd #CPUs --hdd-bytes 32M -t 30
Average overhead of cpu_pm_enter - 1.2us
Average overhead of cpu_pm_exit - 3.1us
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
include/linux/cpuidle.h | 40 ++++++++++++++++++++++++----------------
1 file changed, 24 insertions(+), 16 deletions(-)
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index fc1e5d7fc1c7..bc80b1540587 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -256,22 +256,30 @@ static inline int cpuidle_register_governor(struct cpuidle_governor *gov)
#define CPUIDLE_DRIVER_STATE_START 0
#endif
-#define CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx) \
-({ \
- int __ret; \
- \
- if (!idx) { \
- cpu_do_idle(); \
- return idx; \
- } \
- \
- __ret = cpu_pm_enter(); \
- if (!__ret) { \
- __ret = low_level_idle_enter(idx); \
- cpu_pm_exit(); \
- } \
- \
- __ret ? -1 : idx; \
+#define __CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx, is_retention) \
+({ \
+ int __ret = 0; \
+ \
+ if (!idx) { \
+ cpu_do_idle(); \
+ return idx; \
+ } \
+ \
+ if (!is_retention) \
+ __ret = cpu_pm_enter(); \
+ if (!__ret) { \
+ __ret = low_level_idle_enter(idx); \
+ if (!is_retention) \
+ cpu_pm_exit(); \
+ } \
+ \
+ __ret ? -1 : idx; \
})
+
+#define CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx) \
+ __CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx, 0)
+
+#define CPU_PM_CPU_IDLE_ENTER_RETENTION(low_level_idle_enter, idx) \
+ __CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx, 1)
#endif /* _LINUX_CPUIDLE_H */
--
2.11.0