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[PATCH 4/4] cpuidle/menu: add per cpu pm_qos_resume_latency consideration

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  [PATCH 4/4] cpuidle/menu: add per cpu pm_qos_resume_latency consideration Alex Shi <alex.shi@linaro.org> - 2016-08-25 10:50 +0200

#1469977 — [PATCH 4/4] cpuidle/menu: add per cpu pm_qos_resume_latency consideration

Kernel or user may have special requirement on cpu response time, like
if a interrupt is pinned to a cpu, we don't want the cpu goes too deep
sleep. This patch can prevent this thing happen by consider per cpu
resume_latency setting in cpu sleep state selection in menu governor.

The pm_qos_resume_latency ask device to give reponse in this time. That's
similar with cpu cstates' entry_latency + exit_latency. But since
most of cpu cstate either has no entry_latency or add it into exit_latency
So, we just can restrict this time requirement as states exit_latency.

The 0 value of pm_qos_resume_latency is for no limitation according ABI
definition. So set the value 1 could get the 0 latency if it's needed.

Signed-off-by: Alex Shi <alex.shi@linaro.org>
To: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Alex Shi <alex.shi@linaro.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
---
 drivers/cpuidle/governors/menu.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index bb58e2a..e354880 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -12,6 +12,7 @@
 
 #include <linux/kernel.h>
 #include <linux/cpuidle.h>
+#include <linux/cpu.h>
 #include <linux/pm_qos.h>
 #include <linux/time.h>
 #include <linux/ktime.h>
@@ -281,17 +282,23 @@ again:
 static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 {
 	struct menu_device *data = this_cpu_ptr(&menu_devices);
+	struct device *device = get_cpu_device(dev->cpu);
 	int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
 	int i;
 	unsigned int interactivity_req;
 	unsigned int expected_interval;
 	unsigned long nr_iowaiters, cpu_load;
+	int resume_latency = dev_pm_qos_read_value(device);
 
 	if (data->needs_update) {
 		menu_update(drv, dev);
 		data->needs_update = 0;
 	}
 
+	/* resume_latency is 0 means no restriction */
+	if (resume_latency && resume_latency < latency_req)
+		latency_req = resume_latency;
+
 	/* Special case when user has set very strict latency requirement */
 	if (unlikely(latency_req == 0))
 		return 0;
-- 
2.8.1.101.g72d917a

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