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Subject[PATCH 3/3] cpuidle/menu: add per cpu pm_qos_resume_latency consideration
Date
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: 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 07e36bb..8d6d25c 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -19,6 +19,7 @@
#include <linux/tick.h>
#include <linux/sched.h>
#include <linux/math64.h>
+#include <linux/cpu.h>

/*
* Please note when changing the tuning values:
@@ -280,17 +281,23 @@ static unsigned int get_typical_interval(struct menu_device *data)
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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