linux-kernel - [PATCH 2/4] cpu: expose pm_qos_resume

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1471595114-1688-2-git-send-email-alex.shi@linaro.org>
Date:   Fri, 19 Aug 2016 16:25:12 +0800
From:   Alex Shi <alex.shi@...aro.org>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 2/4] cpu: expose pm_qos_resume_latency for each cpu

The cpu-dma PM QoS constraint impacts all the cpus in the system. There
is no way to let the user to choose a PM QoS constraint per cpu.

The following patch exposes to the userspace a per cpu based sysfs file
in order to let the userspace to change the value of the PM QoS latency
constraint.

This change is inoperative in its form and the cpuidle governors have to
take into account the per cpu latency constraint in addition to the
global cpu-dma latency constraint in order to operate properly.

BTW
The pm_qos_resume_latency usage defined in
Documentation/ABI/testing/sysfs-devices-power
The /sys/devices/.../power/pm_qos_resume_latency_us attribute
contains the PM QoS resume latency limit for the given device,
which is the maximum allowed time it can take to resume the
device, after it has been suspended at run time, from a resume
request to the moment the device will be ready to process I/O,
in microseconds.  If it is equal to 0, however, this means that
the PM QoS resume latency may be arbitrary.

Signed-off-by: Alex Shi <alex.shi@...aro.org>
To: linux-kernel@...r.kernel.org
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 drivers/base/cpu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 4c28e1a..2c3b359 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -17,6 +17,7 @@
 #include <linux/of.h>
 #include <linux/cpufeature.h>
 #include <linux/tick.h>
+#include <linux/pm_qos.h>

 #include "base.h"

@@ -376,6 +377,7 @@ int register_cpu(struct cpu *cpu, int num)

 	per_cpu(cpu_sys_devices, num) = &cpu->dev;
 	register_cpu_under_node(num, cpu_to_node(num));
+	dev_pm_qos_expose_latency_limit(&cpu->dev, 0);

 	return 0;
 }
-- 
2.8.1.101.g72d917a