linux-kernel - [PATCH 4/6] devfreq: add devfreq

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Date:   Wed, 21 Nov 2018 19:01:39 +0100
From:   Lukasz Luba <l.luba@...tner.samsung.com>
To:     linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org
Cc:     tjakobi@...h.uni-bielefeld.de, myungjoo.ham@...sung.com,
        kyungmin.park@...sung.com, cw00.choi@...sung.com,
        rjw@...ysocki.net, len.brown@...el.com, pavel@....cz,
        gregkh@...uxfoundation.org, keescook@...omium.org,
        anton@...msg.org, ccross@...roid.com, tony.luck@...el.com,
        robh+dt@...nel.org, mark.rutland@....com, kgene@...nel.org,
        krzk@...nel.org, m.szyprowski@...sung.com,
        b.zolnierkie@...sung.com, Lukasz Luba <l.luba@...tner.samsung.com>
Subject: [PATCH 4/6] devfreq: add devfreq_suspend/resume() functions

This patch adds implementation for global suspend/resume for
devfreq framework. System suspend will next use these functions.

The patch draws on Tobias Jakobi's work posted ~2 years ago, who tried to
solve issue with devfreq device's frequency during suspend/resume.
During the discussion on LKML some corner cases and comments appeared
related to the design. This patch address them keeping in mind suggestions
from Chanwoo Choi.

Suggested-by: Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>
Suggested-by: Chanwoo Choi <cw00.choi@...sung.com>
Signed-off-by: Lukasz Luba <l.luba@...tner.samsung.com>
---
 drivers/devfreq/devfreq.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/devfreq.h   |  7 +++++++
 2 files changed, 56 insertions(+)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 7e09de8..2f4391c 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -44,6 +44,9 @@ static LIST_HEAD(devfreq_governor_list);
 static LIST_HEAD(devfreq_list);
 static DEFINE_MUTEX(devfreq_list_lock);
 
+/* Flag showing state of suspend/resume */
+static bool devfreq_suspended;
+
 /**
  * find_device_devfreq() - find devfreq struct using device pointer
  * @dev:	device pointer used to lookup device devfreq.
@@ -938,6 +941,52 @@ int devfreq_resume_device(struct devfreq *devfreq)
 EXPORT_SYMBOL(devfreq_resume_device);
 
 /**
+ * devfreq_suspend() - Suspend devfreq governors and devices
+ *
+ * Called during system wide Suspend/Hibernate cycles for suspending governors
+ * and devices preserving the state for resume. On some platforms the devfreq
+ * device must have precise state (frequency) after resume in order to provide
+ * fully operating setup.
+ */
+void devfreq_suspend(void)
+{
+	struct devfreq *devfreq;
+	int ret;
+
+	mutex_lock(&devfreq_list_lock);
+	list_for_each_entry(devfreq, &devfreq_list, node) {
+		ret = devfreq_suspend_device(devfreq);
+		if (ret)
+			dev_warn(&devfreq->dev, "device suspend failed\n");
+	}
+	mutex_unlock(&devfreq_list_lock);
+
+	devfreq_suspended = true;
+}
+
+/**
+ * devfreq_resume() - Resume devfreq governors and devices
+ *
+ * Called during system wide Suspend/Hibernate cycle for resuming governors and
+ * devices that are suspended with devfreq_suspend().
+ */
+void devfreq_resume(void)
+{
+	struct devfreq *devfreq;
+	int ret;
+
+	devfreq_suspended = false;
+
+	mutex_lock(&devfreq_list_lock);
+	list_for_each_entry(devfreq, &devfreq_list, node) {
+		ret = devfreq_resume_device(devfreq);
+		if (ret)
+			dev_warn(&devfreq->dev, "device resume failed\n");
+	}
+	mutex_unlock(&devfreq_list_lock);
+}
+
+/**
  * devfreq_add_governor() - Add devfreq governor
  * @governor:	the devfreq governor to be added
  */
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 7fe96f9..4f0fea8 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -202,6 +202,10 @@ extern void devm_devfreq_remove_device(struct device *dev,
 extern int devfreq_suspend_device(struct devfreq *devfreq);
 extern int devfreq_resume_device(struct devfreq *devfreq);
 
+
+extern void devfreq_suspend(void);
+extern void devfreq_resume(void);
+
 /**
  * update_devfreq() - Reevaluate the device and configure frequency
  * @devfreq:	the devfreq device
@@ -396,6 +400,9 @@ static inline int devfreq_update_stats(struct devfreq *df)
 {
 	return -EINVAL;
 }
+
+static inline void devfreq_suspend(void) {}
+static inline void devfreq_resume(void) {}
 #endif /* CONFIG_PM_DEVFREQ */
 
 #endif /* __LINUX_DEVFREQ_H__ */
-- 
2.7.4