commit 83f8ca45afbf041e312909f442128b99657d90b7
author Lukasz Luba <l.luba@partner.samsung.com> Wed Dec 05 12:05:53 2018 +0100
committer MyungJoo Ham <myungjoo.ham@samsung.com> Tue Dec 11 11:09:47 2018 +0900
tree d9f1ef6d6749aaaa6963cea58747a8024a24f61e
parent 633141721b5bfce7017033a767208af591134b8f

PM / devfreq: add support for suspend/resume of a devfreq device

The patch prepares devfreq device for handling suspend/resume
functionality. The new fields will store needed information during this
process. Devfreq framework handles opp-suspend DT entry and there is no
need of modyfications in the drivers code. It uses atomic variables to
make sure no race condition affects the process.

Suggested-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Suggested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

drivers/devfreq/devfreq.c

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index a9fd61b..46517b6 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -316,6 +316,10 @@
 			"Couldn't update frequency transition information.\n");
 
 	devfreq->previous_freq = new_freq;
+
+	if (devfreq->suspend_freq)
+		devfreq->resume_freq = cur_freq;
+
 	return err;
 }
 
@@ -667,6 +671,9 @@
 	}
 	devfreq->max_freq = devfreq->scaling_max_freq;
 
+	devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
+	atomic_set(&devfreq->suspend_count, 0);
+
 	dev_set_name(&devfreq->dev, "devfreq%d",
 				atomic_inc_return(&devfreq_no));
 	err = device_register(&devfreq->dev);
@@ -867,14 +874,28 @@
  */
 int devfreq_suspend_device(struct devfreq *devfreq)
 {
+	int ret;
+
 	if (!devfreq)
 		return -EINVAL;
 
-	if (!devfreq->governor)
+	if (atomic_inc_return(&devfreq->suspend_count) > 1)
 		return 0;
 
-	return devfreq->governor->event_handler(devfreq,
-				DEVFREQ_GOV_SUSPEND, NULL);
+	if (devfreq->governor) {
+		ret = devfreq->governor->event_handler(devfreq,
+					DEVFREQ_GOV_SUSPEND, NULL);
+		if (ret)
+			return ret;
+	}
+
+	if (devfreq->suspend_freq) {
+		ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL(devfreq_suspend_device);
 
@@ -888,14 +909,28 @@
  */
 int devfreq_resume_device(struct devfreq *devfreq)
 {
+	int ret;
+
 	if (!devfreq)
 		return -EINVAL;
 
-	if (!devfreq->governor)
+	if (atomic_dec_return(&devfreq->suspend_count) >= 1)
 		return 0;
 
-	return devfreq->governor->event_handler(devfreq,
-				DEVFREQ_GOV_RESUME, NULL);
+	if (devfreq->resume_freq) {
+		ret = devfreq_set_target(devfreq, devfreq->resume_freq, 0);
+		if (ret)
+			return ret;
+	}
+
+	if (devfreq->governor) {
+		ret = devfreq->governor->event_handler(devfreq,
+					DEVFREQ_GOV_RESUME, NULL);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL(devfreq_resume_device);