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>

1 files changed, 41 insertions, 6 deletions

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index a9fd61bbacf1..46517b61b3a2 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -316,6 +316,10 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
                         "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 @@ struct devfreq *devfreq_add_device(struct device *dev,
         }
         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 @@ EXPORT_SYMBOL(devm_devfreq_remove_device);
  */
 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 @@ EXPORT_SYMBOL(devfreq_suspend_device);
  */
 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);