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.

The patch is based on earlier work by Tobias Jakobi.

Change-Id: I55187da468966b11b27f7d90e1e59471fb602422
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>

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index d03250f9f861cb137beea988cf9099321c6806a7..bb0d84aff15e86822e34fe12e84547c2a7c50da7 100644 (file)
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -275,6 +275,10 @@ 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;
 }
 
@@ -630,6 +634,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
        }
        devfreq->scaling_max_freq = devfreq->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);
@@ -824,14 +831,28 @@ EXPORT_SYMBOL(devm_devfreq_remove_device);
  */
 int devfreq_suspend_device(struct devfreq *devfreq)
 {
+       int ret;
+
        if (!devfreq)
                return -EINVAL;
 
-       if (!devfreq->governor)
-               return 0;
+       if (devfreq->governor) {
+               ret = devfreq->governor->event_handler(devfreq,
+                                       DEVFREQ_GOV_SUSPEND, NULL);
+               if (ret)
+                       return ret;
+       }
+
+       if (devfreq->suspend_freq) {
+               if (atomic_inc_return(&devfreq->suspend_count) > 1)
+                       return 0;
+
+               ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
+               if (ret)
+                       return ret;
+       }
 
-       return devfreq->governor->event_handler(devfreq,
-                               DEVFREQ_GOV_SUSPEND, NULL);
+       return 0;
 }
 EXPORT_SYMBOL(devfreq_suspend_device);
 
@@ -845,14 +866,28 @@ EXPORT_SYMBOL(devfreq_suspend_device);
  */
 int devfreq_resume_device(struct devfreq *devfreq)
 {
+       int ret;
+
        if (!devfreq)
                return -EINVAL;
 
-       if (!devfreq->governor)
-               return 0;
+       if (devfreq->suspend_freq) {
+               if (atomic_dec_return(&devfreq->suspend_count) >= 1)
+                       return 0;
 
-       return devfreq->governor->event_handler(devfreq,
-                               DEVFREQ_GOV_RESUME, NULL);
+               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);
 

diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 3aae5b3af87cf0436d855ff4a355fa1c9b534ce4..0a51aa63853c230dac5c92c3ba67a54b7d5639c3 100644 (file)
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -167,6 +167,10 @@ struct devfreq {
        unsigned long scaling_max_freq;
        bool stop_polling;
 
+       unsigned long suspend_freq;
+       unsigned long resume_freq;
+       atomic_t suspend_count;
+
        /* information for device frequency transition */
        unsigned int total_trans;
        unsigned int *trans_table;