[PATCH] PM / devfreq: add relation of recommended frequency.

[MyungJoo Ham]

The semantics of "target frequency" given to devfreq driver from
devfreq framework has always been interpretted as "at least" or GLB
(greatest lower bound). However, the framework might want the
device driver to limit its max frequency (LUB: least upper bound),
especially if it is given by thermal framework (it's too hot).

Thus, the target fuction should have another parameter to express
whether the framework wants GLB or LUB. And, the additional parameter,
"u32 options", does it.

With the update, devfreq_recommended_opp() is also updated.

Signed-off-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>

---
Changes from v1
- Style update.
---
 drivers/devfreq/devfreq.c     |   41 ++++++++++++++++++++++++++++++-----------
 drivers/devfreq/exynos4_bus.c |   14 ++++++++++----
 include/linux/devfreq.h       |   16 +++++++++++++---
 3 files changed, 53 insertions(+), 18 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 0b49f59..13794d1 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -84,6 +84,7 @@ int update_devfreq(struct devfreq *devfreq)
 {
 	unsigned long freq;
 	int err = 0;
+	u32 flags = 0;
 
 	if (!mutex_is_locked(&devfreq->lock)) {
 		WARN(true, "devfreq->lock must be locked by the caller.\n");
@@ -104,18 +105,20 @@ int update_devfreq(struct devfreq *devfreq)
 	 * qos_min_freq
 	 */
 
-	if (devfreq->qos_min_freq && freq < devfreq->qos_min_freq)
+	if (devfreq->qos_min_freq && freq < devfreq->qos_min_freq) {
 		freq = devfreq->qos_min_freq;
-	if (devfreq->max_freq && freq > devfreq->max_freq)
+		flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */
+	}
+	if (devfreq->max_freq && freq > devfreq->max_freq) {
 		freq = devfreq->max_freq;
-	if (devfreq->min_freq && freq < devfreq->min_freq)
+		flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
+	}
+	if (devfreq->min_freq && freq < devfreq->min_freq) {
 		freq = devfreq->min_freq;
+		flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */
+	}
 
-	/*
-	 * TODO in the devfreq-next:
-	 * add relation or use rance (freq_min, freq_max)
-	 */
-	err = devfreq->profile->target(devfreq->dev.parent, &freq);
+	err = devfreq->profile->target(devfreq->dev.parent, &freq, flags);
 	if (err)
 		return err;
 
@@ -773,14 +776,30 @@ module_exit(devfreq_exit);
  *			     freq value given to target callback.
  * @dev		The devfreq user device. (parent of devfreq)
  * @freq	The frequency given to target function
+ * @flags	Flags handed from devfreq framework.
  *
  */
-struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq)
+struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq,
+				    u32 flags)
 {
-	struct opp *opp = opp_find_freq_ceil(dev, freq);
+	struct opp *opp;
 
-	if (opp == ERR_PTR(-ENODEV))
+	if (flags & DEVFREQ_FLAG_LEAST_UPPER_BOUND) {
+		/* The freq is an upper bound. opp should be lower */
 		opp = opp_find_freq_floor(dev, freq);
+
+		/* If not available, use the closest opp */
+		if (opp == ERR_PTR(-ENODEV))
+			opp = opp_find_freq_ceil(dev, freq);
+	} else {
+		/* The freq is an lower bound. opp should be higher */
+		opp = opp_find_freq_ceil(dev, freq);
+
+		/* If not available, use the closest opp */
+		if (opp == ERR_PTR(-ENODEV))
+			opp = opp_find_freq_floor(dev, freq);
+	}
+
 	return opp;
 }
 
diff --git a/drivers/devfreq/exynos4_bus.c b/drivers/devfreq/exynos4_bus.c
index 590d686..1a361e9 100644
--- a/drivers/devfreq/exynos4_bus.c
+++ b/drivers/devfreq/exynos4_bus.c
@@ -619,13 +619,19 @@ static int exynos4_bus_setvolt(struct busfreq_data *data, struct opp *opp,
 	return err;
 }
 
-static int exynos4_bus_target(struct device *dev, unsigned long *_freq)
+static int exynos4_bus_target(struct device *dev, unsigned long *_freq,
+			      u32 flags)
 {
 	int err = 0;
-	struct busfreq_data *data = dev_get_drvdata(dev);
-	struct opp *opp = devfreq_recommended_opp(dev, _freq);
-	unsigned long old_freq = opp_get_freq(data->curr_opp);
+	struct platform_device *pdev = container_of(dev, struct platform_device,
+						    dev);
+	struct busfreq_data *data = platform_get_drvdata(pdev);
+	struct opp *opp = devfreq_recommended_opp(dev, _freq, flags);
 	unsigned long freq = opp_get_freq(opp);
+	unsigned long old_freq = opp_get_freq(data->curr_opp);
+
+	if (IS_ERR(opp))
+		return PTR_ERR(opp);
 
 	if (old_freq == freq)
 		return 0;
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index f27d511..85d4b0f 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -59,6 +59,14 @@ struct devfreq_pm_qos_table {
 	s32 qos_value;
 };
 
+/*
+ * The resulting frequency should be at most this. (this bound is the
+ * least upper bound; thus, the resulting freq should be lower or same)
+ * If the flag is not set, the resulting frequency should be at most the
+ * bound (greatest lower bound)
+ */
+#define DEVFREQ_FLAG_LEAST_UPPER_BOUND		0x1
+
 /**
  * struct devfreq_dev_profile - Devfreq's user device profile
  * @initial_freq	The operating frequency when devfreq_add_device() is
@@ -74,6 +82,8 @@ struct devfreq_pm_qos_table {
  *			higher than any operable frequency, set maximum.
  *			Before returning, target function should set
  *			freq at the current frequency.
+ *			The "flags" parameter's possible values are
+ *			explained above with "DEVFREQ_FLAG_*" macros.
  * @get_dev_status	The device should provide the current performance
  *			status to devfreq, which is used by governors.
  * @exit		An optional callback that is called when devfreq
@@ -92,7 +102,7 @@ struct devfreq_dev_profile {
 	int qos_type;
 	struct devfreq_pm_qos_table *qos_list;
 
-	int (*target)(struct device *dev, unsigned long *freq);
+	int (*target)(struct device *dev, unsigned long *freq, u32 flags);
 	int (*get_dev_status)(struct device *dev,
 			      struct devfreq_dev_status *stat);
 	void (*exit)(struct device *dev);
@@ -198,7 +208,7 @@ extern int devfreq_remove_device(struct devfreq *devfreq);
 
 /* Helper functions for devfreq user device driver with OPP. */
 extern struct opp *devfreq_recommended_opp(struct device *dev,
-					   unsigned long *freq);
+					   unsigned long *freq, u32 flags);
 extern int devfreq_register_opp_notifier(struct device *dev,
 					 struct devfreq *devfreq);
 extern int devfreq_unregister_opp_notifier(struct device *dev,
@@ -253,7 +263,7 @@ static int devfreq_remove_device(struct devfreq *devfreq)
 }
 
 static struct opp *devfreq_recommended_opp(struct device *dev,
-					   unsigned long *freq)
+					   unsigned long *freq, u32 flags)
 {
 	return -EINVAL;
 }
-- 
1.7.4.1

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