PM / OPP: Allow platform specific custom set_opp() callbacks

The generic set_opp() handler isn't sufficient for platforms with
complex DVFS.  For example, some TI platforms have multiple regulators
for a CPU device. The order in which various supplies need to be
programmed is only known to the platform code and its best to leave it
to it.

This patch implements APIs to register platform specific set_opp()
callback.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Dave Gerlach <d-gerlach@ti.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/opp/core.c

@@ -687,6 +687,7 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
 {
 	struct opp_table *opp_table;
 	unsigned long freq, old_freq;
+	int (*set_opp)(struct dev_pm_set_opp_data *data);
 	struct dev_pm_opp *old_opp, *opp;
 	struct regulator **regulators;
 	struct dev_pm_set_opp_data *data;
@@ -751,6 +752,11 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
 		return _generic_set_opp_clk_only(dev, clk, old_freq, freq);
 	}
 
+	if (opp_table->set_opp)
+		set_opp = opp_table->set_opp;
+	else
+		set_opp = _generic_set_opp;
+
 	data = opp_table->set_opp_data;
 	data->regulators = regulators;
 	data->regulator_count = opp_table->regulator_count;
@@ -769,7 +775,7 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
 
 	rcu_read_unlock();
 
-	return _generic_set_opp(data);
+	return set_opp(data);
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_set_rate);
 
@@ -903,6 +909,9 @@ static void _remove_opp_table(struct opp_table *opp_table)
 	if (opp_table->regulators)
 		return;
 
+	if (opp_table->set_opp)
+		return;
+
 	/* Release clk */
 	if (!IS_ERR(opp_table->clk))
 		clk_put(opp_table->clk);
@@ -1569,6 +1578,109 @@ unlock:
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_put_regulators);
 
+/**
+ * dev_pm_opp_register_set_opp_helper() - Register custom set OPP helper
+ * @dev: Device for which the helper is getting registered.
+ * @set_opp: Custom set OPP helper.
+ *
+ * This is useful to support complex platforms (like platforms with multiple
+ * regulators per device), instead of the generic OPP set rate helper.
+ *
+ * This must be called before any OPPs are initialized for the device.
+ *
+ * Locking: The internal opp_table and opp structures are RCU protected.
+ * Hence this function internally uses RCU updater strategy with mutex locks
+ * to keep the integrity of the internal data structures. Callers should ensure
+ * that this function is *NOT* called under RCU protection or in contexts where
+ * mutex cannot be locked.
+ */
+int dev_pm_opp_register_set_opp_helper(struct device *dev,
+			int (*set_opp)(struct dev_pm_set_opp_data *data))
+{
+	struct opp_table *opp_table;
+	int ret;
+
+	if (!set_opp)
+		return -EINVAL;
+
+	mutex_lock(&opp_table_lock);
+
+	opp_table = _add_opp_table(dev);
+	if (!opp_table) {
+		ret = -ENOMEM;
+		goto unlock;
+	}
+
+	/* This should be called before OPPs are initialized */
+	if (WARN_ON(!list_empty(&opp_table->opp_list))) {
+		ret = -EBUSY;
+		goto err;
+	}
+
+	/* Already have custom set_opp helper */
+	if (WARN_ON(opp_table->set_opp)) {
+		ret = -EBUSY;
+		goto err;
+	}
+
+	opp_table->set_opp = set_opp;
+
+	mutex_unlock(&opp_table_lock);
+	return 0;
+
+err:
+	_remove_opp_table(opp_table);
+unlock:
+	mutex_unlock(&opp_table_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_register_set_opp_helper);
+
+/**
+ * dev_pm_opp_register_put_opp_helper() - Releases resources blocked for
+ *					   set_opp helper
+ * @dev: Device for which custom set_opp helper has to be cleared.
+ *
+ * Locking: The internal opp_table and opp structures are RCU protected.
+ * Hence this function internally uses RCU updater strategy with mutex locks
+ * to keep the integrity of the internal data structures. Callers should ensure
+ * that this function is *NOT* called under RCU protection or in contexts where
+ * mutex cannot be locked.
+ */
+void dev_pm_opp_register_put_opp_helper(struct device *dev)
+{
+	struct opp_table *opp_table;
+
+	mutex_lock(&opp_table_lock);
+
+	/* Check for existing table for 'dev' first */
+	opp_table = _find_opp_table(dev);
+	if (IS_ERR(opp_table)) {
+		dev_err(dev, "Failed to find opp_table: %ld\n",
+			PTR_ERR(opp_table));
+		goto unlock;
+	}
+
+	if (!opp_table->set_opp) {
+		dev_err(dev, "%s: Doesn't have custom set_opp helper set\n",
+			__func__);
+		goto unlock;
+	}
+
+	/* Make sure there are no concurrent readers while updating opp_table */
+	WARN_ON(!list_empty(&opp_table->opp_list));
+
+	opp_table->set_opp = NULL;
+
+	/* Try freeing opp_table if this was the last blocking resource */
+	_remove_opp_table(opp_table);
+
+unlock:
+	mutex_unlock(&opp_table_lock);
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_register_put_opp_helper);
+
 /**
  * dev_pm_opp_add()  - Add an OPP table from a table definitions
  * @dev:	device for which we do this operation

drivers/base/power/opp/opp.h

@@ -141,6 +141,7 @@ enum opp_table_access {
  * @clk: Device's clock handle
  * @regulators: Supply regulators
  * @regulator_count: Number of power supply regulators
+ * @set_opp: Platform specific set_opp callback
  * @set_opp_data: Data to be passed to set_opp callback
  * @dentry:	debugfs dentry pointer of the real device directory (not links).
  * @dentry_name: Name of the real dentry.
@@ -179,6 +180,7 @@ struct opp_table {
 	struct regulator **regulators;
 	unsigned int regulator_count;
 
+	int (*set_opp)(struct dev_pm_set_opp_data *data);
 	struct dev_pm_set_opp_data *set_opp_data;
 
 #ifdef CONFIG_DEBUG_FS

include/linux/pm_opp.h

@@ -116,6 +116,8 @@ int dev_pm_opp_set_prop_name(struct device *dev, const char *name);
 void dev_pm_opp_put_prop_name(struct device *dev);
 struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[], unsigned int count);
 void dev_pm_opp_put_regulators(struct opp_table *opp_table);
+int dev_pm_opp_register_set_opp_helper(struct device *dev, int (*set_opp)(struct dev_pm_set_opp_data *data));
+void dev_pm_opp_register_put_opp_helper(struct device *dev);
 int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq);
 int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, const struct cpumask *cpumask);
 int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask);
@@ -215,6 +217,14 @@ static inline int dev_pm_opp_set_supported_hw(struct device *dev,
 
 static inline void dev_pm_opp_put_supported_hw(struct device *dev) {}
 
+static inline int dev_pm_opp_register_set_opp_helper(struct device *dev,
+			int (*set_opp)(struct dev_pm_set_opp_data *data))
+{
+	return -ENOTSUPP;
+}
+
+static inline void dev_pm_opp_register_put_opp_helper(struct device *dev) {}
+
 static inline int dev_pm_opp_set_prop_name(struct device *dev, const char *name)
 {
 	return -ENOTSUPP;