regulator: Support disabling of unused regulators by machines

At present it is not possible for machine constraints to disable
regulators which have been left on when the system starts, for example
as a result of fixed default configurations in hardware. This means that
power may be wasted by these regulators if they are not in use.

Provide intial support for this with a late_initcall which will disable
any unused regulators if the machine has enabled this feature by calling
regulator_has_full_constraints(). If this has not been called then print
a warning to encourage users to fully specify their constraints so that
we can change this to be the default behaviour in future.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

drivers/regulator/core.c

@@ -28,6 +28,7 @@
 static DEFINE_MUTEX(regulator_list_mutex);
 static LIST_HEAD(regulator_list);
 static LIST_HEAD(regulator_map_list);
+static int has_full_constraints;
 
 /*
  * struct regulator_map
@@ -2142,6 +2143,23 @@ int regulator_suspend_prepare(suspend_state_t state)
 }
 EXPORT_SYMBOL_GPL(regulator_suspend_prepare);
 
+/**
+ * regulator_has_full_constraints - the system has fully specified constraints
+ *
+ * Calling this function will cause the regulator API to disable all
+ * regulators which have a zero use count and don't have an always_on
+ * constraint in a late_initcall.
+ *
+ * The intention is that this will become the default behaviour in a
+ * future kernel release so users are encouraged to use this facility
+ * now.
+ */
+void regulator_has_full_constraints(void)
+{
+	has_full_constraints = 1;
+}
+EXPORT_SYMBOL_GPL(regulator_has_full_constraints);
+
 /**
  * rdev_get_drvdata - get rdev regulator driver data
  * @rdev: regulator
@@ -2209,3 +2227,77 @@ static int __init regulator_init(void)
 
 /* init early to allow our consumers to complete system booting */
 core_initcall(regulator_init);
+
+static int __init regulator_init_complete(void)
+{
+	struct regulator_dev *rdev;
+	struct regulator_ops *ops;
+	struct regulation_constraints *c;
+	int enabled, ret;
+	const char *name;
+
+	mutex_lock(&regulator_list_mutex);
+
+	/* If we have a full configuration then disable any regulators
+	 * which are not in use or always_on.  This will become the
+	 * default behaviour in the future.
+	 */
+	list_for_each_entry(rdev, &regulator_list, list) {
+		ops = rdev->desc->ops;
+		c = rdev->constraints;
+
+		if (c->name)
+			name = c->name;
+		else if (rdev->desc->name)
+			name = rdev->desc->name;
+		else
+			name = "regulator";
+
+		if (!ops->disable || c->always_on)
+			continue;
+
+		mutex_lock(&rdev->mutex);
+
+		if (rdev->use_count)
+			goto unlock;
+
+		/* If we can't read the status assume it's on. */
+		if (ops->is_enabled)
+			enabled = ops->is_enabled(rdev);
+		else
+			enabled = 1;
+
+		if (!enabled)
+			goto unlock;
+
+		if (has_full_constraints) {
+			/* We log since this may kill the system if it
+			 * goes wrong. */
+			printk(KERN_INFO "%s: disabling %s\n",
+			       __func__, name);
+			ret = ops->disable(rdev);
+			if (ret != 0) {
+				printk(KERN_ERR
+				       "%s: couldn't disable %s: %d\n",
+				       __func__, name, ret);
+			}
+		} else {
+			/* The intention is that in future we will
+			 * assume that full constraints are provided
+			 * so warn even if we aren't going to do
+			 * anything here.
+			 */
+			printk(KERN_WARNING
+			       "%s: incomplete constraints, leaving %s on\n",
+			       __func__, name);
+		}
+
+unlock:
+		mutex_unlock(&rdev->mutex);
+	}
+
+	mutex_unlock(&regulator_list_mutex);
+
+	return 0;
+}
+late_initcall(regulator_init_complete);

include/linux/regulator/machine.h

@@ -166,4 +166,6 @@ struct regulator_init_data {
 
 int regulator_suspend_prepare(suspend_state_t state);
 
+void regulator_has_full_constraints(void);
+
 #endif