regulator: core: Change voltage setting path

On Odroid XU3/4 and other Exynos5422 based boards there is a case, that
different devices on the board are supplied by different regulators
with non-fixed voltages. If one of these devices temporarily requires
higher voltage, there might occur a situation that the spread between
two devices' voltages is so high, that there is a risk of changing
'high' and 'low' states on the interconnection between devices powered
by those regulators.

Uncoupled regulators should be a special case of coupled regulators, so
they should share a common voltage setting path. When enabling,
disabling or setting voltage of a coupled regulator, all coupled
regulators should be locked. Regulator's supplies should be locked, when
setting voltage of a single regulator. Enabling a coupled regulator or
setting its voltage should not be possible if some of its coupled
regulators, has not been registered.

Add function for locking coupled regulators and supplies. Extract
a new function regulator_set_voltage_rdev() from
regulator_set_voltage_unlocked(), which is called when setting
voltage of a single regulator.
Signed-off-by: Maciej Purski <m.purski@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -107,6 +107,9 @@ static int _regulator_do_set_voltage(struct regulator_dev *rdev,
 				     int min_uV, int max_uV);
 static int regulator_balance_voltage(struct regulator_dev *rdev,
 				     suspend_state_t state);
+static int regulator_set_voltage_rdev(struct regulator_dev *rdev,
+				      int min_uV, int max_uV,
+				      suspend_state_t state);
 static struct regulator *create_regulator(struct regulator_dev *rdev,
 					  struct device *dev,
 					  const char *supply_name);
@@ -198,37 +201,66 @@ static void regulator_unlock(struct regulator_dev *rdev)
 	}
 }
 
-/**
- * regulator_lock_supply - lock a regulator and its supplies
- * @rdev:         regulator source
- */
-static void regulator_lock_supply(struct regulator_dev *rdev)
+static int regulator_lock_recursive(struct regulator_dev *rdev,
+				    unsigned int subclass)
 {
+	struct regulator_dev *c_rdev;
 	int i;
 
-	for (i = 0; rdev; rdev = rdev_get_supply(rdev), i++)
-		regulator_lock_nested(rdev, i);
+	for (i = 0; i < rdev->coupling_desc.n_coupled; i++) {
+		c_rdev = rdev->coupling_desc.coupled_rdevs[i];
+
+		if (!c_rdev)
+			continue;
+
+		regulator_lock_nested(c_rdev, subclass++);
+
+		if (c_rdev->supply)
+			subclass =
+				regulator_lock_recursive(c_rdev->supply->rdev,
+							 subclass);
+	}
+
+	return subclass;
 }
 
 /**
- * regulator_unlock_supply - unlock a regulator and its supplies
- * @rdev:         regulator source
+ * regulator_unlock_dependent - unlock regulator's suppliers and coupled
+ *				regulators
+ * @rdev:			regulator source
+ *
+ * Unlock all regulators related with rdev by coupling or suppling.
  */
-static void regulator_unlock_supply(struct regulator_dev *rdev)
+static void regulator_unlock_dependent(struct regulator_dev *rdev)
 {
-	struct regulator *supply;
+	struct regulator_dev *c_rdev;
+	int i;
 
-	while (1) {
-		regulator_unlock(rdev);
-		supply = rdev->supply;
+	for (i = 0; i < rdev->coupling_desc.n_coupled; i++) {
+		c_rdev = rdev->coupling_desc.coupled_rdevs[i];
 
-		if (!rdev->supply)
-			return;
+		if (!c_rdev)
+			continue;
+
+		regulator_unlock(c_rdev);
 
-		rdev = supply->rdev;
+		if (c_rdev->supply)
+			regulator_unlock_dependent(c_rdev->supply->rdev);
 	}
 }
 
+/**
+ * regulator_lock_dependent - lock regulator's suppliers and coupled regulators
+ * @rdev:			regulator source
+ *
+ * This function as a wrapper on regulator_lock_recursive(), which locks
+ * all regulators related with rdev by coupling or suppling.
+ */
+static inline void regulator_lock_dependent(struct regulator_dev *rdev)
+{
+	regulator_lock_recursive(rdev, 0);
+}
+
 /**
  * of_get_regulator - get a regulator device node based on supply name
  * @dev: Device pointer for the consumer (of regulator) device
@@ -2261,6 +2293,11 @@ int regulator_enable(struct regulator *regulator)
 	struct regulator_dev *rdev = regulator->rdev;
 	int ret = 0;
 
+	if (rdev->coupling_desc.n_resolved != rdev->coupling_desc.n_coupled) {
+		rdev_err(rdev, "not all coupled regulators registered\n");
+		return -EPERM;
+	}
+
 	if (regulator->always_on)
 		return 0;
 
@@ -2270,9 +2307,12 @@ int regulator_enable(struct regulator *regulator)
 			return ret;
 	}
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock_dependent(rdev);
 	ret = _regulator_enable(rdev);
-	mutex_unlock(&rdev->mutex);
+	/* balance only if there are regulators coupled */
+	if (rdev->coupling_desc.n_coupled > 1)
+		regulator_balance_voltage(rdev, PM_SUSPEND_ON);
+	regulator_unlock_dependent(rdev);
 
 	if (ret != 0 && rdev->supply)
 		regulator_disable(rdev->supply);
@@ -2378,9 +2418,11 @@ int regulator_disable(struct regulator *regulator)
 	if (regulator->always_on)
 		return 0;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock_dependent(rdev);
 	ret = _regulator_disable(rdev);
-	mutex_unlock(&rdev->mutex);
+	if (rdev->coupling_desc.n_coupled > 1)
+		regulator_balance_voltage(rdev, PM_SUSPEND_ON);
+	regulator_unlock_dependent(rdev);
 
 	if (ret == 0 && rdev->supply)
 		regulator_disable(rdev->supply);
@@ -2429,10 +2471,12 @@ int regulator_force_disable(struct regulator *regulator)
 	struct regulator_dev *rdev = regulator->rdev;
 	int ret;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock_dependent(rdev);
 	regulator->uA_load = 0;
 	ret = _regulator_force_disable(regulator->rdev);
-	mutex_unlock(&rdev->mutex);
+	if (rdev->coupling_desc.n_coupled > 1)
+		regulator_balance_voltage(rdev, PM_SUSPEND_ON);
+	regulator_unlock_dependent(rdev);
 
 	if (rdev->supply)
 		while (rdev->open_count--)
@@ -2580,9 +2624,9 @@ int regulator_is_enabled(struct regulator *regulator)
 	if (regulator->always_on)
 		return 1;
 
-	mutex_lock(&regulator->rdev->mutex);
+	regulator_lock_dependent(regulator->rdev);
 	ret = _regulator_is_enabled(regulator->rdev);
-	mutex_unlock(&regulator->rdev->mutex);
+	regulator_unlock_dependent(regulator->rdev);
 
 	return ret;
 }
@@ -2991,8 +3035,12 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
 	int ret = 0;
 	int old_min_uV, old_max_uV;
 	int current_uV;
-	int best_supply_uV = 0;
-	int supply_change_uV = 0;
+
+	if (rdev->coupling_desc.n_resolved != rdev->coupling_desc.n_coupled) {
+		rdev_err(rdev, "not all coupled regulators registered\n");
+		ret = -EPERM;
+		goto out;
+	}
 
 	/* If we're setting the same range as last time the change
 	 * should be a noop (some cpufreq implementations use the same
@@ -3036,6 +3084,27 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
 	if (ret < 0)
 		goto out2;
 
+	/* for not coupled regulators this will just set the voltage */
+	ret = regulator_balance_voltage(rdev, state);
+	if (ret < 0)
+		goto out2;
+
+out:
+	return 0;
+out2:
+	voltage->min_uV = old_min_uV;
+	voltage->max_uV = old_max_uV;
+
+	return ret;
+}
+
+static int regulator_set_voltage_rdev(struct regulator_dev *rdev, int min_uV,
+				      int max_uV, suspend_state_t state)
+{
+	int best_supply_uV = 0;
+	int supply_change_uV = 0;
+	int ret;
+
 	if (rdev->supply &&
 	    regulator_ops_is_valid(rdev->supply->rdev,
 				   REGULATOR_CHANGE_VOLTAGE) &&
@@ -3047,13 +3116,13 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
 		selector = regulator_map_voltage(rdev, min_uV, max_uV);
 		if (selector < 0) {
 			ret = selector;
-			goto out2;
+			goto out;
 		}
 
 		best_supply_uV = _regulator_list_voltage(rdev, selector, 0);
 		if (best_supply_uV < 0) {
 			ret = best_supply_uV;
-			goto out2;
+			goto out;
 		}
 
 		best_supply_uV += rdev->desc->min_dropout_uV;
@@ -3061,7 +3130,7 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
 		current_supply_uV = _regulator_get_voltage(rdev->supply->rdev);
 		if (current_supply_uV < 0) {
 			ret = current_supply_uV;
-			goto out2;
+			goto out;
 		}
 
 		supply_change_uV = best_supply_uV - current_supply_uV;
@@ -3073,7 +3142,7 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
 		if (ret) {
 			dev_err(&rdev->dev, "Failed to increase supply voltage: %d\n",
 					ret);
-			goto out2;
+			goto out;
 		}
 	}
 
@@ -3083,7 +3152,7 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
 		ret = _regulator_do_set_suspend_voltage(rdev, min_uV,
 							max_uV, state);
 	if (ret < 0)
-		goto out2;
+		goto out;
 
 	if (supply_change_uV < 0) {
 		ret = regulator_set_voltage_unlocked(rdev->supply,
@@ -3096,11 +3165,6 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
 	}
 
 out:
-	return ret;
-out2:
-	voltage->min_uV = old_min_uV;
-	voltage->max_uV = old_max_uV;
-
 	return ret;
 }
 
@@ -3274,17 +3338,8 @@ static int regulator_balance_voltage(struct regulator_dev *rdev,
 			goto out;
 		}
 
-		/*
-		 * Lock just the supply regulators, as the regulator itself
-		 * is already locked by regulator_lock_coupled().
-		 */
-		if (best_rdev->supply)
-			regulator_lock_supply(best_rdev->supply->rdev);
-
 		ret = regulator_set_voltage_rdev(best_rdev, best_uV,
 						 best_uV, state);
-		if (best_rdev->supply)
-			regulator_unlock_supply(best_rdev->supply->rdev);
 
 		if (ret < 0)
 			goto out;
@@ -3316,12 +3371,12 @@ int regulator_set_voltage(struct regulator *regulator, int min_uV, int max_uV)
 {
 	int ret = 0;
 
-	regulator_lock_supply(regulator->rdev);
+	regulator_lock_dependent(regulator->rdev);
 
 	ret = regulator_set_voltage_unlocked(regulator, min_uV, max_uV,
 					     PM_SUSPEND_ON);
 
-	regulator_unlock_supply(regulator->rdev);
+	regulator_unlock_dependent(regulator->rdev);
 
 	return ret;
 }
@@ -3399,12 +3454,12 @@ int regulator_set_suspend_voltage(struct regulator *regulator, int min_uV,
 	if (regulator_check_states(state) || state == PM_SUSPEND_ON)
 		return -EINVAL;
 
-	regulator_lock_supply(regulator->rdev);
+	regulator_lock_dependent(regulator->rdev);
 
 	ret = _regulator_set_suspend_voltage(regulator, min_uV,
 					     max_uV, state);
 
-	regulator_unlock_supply(regulator->rdev);
+	regulator_unlock_dependent(regulator->rdev);
 
 	return ret;
 }
@@ -3596,11 +3651,11 @@ int regulator_get_voltage(struct regulator *regulator)
 {
 	int ret;
 
-	regulator_lock_supply(regulator->rdev);
+	regulator_lock_dependent(regulator->rdev);
 
 	ret = _regulator_get_voltage(regulator->rdev);
 
-	regulator_unlock_supply(regulator->rdev);
+	regulator_unlock_dependent(regulator->rdev);
 
 	return ret;
 }