regulator: core: Support bypass mode

Many regulators support a bypass mode where they simply switch their
input supply to the output. This is mainly used in low power retention
states where power consumption is extremely low so higher voltage or
less clean supplies can be used.

Support this by providing ops for the drivers and a consumer API which
allows the device to be put into bypass mode if all consumers enable it
and the machine enables permission for this.

This is not supported as a mode since the existing modes are rarely used
due to fuzzy definition and mostly redundant with modern hardware which is
able to respond promptly to load changes.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Graeme Gregory <gg@slimlogic.co.uk>

1 files changed, 85 insertions, 0 deletions

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 48385318175..64e16053975 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -77,6 +77,7 @@ struct regulator {
 	struct device *dev;
 	struct list_head list;
 	unsigned int always_on:1;
+	unsigned int bypass:1;
 	int uA_load;
 	int min_uV;
 	int max_uV;
@@ -394,6 +395,9 @@ static ssize_t regulator_status_show(struct device *dev,
 	case REGULATOR_STATUS_STANDBY:
 		label = "standby";
 		break;
+	case REGULATOR_STATUS_BYPASS:
+		label = "bypass";
+		break;
 	case REGULATOR_STATUS_UNDEFINED:
 		label = "undefined";
 		break;
@@ -585,6 +589,27 @@ static ssize_t regulator_suspend_standby_state_show(struct device *dev,
 static DEVICE_ATTR(suspend_standby_state, 0444,
 		regulator_suspend_standby_state_show, NULL);
 
+static ssize_t regulator_bypass_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct regulator_dev *rdev = dev_get_drvdata(dev);
+	const char *report;
+	bool bypass;
+	int ret;
+
+	ret = rdev->desc->ops->get_bypass(rdev, &bypass);
+
+	if (ret != 0)
+		report = "unknown";
+	else if (bypass)
+		report = "enabled";
+	else
+		report = "disabled";
+
+	return sprintf(buf, "%s\n", report);
+}
+static DEVICE_ATTR(bypass, 0444,
+		   regulator_bypass_show, NULL);
 
 /*
  * These are the only attributes are present for all regulators.
@@ -2674,6 +2699,59 @@ out:
 EXPORT_SYMBOL_GPL(regulator_set_optimum_mode);
 
 /**
+ * regulator_allow_bypass - allow the regulator to go into bypass mode
+ *
+ * @regulator: Regulator to configure
+ * @allow: enable or disable bypass mode
+ *
+ * Allow the regulator to go into bypass mode if all other consumers
+ * for the regulator also enable bypass mode and the machine
+ * constraints allow this.  Bypass mode means that the regulator is
+ * simply passing the input directly to the output with no regulation.
+ */
+int regulator_allow_bypass(struct regulator *regulator, bool enable)
+{
+	struct regulator_dev *rdev = regulator->rdev;
+	int ret = 0;
+
+	if (!rdev->desc->ops->set_bypass)
+		return 0;
+
+	if (rdev->constraints &&
+	    !(rdev->constraints->valid_ops_mask & REGULATOR_CHANGE_BYPASS))
+		return 0;
+
+	mutex_lock(&rdev->mutex);
+
+	if (enable && !regulator->bypass) {
+		rdev->bypass_count++;
+
+		if (rdev->bypass_count == rdev->open_count) {
+			ret = rdev->desc->ops->set_bypass(rdev, enable);
+			if (ret != 0)
+				rdev->bypass_count--;
+		}
+
+	} else if (!enable && regulator->bypass) {
+		rdev->bypass_count--;
+
+		if (rdev->bypass_count != rdev->open_count) {
+			ret = rdev->desc->ops->set_bypass(rdev, enable);
+			if (ret != 0)
+				rdev->bypass_count++;
+		}
+	}
+
+	if (ret == 0)
+		regulator->bypass = enable;
+
+	mutex_unlock(&rdev->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(regulator_allow_bypass);
+
+/**
  * regulator_register_notifier - register regulator event notifier
  * @regulator: regulator source
  * @nb: notifier block
@@ -3036,6 +3114,11 @@ static int add_regulator_attributes(struct regulator_dev *rdev)
 		if (status < 0)
 			return status;
 	}
+	if (ops->get_bypass) {
+		status = device_create_file(dev, &dev_attr_bypass);
+		if (status < 0)
+			return status;
+	}
 
 	/* some attributes are type-specific */
 	if (rdev->desc->type == REGULATOR_CURRENT) {
@@ -3124,6 +3207,8 @@ static void rdev_init_debugfs(struct regulator_dev *rdev)
 			   &rdev->use_count);
 	debugfs_create_u32("open_count", 0444, rdev->debugfs,
 			   &rdev->open_count);
+	debugfs_create_u32("bypass_count", 0444, rdev->debugfs,
+			   &rdev->bypass_count);
 }
 
 /**