[PATCH 3/5] regulator: core: Add mechanism to force disable a regulator at boot

[Paul Louvel]

Regulation activity may be enabled by default when the device powers up.
A consumer may query the regulator's state during probe and may disable
it if it is already enabled, potentially resulting in an unbalanced
disable operation:

ret = regulator_is_enabled();
if (ret < 0)
  return ret;

if (ret)
  ret = regulator_disable();
        ^^^^^^^^^^^^^^^^^^^^

Add the 'regulator-boot-force-off' property, which disable the regulator
when setting machine constraints.

Signed-off-by: Paul Louvel <paul.louvel@xxxxxxxxxxx>
---
 drivers/regulator/core.c          | 154 ++++++++++++++++++++------------------
 drivers/regulator/of_regulator.c  |   1 +
 include/linux/regulator/machine.h |   3 +-
 3 files changed, 84 insertions(+), 74 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 14422cfe80e2..b45048ec084a 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1450,6 +1450,81 @@ static int handle_notify_limits(struct regulator_dev *rdev,
 
 	return ret;
 }
+
+/**
+ * regulator_ena_gpio_ctrl - balance enable_count of each GPIO and actual GPIO pin control
+ * @rdev: regulator_dev structure
+ * @enable: enable GPIO at initial use?
+ *
+ * GPIO is enabled in case of initial use. (enable_count is 0)
+ * GPIO is disabled when it is not shared any more. (enable_count <= 1)
+ *
+ * Return: 0 on success or a negative error number on failure.
+ */
+static int regulator_ena_gpio_ctrl(struct regulator_dev *rdev, bool enable)
+{
+	struct regulator_enable_gpio *pin = rdev->ena_pin;
+	int ret;
+
+	if (!pin)
+		return -EINVAL;
+
+	if (enable) {
+		/* Enable GPIO at initial use */
+		if (pin->enable_count == 0) {
+			ret = gpiod_set_value_cansleep(pin->gpiod, 1);
+			if (ret)
+				return ret;
+		}
+
+		pin->enable_count++;
+	} else {
+		if (pin->enable_count > 1) {
+			pin->enable_count--;
+			return 0;
+		}
+
+		/* Disable GPIO if not used */
+		if (pin->enable_count <= 1) {
+			ret = gpiod_set_value_cansleep(pin->gpiod, 0);
+			if (ret)
+				return ret;
+
+			pin->enable_count = 0;
+		}
+	}
+
+	return 0;
+}
+
+static int _regulator_do_disable(struct regulator_dev *rdev)
+{
+	int ret;
+
+	trace_regulator_disable(rdev_get_name(rdev));
+
+	if (rdev->ena_pin) {
+		if (rdev->ena_gpio_state) {
+			ret = regulator_ena_gpio_ctrl(rdev, false);
+			if (ret < 0)
+				return ret;
+			rdev->ena_gpio_state = 0;
+		}
+
+	} else if (rdev->desc->ops->disable) {
+		ret = rdev->desc->ops->disable(rdev);
+		if (ret != 0)
+			return ret;
+	}
+
+	if (rdev->desc->off_on_delay)
+		rdev->last_off = ktime_get_boottime();
+
+	trace_regulator_disable_complete(rdev_get_name(rdev));
+
+	return 0;
+}
+
 /**
  * set_machine_constraints - sets regulator constraints
  * @rdev: regulator source
@@ -1701,6 +1776,12 @@ static int set_machine_constraints(struct regulator_dev *rdev,
 		rdev->last_off = ktime_get();
 	}
 
+	if (rdev->constraints->boot_force_off) {
+		ret = _regulator_do_disable(rdev);
+		if (ret < 0)
+			return ret;
+	}
+
 	if (!rdev->constraints->pw_budget_mW)
 		rdev->constraints->pw_budget_mW = INT_MAX;
 
@@ -2910,51 +2991,6 @@ static void regulator_ena_gpio_free(struct regulator_dev *rdev)
 	rdev->ena_pin = NULL;
 }
 
-/**
- * regulator_ena_gpio_ctrl - balance enable_count of each GPIO and actual GPIO pin control
- * @rdev: regulator_dev structure
- * @enable: enable GPIO at initial use?
- *
- * GPIO is enabled in case of initial use. (enable_count is 0)
- * GPIO is disabled when it is not shared any more. (enable_count <= 1)
- *
- * Return: 0 on success or a negative error number on failure.
- */
-static int regulator_ena_gpio_ctrl(struct regulator_dev *rdev, bool enable)
-{
-	struct regulator_enable_gpio *pin = rdev->ena_pin;
-	int ret;
-
-	if (!pin)
-		return -EINVAL;
-
-	if (enable) {
-		/* Enable GPIO at initial use */
-		if (pin->enable_count == 0) {
-			ret = gpiod_set_value_cansleep(pin->gpiod, 1);
-			if (ret)
-				return ret;
-		}
-
-		pin->enable_count++;
-	} else {
-		if (pin->enable_count > 1) {
-			pin->enable_count--;
-			return 0;
-		}
-
-		/* Disable GPIO if not used */
-		if (pin->enable_count <= 1) {
-			ret = gpiod_set_value_cansleep(pin->gpiod, 0);
-			if (ret)
-				return ret;
-
-			pin->enable_count = 0;
-		}
-	}
-
-	return 0;
-}
 
 /**
  * _regulator_check_status_enabled - check if regulator status can be
@@ -3226,34 +3262,6 @@ int regulator_enable(struct regulator *regulator)
 }
 EXPORT_SYMBOL_GPL(regulator_enable);
 
-static int _regulator_do_disable(struct regulator_dev *rdev)
-{
-	int ret;
-
-	trace_regulator_disable(rdev_get_name(rdev));
-
-	if (rdev->ena_pin) {
-		if (rdev->ena_gpio_state) {
-			ret = regulator_ena_gpio_ctrl(rdev, false);
-			if (ret < 0)
-				return ret;
-			rdev->ena_gpio_state = 0;
-		}
-
-	} else if (rdev->desc->ops->disable) {
-		ret = rdev->desc->ops->disable(rdev);
-		if (ret != 0)
-			return ret;
-	}
-
-	if (rdev->desc->off_on_delay)
-		rdev->last_off = ktime_get_boottime();
-
-	trace_regulator_disable_complete(rdev_get_name(rdev));
-
-	return 0;
-}
-
 /* locks held by regulator_disable() */
 static int _regulator_disable(struct regulator *regulator)
 {
diff --git a/drivers/regulator/of_regulator.c b/drivers/regulator/of_regulator.c
index 09e26febfc83..337629be58ca 100644
--- a/drivers/regulator/of_regulator.c
+++ b/drivers/regulator/of_regulator.c
@@ -132,6 +132,7 @@ static int of_get_regulation_constraints(struct device *dev,
 	constraints->always_on = of_property_read_bool(np, "regulator-always-on");
 	if (!constraints->always_on) /* status change should be possible. */
 		constraints->valid_ops_mask |= REGULATOR_CHANGE_STATUS;
+	constraints->boot_force_off = of_property_read_bool(np, "regulator-boot-force-off");
 
 	constraints->pull_down = of_property_read_bool(np, "regulator-pull-down");
 	constraints->system_critical = of_property_read_bool(np,
diff --git a/include/linux/regulator/machine.h b/include/linux/regulator/machine.h
index 1fc440c5c4c7..35ab9de96e5c 100644
--- a/include/linux/regulator/machine.h
+++ b/include/linux/regulator/machine.h
@@ -227,7 +227,8 @@ struct regulation_constraints {
 	unsigned int active_discharge;
 
 	/* constraint flags */
-	unsigned always_on:1;	/* regulator never off when system is on */
+	unsigned always_on:1;		/* regulator never off when system is on */
+	unsigned boot_force_off:1;	/* force regulator off at boot */
 	unsigned boot_on:1;	/* bootloader/firmware enabled regulator */
 	unsigned apply_uV:1;	/* apply uV constraint if min == max */
 	unsigned ramp_disable:1; /* disable ramp delay */

-- 
2.56.0