[RFC v1 4/4] regulator: core: Move regulator supply resolving to the probe function

[Saravana Kannan <saravanak@google.com>]

We can simplify the regulator's supply resolving code if we resolve the
supply in the regulator's probe function. This allows us to:

- Consolidate the supply resolution code to one place.
- Avoid the need for recursion by allow driver core to take care of
  handling dependencies.
- Avoid races and simplify locking by reusing the guarantees provided by
  driver core.
- Avoid last minute/lazy resolving during regulator_get().
- Simplify error handling because we can assume the supply has been
  resolved once a regulator is probed.
- Allow driver core to use device links/fw_devlink, where available, to
  resolve the regulator supplies in the optimal order.

Signed-off-by: Saravana Kannan <saravanak@google.com>
---
 drivers/regulator/core.c | 27 ++++++---------------------
 1 file changed, 6 insertions(+), 21 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index d5f9fdd79c14..f3bf74d1a81d 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1952,7 +1952,7 @@ static struct regulator_dev *regulator_dev_lookup(struct device *dev,
 		if (node) {
 			r = of_find_regulator_by_node(node);
 			of_node_put(node);
-			if (r)
+			if (r && r->dev.links.status == DL_DEV_DRIVER_BOUND)
 				return r;
 
 			/*
@@ -1982,11 +1982,11 @@ static struct regulator_dev *regulator_dev_lookup(struct device *dev,
 	}
 	mutex_unlock(&regulator_list_mutex);
 
-	if (r)
+	if (r && r->dev.links.status == DL_DEV_DRIVER_BOUND)
 		return r;
 
 	r = regulator_lookup_by_name(supply);
-	if (r)
+	if (r && r->dev.links.status == DL_DEV_DRIVER_BOUND)
 		return r;
 
 	return ERR_PTR(-ENODEV);
@@ -2050,13 +2050,6 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 		}
 	}
 
-	/* Recursively resolve the supply of the supply */
-	ret = regulator_resolve_supply(r);
-	if (ret < 0) {
-		put_device(&r->dev);
-		goto out;
-	}
-
 	/*
 	 * Recheck rdev->supply with rdev->mutex lock held to avoid a race
 	 * between rdev->supply null check and setting rdev->supply in
@@ -2178,13 +2171,6 @@ struct regulator *_regulator_get(struct device *dev, const char *id,
 		return regulator;
 	}
 
-	ret = regulator_resolve_supply(rdev);
-	if (ret < 0) {
-		regulator = ERR_PTR(ret);
-		put_device(&rdev->dev);
-		return regulator;
-	}
-
 	if (!try_module_get(rdev->owner)) {
 		regulator = ERR_PTR(-EPROBE_DEFER);
 		put_device(&rdev->dev);
@@ -5649,9 +5635,6 @@ regulator_register(struct device *dev,
 	regulator_resolve_coupling(rdev);
 	mutex_unlock(&regulator_list_mutex);
 
-	/* try to resolve regulators supply since a new one was registered */
-	bus_for_each_dev(&regulator_bus, NULL, NULL,
-			 regulator_register_resolve_supply);
 	kfree(config);
 	return rdev;
 
@@ -5782,7 +5765,9 @@ static const struct dev_pm_ops __maybe_unused regulator_pm_ops = {
 
 static int regulator_drv_probe(struct device *dev)
 {
-	return 0;
+	struct regulator_dev *rdev = dev_to_rdev(dev);
+
+	return regulator_resolve_supply(rdev);
 }
 
 static struct device_driver regulator_drv = {
-- 
2.39.2.637.g21b0678d19-goog