regulator: Flag uncontrollable regulators as always_on

While we currently assume that regulators with no control available are
just uncontionally enabled this isn't always as clearly displayed to
users as is desirable, for example the code for disabling unused
regulators will log that it is about to disable them. Clean this up a
bit by setting always_on during constraint evaluation if we have no
available mechanism for controlling the regualtor so things that check
the constraint will do the right thing.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220325144637.1543496-1-broonie@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: broonie

drivers/regulator/core.c

@@ -1522,6 +1522,24 @@ static int set_machine_constraints(struct regulator_dev *rdev)
 		}
 	}
 
+	/*
+	 * If there is no mechanism for controlling the regulator then
+	 * flag it as always_on so we don't end up duplicating checks
+	 * for this so much.  Note that we could control the state of
+	 * a supply to control the output on a regulator that has no
+	 * direct control.
+	 */
+	if (!rdev->ena_pin && !ops->enable) {
+		if (rdev->supply_name && !rdev->supply)
+			return -EPROBE_DEFER;
+
+		if (rdev->supply)
+			rdev->constraints->always_on =
+				rdev->supply->rdev->constraints->always_on;
+		else
+			rdev->constraints->always_on = true;
+	}
+
 	/* If the constraints say the regulator should be on at this point
 	 * and we have control then make sure it is enabled.
 	 */