regulator: core: Resolve supplies before disabling unused regulators

After commit 66d228a2bf03 ("regulator: core: Don't use regulators as
supplies until the parent is bound"), input supplies aren't resolved
if the input supplies parent device has not been bound. This prevent
regulators to hold an invalid reference if its supply parent device
driver probe is deferred.

But this causes issues on some boards where a PMIC's regulator use as
input supply a regulator from another PMIC whose driver is registered
after the driver for the former.

In this case the regulators for the first PMIC will fail to resolve
input supplies on regulators registration (since the other PMIC wasn't
probed yet). And when the core attempts to resolve again latter when
the other PMIC registers its own regulators, it will fail again since
the parent device isn't bound yet.

This will cause some parent supplies to never be resolved and wrongly
be disabled on boot due taking them as unused.

To solve this problem, also attempt to resolve the pending regulators
input supplies before disabling the unused regulators.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -4540,6 +4540,16 @@ static int __init regulator_init_complete(void)
 	if (of_have_populated_dt())
 		has_full_constraints = true;
 
+	/*
+	 * Regulators may had failed to resolve their input supplies
+	 * when were registered, either because the input supply was
+	 * not registered yet or because its parent device was not
+	 * bound yet. So attempt to resolve the input supplies for
+	 * pending regulators before trying to disable unused ones.
+	 */
+	class_for_each_device(&regulator_class, NULL, NULL,
+			      regulator_register_resolve_supply);
+
 	/* If we have a full configuration then disable any regulators
 	 * we have permission to change the status for and which are
 	 * not in use or always_on.  This is effectively the default