regulator: core: resolve supply for boot-on/always-on regulators

For the boot-on/always-on regulators the set_machine_constrainst() is
called before resolving rdev->supply. Thus the code would try to enable
rdev before enabling supplying regulator. Enforce resolving supply
regulator before enabling rdev.

Fixes: aea6cb9 ("regulator: resolve supply after creating regulator")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210519221224.2868496-1-dmitry.baryshkov@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -1425,6 +1425,12 @@ static int set_machine_constraints(struct regulator_dev *rdev)
 	 * and we have control then make sure it is enabled.
 	 */
 	if (rdev->constraints->always_on || rdev->constraints->boot_on) {
+		/* If we want to enable this regulator, make sure that we know
+		 * the supplying regulator.
+		 */
+		if (rdev->supply_name && !rdev->supply)
+			return -EPROBE_DEFER;
+
 		if (rdev->supply) {
 			ret = regulator_enable(rdev->supply);
 			if (ret < 0) {