regulator: core: disable supply if enabling main regulator fails

For 'always-on' and 'boot-on' regulators, the set_machine_constraints()
may enable supply before enabling the main regulator, however if the
latter fails, the function returns with an error but the supply remains
enabled.

When this happens, the regulator_register() function continues on the
error path where it puts the supply regulator. Since enabling the supply
is not balanced with a disable call, a warning similar to the following
gets issued from _regulator_put():

[ 1.603889] WARNING: CPU: 2 PID: 44 at _regulator_put+0x8c/0xa0
[ 1.603908] Modules linked in:
[ 1.603926] CPU: 2 UID: 0 PID: 44 Comm: kworker/u16:3 Not tainted 6.18.0-rc4 #0 NONE
[ 1.603938] Hardware name: Qualcomm Technologies, Inc. IPQ9574/AP-AL02-C7 (DT)
[ 1.603945] Workqueue: async async_run_entry_fn
[ 1.603958] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 1.603967] pc : _regulator_put+0x8c/0xa0
[ 1.603976] lr : _regulator_put+0x7c/0xa0
...
[ 1.604140] Call trace:
[ 1.604145] _regulator_put+0x8c/0xa0 (P)
[ 1.604156] regulator_register+0x2ec/0xbf0
[ 1.604166] devm_regulator_register+0x60/0xb0
[ 1.604178] rpm_reg_probe+0x120/0x208
[ 1.604187] platform_probe+0x64/0xa8
...

In order to avoid this, change the set_machine_constraints() function to
disable the supply if enabling the main regulator fails.

Fixes: 05f224ca6693 ("regulator: core: Clean enabling always-on regulators + their supplies")
Signed-off-by: Gabor Juhos <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/core.c

···
 	 * and we have control then make sure it is enabled.
 	 */
 	if (rdev->constraints->always_on || rdev->constraints->boot_on) {
+		bool supply_enabled = false;
+
 		/* If we want to enable this regulator, make sure that we know
 		 * the supplying regulator.
 		 */
···
 				rdev->supply = NULL;
 				return ret;
 			}
+			supply_enabled = true;
 		}
 
 		ret = _regulator_do_enable(rdev);
 		if (ret < 0 && ret != -EINVAL) {
 			rdev_err(rdev, "failed to enable: %pe\n", ERR_PTR(ret));
+			if (supply_enabled)
+				regulator_disable(rdev->supply);
 			return ret;
 		}