regulator: core: fix deadlock on regulator enable

When updating the operating mode as part of regulator enable, the caller
has already locked the regulator tree and drms_uA_update() must not try
to do the same in order not to trigger a deadlock.

The lock inversion is reported by lockdep as:

  ======================================================
  WARNING: possible circular locking dependency detected
  6.1.0-next-20221215 torvalds#142 Not tainted
  ------------------------------------------------------
  udevd/154 is trying to acquire lock:
  ffffc11f123d7e50 (regulator_list_mutex){+.+.}-{3:3}, at: regulator_lock_dependent+0x54/0x280

  but task is already holding lock:
  ffff80000e4c36e8 (regulator_ww_class_acquire){+.+.}-{0:0}, at: regulator_enable+0x34/0x80

  which lock already depends on the new lock.

  ...

   Possible unsafe locking scenario:

         CPU0                    CPU1
         ----                    ----
    lock(regulator_ww_class_acquire);
                                 lock(regulator_list_mutex);
                                 lock(regulator_ww_class_acquire);
    lock(regulator_list_mutex);

   *** DEADLOCK ***

just before probe of a Qualcomm UFS controller (occasionally) deadlocks
when enabling one of its regulators.

Fixes: 9243a19 ("regulator: core: Change voltage setting path")
Fixes: f8702f9 ("regulator: core: Use ww_mutex for regulators locking")
Cc: [email protected]      # 5.0
Signed-off-by: Johan Hovold <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>

drivers/regulator/core.c

@@ -1002,7 +1002,7 @@ static int drms_uA_update(struct regulator_dev *rdev)
 		/* get input voltage */
 		input_uV = 0;
 		if (rdev->supply)
-			input_uV = regulator_get_voltage(rdev->supply);
+			input_uV = regulator_get_voltage_rdev(rdev->supply->rdev);
 		if (input_uV <= 0)
 			input_uV = rdev->constraints->input_uV;