regulator: core: Avoid debugfs: Directory ... already present! error

Sometimes regulator_get() gets called twice for the same supply on the
same device. This may happen e.g. when a framework / library is used
which uses the regulator; and the driver itself also needs to enable
the regulator in some cases where the framework will not enable it.

Commit ff268b56 ("regulator: core: Don't spew backtraces on
duplicate sysfs") already takes care of the backtrace which would
trigger when creating a duplicate consumer symlink under
/sys/class/regulator/regulator.%d in this scenario.

Commit c33d4423 ("debugfs: make error message a bit more verbose")
causes a new error to get logged in this scenario:

[   26.938425] debugfs: Directory 'wm5102-codec-MICVDD' with parent 'spi-WM510204:00-MICVDD' already present!

There is no _nowarn variant of debugfs_create_dir(), but we can detect
and avoid this problem by checking the return value of the earlier
sysfs_create_link_nowarn() call.

Add a check for the earlier sysfs_create_link_nowarn() failing with
-EEXIST and skip the debugfs_create_dir() call in that case, avoiding
this error getting logged.

Fixes: c33d4423 ("debugfs: make error message a bit more verbose")
Cc: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20210122183250.370571-1-hdegoede@redhat.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -1617,7 +1617,7 @@ static struct regulator *create_regulator(struct regulator_dev *rdev,
 					  const char *supply_name)
 {
 	struct regulator *regulator;
-	int err;
+	int err = 0;
 
 	if (dev) {
 		char buf[REG_STR_SIZE];
@@ -1663,8 +1663,8 @@ static struct regulator *create_regulator(struct regulator_dev *rdev,
 		}
 	}
 
-	regulator->debugfs = debugfs_create_dir(supply_name,
-						rdev->debugfs);
+	if (err != -EEXIST)
+		regulator->debugfs = debugfs_create_dir(supply_name, rdev->debugfs);
 	if (!regulator->debugfs) {
 		rdev_dbg(rdev, "Failed to create debugfs directory\n");
 	} else {