Unverified Commit 8a866d52 authored by Christian Kohlschütter's avatar Christian Kohlschütter Committed by Mark Brown
Browse files

regulator: core: Resolve supply name earlier to prevent double-init 



Previously, an unresolved regulator supply reference upon calling
regulator_register on an always-on or boot-on regulator caused
set_machine_constraints to be called twice.

This in turn may initialize the regulator twice, leading to voltage
glitches that are timing-dependent. A simple, unrelated configuration
change may be enough to hide this problem, only to be surfaced by
chance.

One such example is the SD-Card voltage regulator in a NanoPI R4S that
would not initialize reliably unless the registration flow was just
complex enough to allow the regulator to properly reset between calls.

Fix this by re-arranging regulator_register, trying resolve the
regulator's supply early enough that set_machine_constraints does not
need to be called twice.

Signed-off-by: default avatarChristian Kohlschütter <christian@kohlschutter.com>
Link: https://lore.kernel.org/r/20220818124646.6005-1-christian@kohlschutter.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent ee94aff2

drivers/regulator/core.c

+33 −19
Original line number Diff line number Diff line
@@ -5496,7 +5496,39 @@ regulator_register(const struct regulator_desc *regulator_desc, 
	BLOCKING_INIT_NOTIFIER_HEAD(&rdev->notifier);

	INIT_DELAYED_WORK(&rdev->disable_work, regulator_disable_work);



	/* preform any regulator specific init */

	/* set regulator constraints */

	if (init_data)

		rdev->constraints = kmemdup(&init_data->constraints,

					    sizeof(*rdev->constraints),

					    GFP_KERNEL);

	else

		rdev->constraints = kzalloc(sizeof(*rdev->constraints),

					    GFP_KERNEL);

	if (!rdev->constraints) {

		ret = -ENOMEM;

		goto clean;

	}



	if (init_data && init_data->supply_regulator)

		rdev->supply_name = init_data->supply_regulator;

	else if (regulator_desc->supply_name)

		rdev->supply_name = regulator_desc->supply_name;



	if ((rdev->supply_name && !rdev->supply) &&

			(rdev->constraints->always_on ||

			 rdev->constraints->boot_on)) {

		/* Try to resolve the name of the supplying regulator here first

		 * so we prevent double-initializing the regulator, which may

		 * cause timing-specific voltage brownouts/glitches that are

		 * hard to debug.

		 */

		ret = regulator_resolve_supply(rdev);

		if (ret)

			rdev_dbg(rdev, "unable to resolve supply early: %pe\n",

					 ERR_PTR(ret));

	}



	/* perform any regulator specific init */

	if (init_data && init_data->regulator_init) {

		ret = init_data->regulator_init(rdev->reg_data);

		if (ret < 0)
@@ -5522,24 +5554,6 @@ regulator_register(const struct regulator_desc *regulator_desc, 
		    (unsigned long) atomic_inc_return(&regulator_no));

	dev_set_drvdata(&rdev->dev, rdev);



	/* set regulator constraints */

	if (init_data)

		rdev->constraints = kmemdup(&init_data->constraints,

					    sizeof(*rdev->constraints),

					    GFP_KERNEL);

	else

		rdev->constraints = kzalloc(sizeof(*rdev->constraints),

					    GFP_KERNEL);

	if (!rdev->constraints) {

		ret = -ENOMEM;

		goto wash;

	}



	if (init_data && init_data->supply_regulator)

		rdev->supply_name = init_data->supply_regulator;

	else if (regulator_desc->supply_name)

		rdev->supply_name = regulator_desc->supply_name;



	ret = set_machine_constraints(rdev);

	if (ret == -EPROBE_DEFER) {

		/* Regulator might be in bypass mode and so needs its supply