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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: Christian Kohlschütter <christian@kohlschutter.com>
Link: https://lore.kernel.org/r/20220818124646.6005-1-christian@kohlschutter.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Christian Kohlschütter 2022-08-18 12:46:47 +00:00 committed by Mark Brown
parent ee94aff262
commit 8a866d527a
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
1 changed files with 33 additions and 19 deletions
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52
drivers/regulator/core.c
View File

@ -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