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Message-Id: <EC5FFA28-21D3-4FBB-B188-7DB1C9E1AA9E@kohlschutter.com>
Date: Thu, 4 Aug 2022 12:44:29 +0200
From: Christian Kohlschütter
<christian@...lschutter.com>
To: Vincent Legoll <vincent.legoll@...il.com>,
Mark Brown <broonie@...nel.org>
Cc: Heiko Stübner <heiko@...ech.de>,
Liam Girdwood <lgirdwood@...il.com>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Linux MMC List <linux-mmc@...r.kernel.org>,
"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
Markus Reichl <m.reichl@...etechno.de>,
Robin Murphy <robin.murphy@....com>, wens@...nel.org
Subject: [PATCH v3] 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 Kohlsch=C3=BCtter <christian@...lschutter.com>
---
drivers/regulator/core.c | 51 +++++++++++++++++++++++++---------------
1 file changed, 32 insertions(+), 19 deletions(-)
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 398c8d6afd4..5c2b97ea633 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -5492,7 +5492,38 @@ regulator_register(const struct regulator_desc =
*regulator_desc,
BLOCKING_INIT_NOTIFIER_HEAD(&rdev->notifier);
INIT_DELAYED_WORK(&rdev->disable_work, regulator_disable_work);
=20
- /* preform any regulator specific init */
+ /* set regulator constraints */
+ if (init_data)
+ rdev->constraints =3D kmemdup(&init_data->constraints,
+ sizeof(*rdev->constraints),
+ GFP_KERNEL);
+ else
+ rdev->constraints =3D =
kzalloc(sizeof(*rdev->constraints),
+ GFP_KERNEL);
+ if (!rdev->constraints) {
+ ret =3D -ENOMEM;
+ goto clean;
+ }
+
+ if (init_data && init_data->supply_regulator)
+ rdev->supply_name =3D init_data->supply_regulator;
+ else if (regulator_desc->supply_name)
+ rdev->supply_name =3D regulator_desc->supply_name;
+
+ if ((rdev->supply_name && !rdev->supply) && rdev->constraints
+ && (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 =3D 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 =3D init_data->regulator_init(rdev->reg_data);
if (ret < 0)
@@ -5518,24 +5549,6 @@ regulator_register(const struct regulator_desc =
*regulator_desc,
(unsigned long) atomic_inc_return(®ulator_no));
dev_set_drvdata(&rdev->dev, rdev);
=20
- /* set regulator constraints */
- if (init_data)
- rdev->constraints =3D kmemdup(&init_data->constraints,
- sizeof(*rdev->constraints),
- GFP_KERNEL);
- else
- rdev->constraints =3D =
kzalloc(sizeof(*rdev->constraints),
- GFP_KERNEL);
- if (!rdev->constraints) {
- ret =3D -ENOMEM;
- goto wash;
- }
-
- if (init_data && init_data->supply_regulator)
- rdev->supply_name =3D init_data->supply_regulator;
- else if (regulator_desc->supply_name)
- rdev->supply_name =3D regulator_desc->supply_name;
-
ret =3D set_machine_constraints(rdev);
if (ret =3D=3D -EPROBE_DEFER) {
/* Regulator might be in bypass mode and so needs its =
supply
--=20
2.36.2
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