From 8a866d527ac0441c0eb14a991fa11358b476b11d Mon Sep 17 00:00:00 2001 From: Christian Kohlschütter Date: Thu, 18 Aug 2022 12:46:47 +0000 Subject: regulator: core: Resolve supply name earlier to prevent double-init MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Link: https://lore.kernel.org/r/20220818124646.6005-1-christian@kohlschutter.com Signed-off-by: Mark Brown --- drivers/regulator/core.c | 52 ++++++++++++++++++++++++++++++------------------ 1 file changed, 33 insertions(+), 19 deletions(-) (limited to 'drivers/regulator') diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c index d8373cb04f90..a5033c6ba01e 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -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(®ulator_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 -- cgit v1.2.3