linux-kernel - [PATCH] regulator: core: Resolve supplies before disabling unused regulators

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Message-Id: <20170216170629.19927-1-javier@osg.samsung.com>
Date:   Thu, 16 Feb 2017 14:06:28 -0300
From:   Javier Martinez Canillas <javier@....samsung.com>
To:     linux-kernel@...r.kernel.org
Cc:     Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Andi Shyti <andi.shyti@...sung.com>,
        Mark Brown <broonie@...nel.org>,
        Shuah Khan <shuahkh@....samsung.com>,
        Inki Dae <inki.dae@...sung.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Javier Martinez Canillas <javier@....samsung.com>
Subject: [PATCH] regulator: core: Resolve supplies before disabling unused regulators

After commit 66d228a2bf03 ("regulator: core: Don't use regulators as
supplies until the parent is bound"), input supplies aren't resolved
if the input supplies parent device has not been bound. This prevent
regulators to hold an invalid reference if its supply parent device
driver probe is deferred.

But this causes issues on some boards where a PMIC's regulator use as
input supply a regulator from another PMIC whose driver is registered
after the driver for the former.

In this case the regulators for the first PMIC will fail to resolve
input supplies on regulators registration (since the other PMIC wasn't
probed yet). And when the core attempts to resolve again latter when
the other PMIC registers its own regulators, it will fail again since
the parent device isn't bound yet.

This will cause some parent supplies to never be resolved and wrongly
be disabled on boot due taking them as unused.

To solve this problem don't attempt to resolve the pending regulators
input supplies on regulator registration, but instead do it just once
before disabling the unused regulators.

This also makes the regulator resolve logic more efficient since there
is no need to attempt to resolve the input supplies on each regulator
registration, and doing it once before disabling the unused is enough.

Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>

---

Hello,

I found this issue since after the mentioned commit the Exynos5800 Peach
Pi Chromebook was failing to boot as reported by kernelci:

https://storage.kernelci.org/broonie-regulator/regulator-fix-v4.10-rc6-58-g3761de31e8aa/arm-exynos_defconfig/lab-collabora/boot-exynos5800-peach-pi.html

This patch fixes the issue.

Best regards,
Javier

 drivers/regulator/core.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index cc68604ad97a..193e79a51ce8 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -4108,9 +4108,6 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	dev_set_drvdata(&rdev->dev, rdev);
 	rdev_init_debugfs(rdev);

-	/* try to resolve regulators supply since a new one was registered */
-	class_for_each_device(&regulator_class, NULL, NULL,
-			      regulator_register_resolve_supply);
 	kfree(config);
 	return rdev;

@@ -4556,6 +4553,16 @@ static int __init regulator_init_complete(void)
 	if (of_have_populated_dt())
 		has_full_constraints = true;

+	/*
+	 * Regulators may had failed to resolve their input supplies
+	 * when were registered, either because the input supply was
+	 * not registered yet or because its parent device was not
+	 * bound yet. So attempt to resolve the input supplies for
+	 * pending regulators before trying to disable unused ones.
+	 */
+	class_for_each_device(&regulator_class, NULL, NULL,
+			      regulator_register_resolve_supply);
+
 	/* If we have a full configuration then disable any regulators
 	 * we have permission to change the status for and which are
 	 * not in use or always_on.  This is effectively the default
-- 
2.9.3