linux-kernel - [PATCH] regulator: core: Don't use regulators as supplies until the parent is bound

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Date:   Tue, 10 Jan 2017 11:01:09 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        Jon Hunter <jonathanh@...dia.com>
Subject: [PATCH] regulator: core: Don't use regulators as supplies until the parent is bound

When regulators are successfully registered, we check to see if the
regulator is a supply for any other registered regulator and if so
add the new regulator as the supply for the existing regulator(s).

Some devices, such as Power Management ICs, may register a series of
regulators when probed and there are cases where one of the regulators
may fail to register and defer the probing of the parent device. In this
case any successfully registered regulators would be unregistered so
that they can be re-registered at some time later when the probe is
attempted again. However, if one of the regulators that was registered
was added as a supply to another registered regulator (that did not
belong to the same parent device), then this supply regulator was
unregister again because the parent device is probe deferred, then a
regulator could be holding an invalid reference to a supply regulator
that has been unregistered. This will lead to a system crash if that
regulator is then used.

Although it would be possible to check when unregistering a regulator
if any other regulator in the system is using it as a supply, it still
may not be possible to remove it as a supply if this other regulator is
in use. Therefore, fix this by preventing any regulator from adding
another regulator as a supply if the parent device for the supply
regulator has not been bound. This will allow a parent device that is
registering regulators to be probe deferred and ensure that none of the
regulators it has registered are used as supplies for any other
regulator.

Signed-off-by: Jon Hunter <jonathanh@...dia.com>
---
 drivers/regulator/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 04baac9a165b..8adadcdfed1c 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1553,6 +1553,11 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 		}
 	}

+	if (r->dev.parent && !device_is_bound(r->dev.parent)) {
+		put_device(&r->dev);
+		return -EPROBE_DEFER;
+	}
+
 	/* Recursively resolve the supply of the supply */
 	ret = regulator_resolve_supply(r);
 	if (ret < 0) {
-- 
2.7.4