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    Subject[PATCH V3] regulator: core: Don't use regulators as supplies until the parent is bound
    Date
    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 and if the parent device for the supply
    and the regulator are different. 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 from another device.

    Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
    ---

    Changes since V2:
    - Fixed comment formatting

    Changes since V1:
    - Updated patch per Mark's input to only prevent resolving the supply
    if the supply's parent is different from the regulator's and the
    supply's parent device is not bound.
    - Added comment.

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

    diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
    index 04baac9a165b..bcf67abd1cd2 100644
    --- a/drivers/regulator/core.c
    +++ b/drivers/regulator/core.c
    @@ -1553,6 +1553,19 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
    }
    }

    + /*
    + * If the supply's parent device is not the same as the
    + * regulator's parent device, then ensure the parent device
    + * is bound before we resolve the supply, in case the parent
    + * device get probe deferred and unregisters the supply.
    + */
    + if (r->dev.parent && r->dev.parent != rdev->dev.parent) {
    + if (!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
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