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    Subject[PATCH AUTOSEL 6.2 5/9] soundwire: bus: Fix unbalanced pm_runtime_put() causing usage count underflow
    Date
    From: Richard Fitzgerald <rf@opensource.cirrus.com>

    [ Upstream commit e9537962519e88969f5f69cd0571eb4f6984403c ]

    This reverts commit
    443a98e649b4 ("soundwire: bus: use pm_runtime_resume_and_get()")

    Change calls to pm_runtime_resume_and_get() back to pm_runtime_get_sync().
    This fixes a usage count underrun caused by doing a pm_runtime_put() even
    though pm_runtime_resume_and_get() returned an error.

    The three affected functions ignore -EACCES error from trying to get
    pm_runtime, and carry on, including a put at the end of the function.
    But pm_runtime_resume_and_get() does not increment the usage count if it
    returns an error. So in the -EACCES case you must not call
    pm_runtime_put().

    The documentation for pm_runtime_get_sync() says:
    "Consider using pm_runtime_resume_and_get() ... as this is likely to
    result in cleaner code."

    In this case I don't think it results in cleaner code because the
    pm_runtime_put() at the end of the function would have to be conditional on
    the return value from pm_runtime_resume_and_get() at the top of the
    function.

    pm_runtime_get_sync() doesn't have this problem because it always
    increments the count, so always needs a put. The code can just flow through
    and do the pm_runtime_put() unconditionally.

    Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
    Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
    Link: https://lore.kernel.org/r/20230406134640.8582-1-rf@opensource.cirrus.com
    Signed-off-by: Vinod Koul <vkoul@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/soundwire/bus.c | 15 ++++++++++-----
    1 file changed, 10 insertions(+), 5 deletions(-)

    diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
    index 76515c33e639e..4fd221d0cc818 100644
    --- a/drivers/soundwire/bus.c
    +++ b/drivers/soundwire/bus.c
    @@ -571,9 +571,11 @@ int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
    {
    int ret;

    - ret = pm_runtime_resume_and_get(&slave->dev);
    - if (ret < 0 && ret != -EACCES)
    + ret = pm_runtime_get_sync(&slave->dev);
    + if (ret < 0 && ret != -EACCES) {
    + pm_runtime_put_noidle(&slave->dev);
    return ret;
    + }

    ret = sdw_nread_no_pm(slave, addr, count, val);

    @@ -595,9 +597,11 @@ int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, const u8 *val)
    {
    int ret;

    - ret = pm_runtime_resume_and_get(&slave->dev);
    - if (ret < 0 && ret != -EACCES)
    + ret = pm_runtime_get_sync(&slave->dev);
    + if (ret < 0 && ret != -EACCES) {
    + pm_runtime_put_noidle(&slave->dev);
    return ret;
    + }

    ret = sdw_nwrite_no_pm(slave, addr, count, val);

    @@ -1565,9 +1569,10 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)

    sdw_modify_slave_status(slave, SDW_SLAVE_ALERT);

    - ret = pm_runtime_resume_and_get(&slave->dev);
    + ret = pm_runtime_get_sync(&slave->dev);
    if (ret < 0 && ret != -EACCES) {
    dev_err(&slave->dev, "Failed to resume device: %d\n", ret);
    + pm_runtime_put_noidle(&slave->dev);
    return ret;
    }

    --
    2.39.2
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