[PATCH AUTOSEL 6.2 5/9] soundwire: bus: Fix unbalanced pm_runtime_put() causing usage count underflow

Sasha Levin
2023-05-10T20:50:55Z

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