On 2/27/23 06:29, Richard Fitzgerald wrote:

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

Agreed, in hindsight the move to use pm_runtime_resume_and_get() mostly added issues left and right with limited benefits - just too hard to review and figure out what cases work and which ones don't.

Reviewed-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com

---

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 76515c33e639..4fd221d0cc81 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; }