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@xxxxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
> ---
> 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;
> }
>
