[PATCH] soundwire: cadence: fix race condition between suspend and Slave device alerts

[Pierre-Louis Bossart]

> Is this timeout for suspend or resume? Somehow I was under the
> assumption that it is former? Or is the result seen on resume?
> 
> Rereading the race describe above in steps, I think this should be
> handled in step c above. Btw is that suspend or runtime suspend which
> causes this? Former would be bigger issue as we should not have work
> running when we return from suspend call. Latter should be dealt with
> anyway as device might be off after suspend.

This happens with a system suspend. Because we disable the interrupts, 
the workqueue never completes, and we have a timeout on system resume.

That's why we want to prevent the workqueue from starting, or let it 
complete, but not have this zombie state where we suspend but there's 
still a wait for completion that times out later. The point here is 
really  making sure the workqueue is not used before suspend.