On Fri, 26 Feb 2016 18:39:57 +0100, ville.syrjala@linux.intel.com wrote:
From: Ville Syrjälä ville.syrjala@linux.intel.com
azx_probe_continue() uses pm_runtime_put_noidle() to drop the rpm usage_count, which means that if it's the last reference the autosuspend of the controller won't actually happen. So if the codecs autosuspend before the azx_probe_continue() drops the last reference we'll fail to autosuspend the controller. This does happen in practice, but not every time. As can be seen in [1] the controller autosuspend attempt fails due to the usage_count when suspending the codecs. A bit later we see the the contoller usage_count dropping to zero without further attempts at autosuspend.
Fix the problem by using pm_runtime_put_autosuspend() instead, which will kick off the autosuspend of the controller even if the codecs are already asleep. As can be seen in [2] the controller autosuspend still fails while suspending the codecs, but later on we see another autosuspend attempt after dropping the usage_count to 0.
I was also a bit worried that there might still be a race between the controller autosuspend and the rest of the code in azx_probe_continue(). So I also tried replacing the the put_noidle() with put_sync_suspend(). No explosions occurred, so I'm somewhat satisfied that there are no serious problems in this area.
A good catch!
The change should be safe, as this is the point where already all initialization has been done.
I queued it to for-next branch, since this is no super-urgent issue to be fixed in 4.5.
thanks,
Takashi