Re: [PATCH 3/3] soundwire: qcom: add wake up interrupt support

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

>> Not following, sorry. if you use pm_runtime functions and it so happens
>> that the resume already started, then those routines would wait for the
>> resume to complete.
> yes that is true,
> 
> TBH, I was trying to reproduce the issue since morning to collect some
> traces but no luck so far, I hit these issues pretty much rarely. Now
> code has changed since few months back am unable to reproduce this
> anymore. Or it might be just the state of code I had while writing this up.
> 
> But when I hit the issue, this is how it looks like:
> 
> 1. IRQ Wake interrupt resume parent.
> 
> 2. parent is in middle of resuming
> 
> 3. Slave Pend interrupt in controller fired up
> 
> 4. because of (3) child resume is requested and then the parent resume
> blocked on (2) to finish.
> 
> 5. from (2) we also trying to resume child.
> 
> 6. (5) is blocked on (4) to finish which is blocked on (2) to finish
> 
> we are dead locked. Only way for me to avoid dead lock was to wake the
> child up after IRQ wake interrupts.

Maybe a red-herring, but we're seen cases like this where we called
pm_runtime_get_sync() while resuming, that didn't go so well. I would
look into the use of _no_pm routines if you are already trying to resume.