[Sound-open-firmware] the SOF state machine issue

[Liam Girdwood]

On Wed, 2018-07-18 at 09:59 +0800, zhigangw wrote:
> > > 2. This is the second proposal:
> > > 
> > > Make the "pipeline_xrun_recover()" function atomic, which might avoid
> > > this kind of issue.
> > > 
> > 
> > This is what I suggested yesterday, including making the IPC initiated
> > pipeline
> > OPS atomic too.
> 
> But if the "pipeline_xrun_recover()" function has the higher priority 
> than IPC,
> do you think which event will preempt this function?

It could be preempted by another DMA IRQ, which would cause another XRUN by
updating pointers or changing state.


> 
> the IPC message process is this function: ipc_process_msg_queue().
> I think the IPC message receive and reply has serialized already.
> before the first message is not processed and replied, the second 
> message will
> not be received from HOST.
> maybe I misunderstand your meaning, could you point out the exact location?

The collision between IPC and pipeline ops could come from a pipeline IRQ when
processing an IPC message. This will be very rare, but can happen, hence the
need to make the pipeline IPC ops atomic.

Liam