Re: [alsa-devel] [RFC PATCH 6/6] soundwire: qcom: add support for SoundWire controller

[Srinivas Kandagatla]

On 10/06/2019 15:12, Pierre-Louis Bossart wrote:
> > > > +
> > > > +ÂÂÂ if (dev_addr == SDW_BROADCAST_DEV_NUM) {
> > > > +ÂÂÂÂÂÂÂ ctrl->fifo_status = 0;
> > > > +ÂÂÂÂÂÂÂ ret = wait_for_completion_timeout(&ctrl->sp_cmd_comp,
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ msecs_to_jiffies(TIMEOUT_MS));
> > >
> > > This is odd. The SoundWire spec does not handle writes to a single 
> > > device or broadcast writes differently. I don't see a clear reason 
> > > why you would only timeout for a broadcast write.
> >
> > There is danger of blocking here without timeout.
>
> Right, and it's fine to add a timeout. The question is why add a timeout 
> *only* for a broadcast operation? It should be added for every 
> transaction IMO, unless you have a reason not to do so.

I did try this before, the issue is when we read/write registers from 
interrupt handler, these can be deadlocked as we will be interrupt 
handler waiting for another completion interrupt, which will never 
happen unless we return from the first interrupt.

thanks,
srini

> > >