Re: [PATCH 5/6] soundwire: qcom: update register read/write routine

[Pierre-Louis Bossart]

> > > > > generates interrupt after it successfully finishes. This is really
> > > > > overhead, limiting and not really necessary unless we are doing
> > > > > something special.
> > > > >
> > > > > We can simply read/write the fifo that should also give exactly
> > > > > what we need! This will also allow to read/write registers in
> > > > > interrupt context, which was not possible with the special
> > > > > command approach.
> > > >
> > > > This is really unclear, sorry.
> > >
> > > If read/writes are waiting for an interrupt, it becomes difficult to 
> > > read or write to any registers from same interrupt handler!
> >
> > Well, yes, you need to handle the complete() at a lower level than the 
> > code that initiates the transactions otherwise you self-deadlock.
> >
> > IIRC in the Intel initial code, the complete was in the handler and 
> > the register IOs in the thread.
> Yes, we did the same in previous version of the code, however with this 
> patch reading/writing fifo directly without need of completion should 
> remove that need of another thread!

Right, but you'll also write-off some command/control efficiency by 
either sleeping too much before checking the status, or sleeping too 
little and reading status from a transaction that's not finished.