Re: [PATCH v2 1/3] spi: spi-mem: add automatic poll status functions

[Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>]

On Mon, 10 May 2021 10:46:48 +0200
Patrice CHOTARD <patrice.chotard@xxxxxxxxxxx> wrote:

> >   
> >> +
> >> +	if (ctlr->mem_ops && ctlr->mem_ops->poll_status) {
> >> +		ret = spi_mem_access_start(mem);
> >> +		if (ret)
> >> +			return ret;
> >> +
> >> +		reinit_completion(&ctlr->xfer_completion);
> >> +
> >> +		ret = ctlr->mem_ops->poll_status(mem, op, mask, match,
> >> +						 timeout_ms);
> >> +
> >> +		ms = wait_for_completion_timeout(&ctlr->xfer_completion,
> >> +						 msecs_to_jiffies(timeout_ms));  
> > 
> > Why do you need to wait here? I'd expect the poll_status to take care
> > of this wait.  
> 
> It was a request from Mark Brown [1]. The idea is to implement
> similar mechanism already used in SPI framework.

Well, you have to choose, either you pass a timeout to ->poll_status()
and let the driver wait for the status change (and return -ETIMEDOUT if
it didn't happen in time), or you do it here and the driver only has to
signal the core completion object. I think it's preferable to let the
driver handle the timeout though, because you don't know how the
status check will be implemented, and it's not like the
reinit_completion()+wait_for_completion_timeout() done here would
greatly simplify the drivers wait logic anyway.