Re: [PATCH v2 7/7] iio: adc: ad9467: support digital interface calibration

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 29 Apr 2024 09:24:21 +0200
Nuno Sá <noname.nuno@gmail.com> wrote:

> On Sun, 2024-04-28 at 18:32 +0100, Jonathan Cameron wrote:
> > On Fri, 26 Apr 2024 17:42:16 +0200
> > Nuno Sa via B4 Relay <devnull+nuno.sa.analog.com@kernel.org> wrote:
> >   
> > > From: Nuno Sa <nuno.sa@analog.com>
> > > 
> > > To make sure that we have the best timings on the serial data interface
> > > we should calibrate it. This means going through the device supported
> > > values and see for which ones we get a successful result. To do that, we
> > > use a prbs test pattern both in the IIO backend and in the frontend
> > > devices. Then for each of the test points we see if there are any
> > > errors. Note that the backend is responsible to look for those errors.
> > > 
> > > As calibrating the interface also requires that the data format is disabled
> > > (the one thing being done in ad9467_setup()), ad9467_setup() was removed
> > > and configuring the data fomat is now part of the calibration process.
> > > 
> > > Signed-off-by: Nuno Sa <nuno.sa@analog.com>  
> > 
> > One trivial comment.
> > 
> > I'd have picked up the whole series, but it feels too big to do on a Sunday
> > when you only posted on Friday.  Hence, lets let it sit for at least
> > a few more days to see if others have comments.  
> 
> Yeah, I kind of waited till the last moment to see if you had any important
> comment (on the first version open discussions) that could affect v2 :).
> > 
> > It might not make this cycle as a result.   I've picked up the 2 fixes
> > today to increase the chances those make it.
> > 
> > Jonathan
> > 
> >   
> > >  static int ad9467_read_raw(struct iio_dev *indio_dev,
> > >  			   struct iio_chan_spec const *chan,
> > >  			   int *val, int *val2, long m)
> > > @@ -345,7 +606,9 @@ static int ad9467_write_raw(struct iio_dev *indio_dev,
> > >  {
> > >  	struct ad9467_state *st = iio_priv(indio_dev);
> > >  	const struct ad9467_chip_info *info = st->info;
> > > +	unsigned long sample_rate;
> > >  	long r_clk;
> > > +	int ret;
> > >  
> > >  	switch (mask) {
> > >  	case IIO_CHAN_INFO_SCALE:
> > > @@ -358,7 +621,23 @@ static int ad9467_write_raw(struct iio_dev *indio_dev,
> > >  			return -EINVAL;
> > >  		}
> > >  
> > > -		return clk_set_rate(st->clk, r_clk);
> > > +		sample_rate = clk_get_rate(st->clk);
> > > +		/*
> > > +		 * clk_set_rate() would also do this but since we would
> > > still
> > > +		 * need it for avoiding an unnecessary calibration, do it
> > > now.
> > > +		 */
> > > +		if (sample_rate == r_clk)
> > > +			return 0;
> > > +
> > > +		iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
> > > +			ret = clk_set_rate(st->clk, r_clk);
> > > +			if (ret)
> > > +				return ret;
> > > +
> > > +			guard(mutex)(&st->lock);
> > > +			ret = ad9467_calibrate(st);  
> > 			return ad9467_calibrate(st);  
> > > +		}  
> > 		unreachable();
> > 
> > not totally elegant but I think the early return makes more sense and we
> > should
> > just use an unreachable() to squash the resulting compiler warning.
> >   
> 
> As you might remember I'm not a big fan of the unreachable() but also no strong
> feelings about it :). Do you expect a v3 for this or is this something you can
> fix up while applying (assuming no other things pop by)? 

I changed my mind and didn't bother adjusting this.

I've queued this up and pushed it out as testing on basis I can always drop
it again if reviews come in within the next 2-3 days, but in meantime I can
let 0-day have at it.

Jonathan

> 
> - Nuno Sá
> >