On Thu, 23 Jul 2020 15:15:46 +0300 Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote: > On Wed, Jul 22, 2020 at 6:53 PM Jonathan Cameron <jic23@xxxxxxxxxx> wrote: > > > > From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > > > > We should not be assuming that we are reading a sequence of > > registers as here we are doing a read of a lot of data from > > a single register address. > > > - result = regmap_bulk_read(st->map, st->reg->fifo_r_w, > > - st->data, bytes_per_datum); > > + result = regmap_noinc_read(st->map, st->reg->fifo_r_w, > > + st->data, bytes_per_datum); > > I don't know the difference between these APIs, but AFAIU in this case > we always ask for a minimum data (like one item of 2 bytes or so) per > access. Because registers are defined like 16-bit wide we are fine. Is > that correct? Yes. There is only really a different in these two APIs if caching is enabled in regmap. Conceptually noinc is repeated reading of the same register, whilst build_read reads a bunch of registers starting at this location. If any of them happen to be cacheable, regmap_bulk_read will update the cached value for any registers it happens to read. In this particular case that would be incorrect because the hardware is not doing any auto increment of the address during repeated reads, it's just reading the same register lots of times. Jonathan
