Re: [PATCH v2] iio: sx9310: Fix semtech,avg-pos-strength setting when > 16

[Jonathan Cameron <jic23@kernel.org>]

On Sat, 21 Nov 2020 14:58:49 +0000
Jonathan Cameron <jic23@kernel.org> wrote:

> On Fri, 20 Nov 2020 10:29:44 -0800
> Stephen Boyd <swboyd@chromium.org> wrote:
> 
> > This DT property can be 0, 16, and then 64, but not 32. The math here
> > doesn't recognize this slight bump in the power of 2 numbers and
> > translates a DT property of 64 into the register value '3' when it
> > really should be '2'. Fix it by subtracting one more if the number being
> > translated is larger than 16.
> > 
> > Cc: Daniel Campello <campello@chromium.org>
> > Cc: Lars-Peter Clausen <lars@metafoo.de>
> > Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
> > Cc: Douglas Anderson <dianders@chromium.org>
> > Cc: Gwendal Grignou <gwendal@chromium.org>
> > Cc: Evan Green <evgreen@chromium.org>
> > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> > ---
> > 
> > Changes from v1 (https://lore.kernel.org/r/20201120073842.3232458-1-swboyd@chromium.org):
> >  * Changed ternary to consider 17 to 31 as the same as 16
> > 
> >  drivers/iio/proximity/sx9310.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iio/proximity/sx9310.c b/drivers/iio/proximity/sx9310.c
> > index a2f820997afc..ee1b4ff05a37 100644
> > --- a/drivers/iio/proximity/sx9310.c
> > +++ b/drivers/iio/proximity/sx9310.c
> > @@ -1305,7 +1305,7 @@ sx9310_get_default_reg(struct sx9310_data *data, int i,
> >  		if (ret)
> >  			break;
> >  
> > -		pos = min(max(ilog2(pos), 3), 10) - 3;
> > +		pos = min(max(ilog2(pos), 3), 11) - (pos >= 32 ? 4 : 3);  
> 
> Given this is now rather tricky to read, I'd just do an explicit lookup of
> the allowed values.  Probably just a switch statement.
As an alternative, a comment would help saying that it's powers of 2 except
for a gap at 64.

Thanks,

J

> 
> Thanks,
> 
> Jonathan
> 
> >  		reg_def->def &= ~SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK;
> >  		reg_def->def |= FIELD_PREP(SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK,
> >  					   pos);
> > 
> > base-commit: 5b19ca2c78a0838976064c0347e46a2c859b541d  
>