Re: [PATCH] iio: gts-helper: Fix division loop

[Matti Vaittinen]

On 2/4/24 15:49, Subhajit Ghosh wrote:
> Hi Matti,
> > > > > >   drivers/iio/industrialio-gts-helper.c | 5 ++---
> > > > > >   1 file changed, 2 insertions(+), 3 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/iio/industrialio-gts-helper.c 
> > > > > > b/drivers/iio/industrialio-gts-helper.c
> > > > > > index 7653261d2dc2..abcab2d38589 100644
> > > > > > --- a/drivers/iio/industrialio-gts-helper.c
> > > > > > +++ b/drivers/iio/industrialio-gts-helper.c
> > > > > > @@ -34,7 +34,7 @@
> > > > > >   static int iio_gts_get_gain(const u64 max, const u64 scale)
> > > > > >   {
> > > > > >       u64 full = max;
> > > > > > -    int tmp = 1;
> > > > > > +    int tmp = 0;
> > > > > >       if (scale > full || !scale)
> > > > > >           return -EINVAL;
> > > > > > @@ -48,8 +48,7 @@ static int iio_gts_get_gain(const u64 max, const 
> > > > > > u64 scale)
> > > > > >           tmp++;
> > > > > >       }
> > > > > > -    while (full > scale * (u64)tmp)
> > > > > > -        tmp++;
> > > > > > +    tmp += div64_u64(full, scale);
> > > > > >       return tmp;
> > > > > >   }
> > > > > >
> > > > > > base-commit: 2cc14f52aeb78ce3f29677c2de1f06c0e91471ab
> > > > Hi Matti,
> > > >
> > > > Your fix works beautifully with the latest version of apds9306 
> > > > driver which I am working on.
> > > > All available scale values can be set without any errors. Thank you.
> > >
> > > Thanks for testing Subhajit! Just to ensure we have no 
> > > miscommunication - did you test just this division fix, or the 
> > > rounding fix here:
> > > https://lore.kernel.org/lkml/37d3aa193e69577353d314e94463a08d488ddd8d.1701780964.git.mazziesaccount@xxxxxxxxx/
> > You are most welcome. I did not check the above rounding fix pointed 
> > out by the link. I will be happy to check it and let you know by the 
> > end of this month.
> > I checked this division fix.
> I tested the patch in the above link with adps9306 driver which I am 
> working on and it seems to work well without any issues.

Great! Thanks a lot Subhajit! Your testing is very much appreciated :)

I think you sent another version of your APDS9306 driver. AFAIR, this 
driver could have benefited from the above rounding fix. I will see if I 
find the time and energy to see if I can dive into this again and 
re-spin this rounding fix. No promises but I'll try :)

Yours,
	-- Matti

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

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