linux-kernel - Re: [PATCH v10 6/7] iio: accel: adxl345: extend inactivity time for less than 1s

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Message-ID: <aFpV1f1qapCQunVO@smile.fi.intel.com>
Date: Tue, 24 Jun 2025 10:37:57 +0300
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Lothar Rubusch <l.rubusch@...il.com>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org,
	dlechner@...libre.com, nuno.sa@...log.com, andy@...nel.org,
	corbet@....net, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	eraretuya@...il.com
Subject: Re: [PATCH v10 6/7] iio: accel: adxl345: extend inactivity time for
 less than 1s

On Mon, Jun 23, 2025 at 11:21:01PM +0200, Lothar Rubusch wrote:
> On Mon, Jun 23, 2025 at 12:17 PM Andy Shevchenko
> <andriy.shevchenko@...el.com> wrote:
> > On Sun, Jun 22, 2025 at 03:50:09PM +0000, Lothar Rubusch wrote:

...

> > > -static int adxl345_set_inact_time(struct adxl345_state *st, u32 val_s)
> > > +static int adxl345_set_inact_time(struct adxl345_state *st, u32 val_int,
> > > +                               u32 val_fract)
> > >  {
> > >       int max_boundary = U8_MAX;
> > >       int min_boundary = 10;
> > > -     unsigned int val = min(val_s, U8_MAX);
> > > +     unsigned int val;
> >
> > You see, I even suggested splitting this assignment to begin with.
> > The change will be clearer with that done.
> >
> > >       enum adxl345_odr odr;
> > >       unsigned int regval;
> > >       int ret;
> > >
> > > -     if (val == 0) {
> > > +     if (val_int == 0 && val_fract == 0) {
> 
> The case for 0sec, 0.0 or setting "0" and fract will consequently be
> "0". 0 is an invalid input for this period and sensor, so it will
> default to an optimized period based on given ODR.
> 
> > > +             /* Generated inactivity time based on ODR */
> > >               ret = regmap_read(st->regmap, ADXL345_REG_BW_RATE, &regval);
> > >               if (ret)
> > >                       return ret;
> >
> > >               odr = FIELD_GET(ADXL345_BW_RATE_MSK, regval);
> > >               val = clamp(max_boundary - adxl345_odr_tbl[odr][0],
> > >                           min_boundary, max_boundary);
> > > +             st->inact_time_ms = MILLI * val;
> > > +
> > > +             /* Inactivity time in s */
> > > +             return regmap_write(st->regmap, ADXL345_REG_TIME_INACT, val);
> > > +     } else if (val_int == 0 && val_fract > 0) {
> >
> > val_fract check is not needed here.
> 
> Case for e.g. 0.123, numbers under 1s. This goes into the free-fall register.

0.0 is already checked above, and since the val_fract is unsigned this is check
is redundant.

> > > +             /* time < 1s, free-fall */
> > > +
> > > +             /*
> > > +              * Datasheet max. value is 255 * 5000 us = 1.275000 seconds.
> > > +              *
> > > +              * Recommended values between 100ms and 350ms (0x14 to 0x46)
> > > +              */
> > > +             st->inact_time_ms = DIV_ROUND_UP(val_fract, MILLI);
> > > +
> > > +             return regmap_write(st->regmap, ADXL345_REG_TIME_FF,
> > > +                                 DIV_ROUND_CLOSEST(val_fract, 5));
> > > +     } else if (val_int > 0) {
> >
> > if now is redundant here, right?
> 
> So, this will be 1s through 255s. Periods above 1sec. This goes into
> the inactivity register.

See above,

> > > +             /* Time >= 1s, inactivity */
> > > +             st->inact_time_ms = MILLI * val_int;
> > > +
> > > +             return regmap_write(st->regmap, ADXL345_REG_TIME_INACT, val_int);
> > >       }
> > >
> > > -     return regmap_write(st->regmap, ADXL345_REG_TIME_INACT, val);
> > > +     /* Do not support negative or wrong input. */
> > > +     return -EINVAL;
> > >  }

-- 
With Best Regards,
Andy Shevchenko