Message-ID: <CAFXKEHary=PcCh3GEEXznJQgcxj54ZmGR0jmzBdpx8ZVtk2_0g@mail.gmail.com>
Date: Mon, 21 Apr 2025 00:12:17 +0200
From: Lothar Rubusch <l.rubusch@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, eraretuya@...il.com
Subject: Re: [PATCH v6 09/11] iio: accel: adxl345: add inactivity feature

Happy Easter (again)!

On Fri, Apr 18, 2025 at 8:34 PM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Mon, 14 Apr 2025 18:42:43 +0000
> Lothar Rubusch <l.rubusch@...il.com> wrote:
>
> > Add the inactivity feature of the sensor. When activity and inactivity
> > are enabled, a link bit will be set linking activity and inactivity
> > handling. Additionally, the auto-sleep mode will be enabled. Due to the
> > link bit the sensor is going to auto-sleep when inactivity was
> > detected.
> >
> > Inactivity detection needs a threshold to be configured, and a time
> > after which it will go into inactivity state if measurements under
> > threshold.
> >
> > When a ODR is configured this time for inactivity is adjusted with a
> > corresponding reasonable default value, in order to have higher
> > frequencies and lower inactivity times, and lower sample frequency but
> > give more time until inactivity. Both with reasonable upper and lower
> > boundaries, since many of the sensor's features (e.g. auto-sleep) will
> > need to operate beween 12.5 Hz and 400 Hz. This is a default setting
> > when actively changing sample frequency, explicitly setting the time
> > until inactivity will overwrite the default.
> >
> > Similarly, setting the g-range will provide a default value for the
> > activity and inactivity thresholds. Both are implicit defaults, but
> > equally can be overwritten to be explicitly configured.
> >
> > Signed-off-by: Lothar Rubusch <l.rubusch@...il.com>
> Hi Lothar,
>
> Patches 6-8 look good to me.
>
> This runs into a similar issue to the freefall one. I haven't dug into
> the datasheet but does it report on one channel going inactive, or
> all being inactive at the same time?  I checked and it is the all
> case so we should be both on a pseudo channel to describe it right
> and reporting IIO_MOD_X_AND_Y_AND_Z not the OR form.
>
> Sorry again that I'm only realising this on v6 :(

No problem at all! Sure, I'm still in this phase where counting every
single commit upstream makes my ego greater. On the long run, though,
I guess it's better to build up knowledge and end up with a decent
implementation quality, than just increasing a commit counter. For me
it's fine. I also hope it's not too annoying for you.

>
> Difference is for Activity the definition is:
> "The activity bit is set when acceleration greater than the value
> stored in the THRESH_ACT register (Address 0x24) is experienced
> on _any_ participating axis, set by the ACT_INACT_CTL register
> (Address 0x27)."
> vs Inactivity:
> "The inactivity bit is set when acceleration of less than the value
> stored in the THRESH_INACT register (Address 0x25) is experienced
> for more time than is specified in the TIME_INACT
> register (Address 0x26) on _all_ participating axes, as set by the
> ACT_INACT_CTL register (Address 0x27). "
>
> So all vs any.
>

I think I  see your point. At least I change here for inactivity, too,
to AND'ed axis.

IMHO, if I set OR here, the first axis raising the inactivity will put
the sensor to sleep mode,
where AND needs all three axis in inactivity state. I'm not sure if
this works out, I need to verify
it still with the hardware, for now I'll change this to AND.

> > +
> > +/**
> > + * adxl345_set_inact_time_s - Configure inactivity time explicitly or by ODR.
> > + * @st: The sensor state instance.
> > + * @val_s: A desired time value, between 0 and 255.
> > + *
> > + * Inactivity time can be configured between 1 and 255 sec. If a val_s of 0
> > + * is configured by a user, then a default inactivity time will be computed.
> > + *
> > + * In such case, it should take power consumption into consideration. Thus it
> > + * shall be shorter for higher frequencies and longer for lower frequencies.
> > + * Hence, frequencies above 255 Hz shall default to 10 s and frequencies below
> > + * 10 Hz shall result in 255 s to detect inactivity.
> > + *
> > + * The approach simply subtracts the pre-decimal figure of the configured
> > + * sample frequency from 255 s to compute inactivity time [s]. Sub-Hz are thus
> > + * ignored in this estimation. The recommended ODRs for various features
> > + * (activity/inactivity, sleep modes, free fall, etc.) lie between 12.5 Hz and
> > + * 400 Hz, thus higher or lower frequencies will result in the boundary
> > + * defaults or need to be explicitly specified via val_s.
> > + *
> > + * Return: 0 or error value.
> > + */
> > +static int adxl345_set_inact_time_s(struct adxl345_state *st, u32 val_s)
> > +{
> > +     unsigned int max_boundary = 255;
> > +     unsigned int min_boundary = 10;
> > +     unsigned int val = min(val_s, max_boundary);
> > +     enum adxl345_odr odr;
> > +     unsigned int regval;
> > +     int ret;
> > +
> > +     if (val == 0) {
> > +             ret = regmap_read(st->regmap, ADXL345_REG_BW_RATE, &regval);
> > +             if (ret)
> > +                     return ret;
> > +             odr = FIELD_GET(ADXL345_BW_RATE_MSK, regval);
> > +
> > +             val = (adxl345_odr_tbl[odr][0] > max_boundary)
> > +                     ? min_boundary : max_boundary - adxl345_odr_tbl[odr][0];
> > +     }
> > +
> > +     return regmap_write(st->regmap, ADXL345_REG_TIME_INACT, val);
> >  }
> >
> >  /* tap */
> > @@ -837,6 +943,13 @@ static int adxl345_read_event_config(struct iio_dev *indio_dev,
> >                       if (ret)
> >                               return ret;
> >                       return int_en;
> > +             case IIO_EV_DIR_FALLING:
> > +                     ret = adxl345_is_act_inact_en(st, chan->channel2,
>
> Does it makes sense to allow inactivity detection on a subset of channels but then
> report it as XYZ?  I guess it didn't matter when it was and OR, but if we
> change to AND as suggested that is going to be misleading.
>
> we might have to allow separate enables but report an event as the combination
> of channels that are enabled X_AND_Y, X_AND_Z etc  I guess we can improve activity
> channel case as well by doing that with the X_OR_Y etc
>

Well, initially I guess I only had one enable for inactivity.

This was kind of confusing to me. There is a register to enable
activity and inactivity on a per axis base [ACT_INACT_CTL, 0x27].

The interrupt event will set a single bit for inactivity or activity
[INT_SOURCE, 0x30]. In the interrupt handler further one can read out
the [ACT_TAP_STATUS, 0x2B], which contains tap and activity
directions, but no information about inactivity axis.

In summary, for the ADXL345 inactivity can be configured on a per axis
base, but the event won't tell about the axis that fell into
inactivity, i.e. the first inactivity is supposed to put the sensor
into power save (with link bit and power modes set - I think
inactivity should mainly be seen in the context of their/Analog's
power save concept). As said before, initially I only provided a
single "inactivity enable". Then I saw actually I could set and offer
this per axis. I don't know if there are use cases only to observe
particularly the x-axis for a general power save. Probably rather not.

So, I agree. But if you don't tell me explicitely to replace per axis
enables by a single one, I'll probably leave it as is. It implements
most transparently what the sensor can offer for configuration.

>
>
> > +                                                   ADXL345_INACTIVITY,
> > +                                                   &int_en);
> > +                     if (ret)
> > +                             return ret;
> > +                     return int_en;
> >               default:
> >                       return -EINVAL;
> >               }
> > @@ -881,6 +994,9 @@ static int adxl345_write_event_config(struct iio_dev *indio_dev,
> >               case IIO_EV_DIR_RISING:
> >                       return adxl345_set_act_inact_en(st, chan->channel2,
> >                                                       ADXL345_ACTIVITY, state);
> > +             case IIO_EV_DIR_FALLING:
> > +                     return adxl345_set_act_inact_en(st, chan->channel2,
> > +                                                     ADXL345_INACTIVITY, state);
> >               default:
> >                       return -EINVAL;
> >               }
>
> > @@ -1314,6 +1458,17 @@ static int adxl345_push_event(struct iio_dev *indio_dev, int int_stat,
> >                       return ret;
> >       }
> >
> > +     if (FIELD_GET(ADXL345_INT_INACTIVITY, int_stat)) {
> > +             ret = iio_push_event(indio_dev,
> > +                                  IIO_MOD_EVENT_CODE(IIO_ACCEL, 0,
> > +                                                     IIO_MOD_X_OR_Y_OR_Z,
>
> So this is our open question. Similar to the free fall case. Do we have the boolean
> logic right way around?
>
> > +                                                     IIO_EV_TYPE_THRESH,
> > +                                                     IIO_EV_DIR_FALLING),
> > +                                  ts);
> > +             if (ret)
> > +                     return ret;
> > +     }
> > +

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