Re: [PATCH v5] iio: accel: mma8452: improvements to handle multiple events

[Martin Kepplinger]

Am 10. September 2017 15:44:24 MESZ schrieb Jonathan Cameron <jic23@xxxxxxxxxx>:
>On Mon, 4 Sep 2017 23:06:37 -0400
>harinath Nampally <harinath922@xxxxxxxxx> wrote:
>
>> > I agree with your understanding.  It's a rising threshold, just
>that the input
>> > will only reflect high frequency changes in the signal.  
>> Thank you for the clarification. I am hoping this gets merged in the
>> next window if no other issues.
>
>There is still the open question to Martin on what he meant in his
>review to be addressed.
>
>Martin, any comments on this?
>
>I'm really looking for an OK from Martin before I take this one.
>Plenty of time though given the merge window is still open!

I had a look at v6 of this.

>
>I'm travelling this week so response may be a bit random depending
>on conference wifi and how interesting the material is ;)

enjoy,

    martin

>
>Jonathan
>
>> 
>> Thanks,
>> Hari
>> 
>> On Sun, Sep 3, 2017 at 12:24 PM, Jonathan Cameron <jic23@xxxxxxxxxx>
>wrote:
>> > On Tue, 29 Aug 2017 23:01:16 -0400
>> > harinath Nampally <harinath922@xxxxxxxxx> wrote:
>> >  
>> >> > We should never say "transient is for rising
>> >> > direction" or "ff_mt is for falling direction". any combination
>is fine.  
>> >>
>> >> Ok I agree that there is no hard and fast rule that "transient is
>for rising
>> >> direction" or "ff_mt is for falling direction".
>> >> But in our case, datasheet for these chips define these events
>based on
>> >> acceleration magnitude rising or falling below a set threshold
>value.
>> >>
>> >> For quick reference, below excerpts are from fxls8471 datasheet:
>> >> Motion Event: "When the acceleration exceeds a set threshold for a
>set
>> >> amount of time,
>> >> the motion interrupt is asserted."
>> >>
>> >> Freefall event: "The detection of âFreefallâ involves the
>monitoring
>> >> of the X, Y, and Z axes
>> >> for the condition where the acceleration magnitude is below a
>> >> user-specified threshold
>> >> for a user-definable amount of time"
>> >>
>> >> Transient event: "When the high-pass filter is bypassed, the
>> >> functionality becomes
>> >> similar to the motion-detection function; in this mode,
>acceleration
>> >> greater than
>> >> a programmable threshold is detected (along an axis)."
>> >>
>> >> Therefore I think in this driver freefall event is defined as
>> >> 'falling' event type and
>> >> motion event is defined as 'rising' event type and Transient is
>also defined as
>> >> 'rising' event type.
>> >>  As you might already know that mma8562 and mma8563 doesn't have
>> >> transient event support
>> >> but they do have freefall and motion event support which are
>defined
>> >> as 'fall' and 'rise'
>> >> event types respectively. Please note in this driver, motion event
>is
>> >> enabled/configured only
>> >> for mma8652 and mma8653.
>> >> Therefore if I read/write sysfs node for 'rise' it should use the
>> >> FF_MT registers for mma8652 and mma853, but for all others like
>> >> mma8451, mma8452 and
>> >> mma8453 which has transient event support it picks the Transient
>> >> registers if enabled. Also please
>> >> note transient event is enabled(but not motion event) for mma8451,
>> >> mma8452 and mma8453.
>> >> The problem seems like we have two different events(motion and
>> >> transient) that are defined
>> >> as same event type 'rising' but in fact both motion and transient
>are
>> >> pretty much similar as they
>> >> both raise interrupt flag when the acceleration magnitude rises
>above
>> >> the threshold.
>> >> Only difference is transient event has its own event config
>registers
>> >> with High pass filter.
>> >> If HPF bypassed using config register transient event acts like
>motion
>> >> detection event.  
>> >  
>> >>
>> >> That was my understanding but please correct me if I am wrong.  
>> >
>> > I agree with your understanding.  It's a rising threshold, just
>that the input
>> > will only reflect high frequency changes in the signal.
>> >  
>> >>  
>> >> > Only freefall mode needs one fix: remembering to which set of
>registers to fall back when
>> >> > disabling it.  
>> >>
>> >> I don't quite understand what you mean by 'to fall back when
>disabling
>> >> it'. Please elaborate. I would
>> >> appreciate if you could suggest your logic in the form of
>pseudo-code.
>> >> Thanks for your time
>> >>  
>> > ...  

-- 
Martin Kepplinger
http://martinkepplinger.com
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