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    SubjectRe: [RFC PATCH 1/3] pinctrl: add new generic pinconf config for deglitch filter
    On 27/08/2013 05:55, Stephen Warren wrote:
    > On 08/26/2013 11:01 AM, boris brezillon wrote:
    >> Hello Stephen,
    >>
    >> On 26/08/2013 18:50, Stephen Warren wrote:
    >>> On 08/24/2013 03:35 PM, Boris BREZILLON wrote:
    >>>> Add a new parameter to support deglitch filter configuration.
    >>>> A deglitch filter works like a debounce filter but with a smaller
    >>>> delay (nanoseconds).
    >>> Why not use the existing debounce property, just with a small delay
    >>> specified. It seems like that's exactly what the property is for?
    >> That's one of the question I asked in my cover letter :-)
    >>
    >> Indeed the at91 deglitch filter delay is not configurable and is statically
    >> assigned to half a master clk cycle (if master clk = 133MHz -> 8 ns).
    >> The debounce property argument is currently expressed in usecs.
    >>
    >> This will result in always selecting the debounce filter (which is also
    >> available on at91 SoCs) over the deglitch filter.
    >>
    >> Could we add a flag in the deglitch argument to specify the delay unit
    >> (nsecs or usecs) ?
    > If the value is hard-coded in HW, why not use non-zero (or 1) to enable
    > and zero to disable?

    Indeed at91 pins support both deglitch and debounce filter and I have to
    choose
    between the two given the argument value (in usec).

    Here's what I can do:

    if (arg >= 1/2 * slowclock) /* debounce case */
    /* choose debounce filter and configure the delay
    according to the given argument value */
    else /* deglitch case */
    /* choose deglitch filter */


    Slow clock is running at 32KHz which gives a 30 usec clock cycle.

    >
    > (this kind of thing is why I'm not convinced that generic pinconf works
    > so well... What if we need psecs in the future?)

    Should I keep the at91 native pinconf binding and add the missing flags
    to this binding
    (OUTPUT configuration flags) ?

    This was another question I asked in my cover letter: wether or not the
    generic pinconf
    binding should be used.



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