On 27/08/2013 08:16, boris brezillon :
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.
I am not in favor for this kind of complicated heuristic. Deglitch and
Debounce filters are different features in at91 (even if they pursuit
the same goal). So I do prefer to let the user choose which feature is
preferred for his application and add a different flag.
(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.
The question is: how much this "generic" pinconf is... well... generic!
And it is not a answer I can give.
On the other hand, if the "generic" is not going to overcome the native
pinctrl, I do not feel like switching to this at the cost of changing
the whole dtsi/dts entries that we already have.
So, it is more to Linus and Stephen to give us clues about this...
Bye,
--
Nicolas Ferre
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