Hello Stephen,
On 16/09/2013 18:41, Stephen Warren wrote:
On 09/14/2013 01:08 AM, boris brezillon wrote:
Hello Stephen,
Le 14/09/2013 00:40, Stephen Warren a écrit :
On 09/13/2013 01:53 AM, Boris BREZILLON wrote:
AT91 SoCs do not support per pin debounce time configuration.
Instead you have to configure a debounce time which will be used for all
pins of a given bank (PIOA, PIOB, ...).
...
Required properties for pin configuration node:
...
-DEBOUNCE_VAL (0x3fff << 17): debounce val.
This change would break the DT ABI since it removes a feature that's
already present.
...
I suppose it's still up to the Atmel maintainers to decide whether this
is appropriate, or whether the impact to out-of-tree DT files would be
problematic.
Assuming the DT ABI can be broken, I think I'd prefer to do so, rather
than take "non-alt" patch 4/4, since a per-pin DEBOUNCE_VAL clearly
doesn't correctly model the HW, assuming the patch description is
correct. I don't think arguments re: the generic pinconf debounce
property hold; if the Linux-specific/internal generic property doesn't
apply, the DT binding should not be bent to adjust to it, but should
rather still represent the HW itself.
What about the last point in my list: "reconfigure debounce after
startup" ?
Here is an example that may be problematic:
Let's say you have one device using multiple configuration of pins
("default", "xxx", "yyy").
The "default" config needs a particular debounce time on a given pin and
the "xxx" and "yyy"
configs need different debounce time on the same pin.
How would you solve this with this patch approach ?
Each state has a different pin configuration node, and hence can specify
a different debounce value. This patch has no impact on that (it just
changes whether the state-specific node specifies the debounce value in
a single standalone property, or encodes it into each entry in the pins
property, all within the same node).
Actually it does: this patch removes the debounce time setting option from
the pin config description. The only thing you can do is enable or
disable the
debounce filter.
The atmel,default-debounce-div property is not part of the pin group (or
pin state)
node, it is a global property you define for the whole pinctrl
controller (pinctrl node
property):
pinctrl {
atmel,default-debounce-div=<100 /* PIOA div <=> ~3 ms */
50 /* PIOB
div */
...>;
function {
group {
atmel,pins=<...>;
};
};
};
I can get the debounce time option in a separate property (as you're
suggesting):
pinctrl {
function {
group {
atmel,debounce=<1000>; /* debounce in usec */
atmel,pins=<...>;
};
};
};
but it won't solve the primary issue, that is all the pin on a given
bank (PIOA1 PIOA2, ...)
share the same debounce time.
Please tell me if I misunderstood your suggestion.
Best Regards,
Boris
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