Hi Stephan,
On 11/11/2013 07:53 PM, Stephen Warren wrote:
On 11/11/2013 11:28 AM, Gerlando Falauto wrote:
Hi everyone,
[jumping in on an old discussion]
On 09/09/2013 06:19 PM, Mark Brown wrote:
On Wed, Sep 04, 2013 at 02:16:36PM -0600, Stephen Warren wrote:
On 09/04/2013 03:05 AM, Lars Poeschel wrote:
The driver that tries to use the GPIO requested by this patch before
HAS to
fail. This is exactly the intention of this patch. We don't want the
GPIO to
be requested any more, if it is used as an interrupt pin.
That will break existing drivers. There are drivers that request the
same GPIO and IRQ. IIRC, the SDHCI CD (Card Detect) GPIO is requested
that way.
Yes, plus input devices and audio jack detection among others. This
pattern is very common if the GPIO is actually being used as a GPIO, an
edge triggered interrupt is used to flag when something happens and the
state is determined by reading the GPIO state (often with some
debounce).
I actually came across this thread while looking for an answer to the
following (apparently trivial) question:
If you were to write a new driver & binding, what would be, in general,
the recommended DT binding for a cascade interrupt controller (or any
other peripheral, for that matter), which is connected through a GPIO
(to be used as IRQ)?
a) Through gpios = <&gpio0 N>
b) through interrupt-parent = <&gpio0> & interrupts <N
IRQ_TYPE_LEVEL_LOW>, or
c) both?
(b) alone.
From the perspective of the child interrupt controller, its output is
purely an interrupt. The fact that the parent interrupt controller could
use that pin as a GPIO in some other context (e.g. on a different board)
isn't something that the child interrupt controller should know/care about.
Thanks for your answer. So it should be the parent driver to proactively
configure the GPIO as input, active high etc..., when an IRQ for its
GPIOs is requested, right?
Moving to a different target (actually Mark's original point), i.e. a
generic device which is connected through a GPIO, using the IRQ to
trigger an event, what would be the recommended way?
Thanks again!
Gerlando
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