Does gpio_to_irq() work for MPC52xx gpios?

Bill Gatliff bgat at
Thu Dec 24 16:38:11 EST 2009


Ok, I have gpio_to_irq() more-or-less showing signs of life for the
MPC5200.  But I'm having some trouble using it the way I want to.

Recall that I have a rotary encoder that's tied to IRQ2 and
GPIO_WKUP_7.  I want to be able to describe it something like this:

    rotary-encoder {
        compatible = "linux,rotary-encoder","rotary-encoder";
        interrupts = <&mpc5200_pic 2 3 &gpio_wkup 0 1>; // "IRQ2 on the
MPC5200 PIC,
// and pin 0 on GPIO_WKUP"
        type = <1>; // what event signal to generate
        val-ccw = <0x4a>; // what code to use for counter-clockwise rotation
        val-cw = <78>; // what code to use for clockwise rotation

I've had some limited success with this, but not for any good reason. 
It turns out that the explanation for why I was getting a valid number
for the first interrupt specification was because the device tree
compiler was assuming that the interrupt-parent was the mpc5200_pic; my
reference to the node in that list was utterly meaningless.  The dtc
also appears to have ignored the &gpio_wkup word, and interpreted the
following zero as being the zero-th interrupt channel in the
mpc5200_pic.  Or something like that.  Clearly, I don't understand the
device tree syntax at all yet.

Anyway, when I change the statement to this:

    rotary-encoder {
        compatible = "linux,rotary-encoder","rotary-encoder";
        interrupt-parent = <&gpio_wkup>;
        interrupts = <0 0>;
        type = <1>;
        val-ccw = <0x4a>;
        val-cw = <78>;

... then the magic number that the dtc comes up with is causing my new
chained interrupt handler for the gpio_wkup peripheral to come alive. 
(Of course it doesn't actually work yet, but that's not the point!)

So here's my question: does the device tree compiler/syntax limit you to
only one interrupt parent?

I think the answer is no, because what I'm trying to do doesn't seem
that much different from how one specifies GPIO pins coming from
different controllers.

Any suggestions?


Bill Gatliff
bgat at

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