Re: I2C OF IRQ parsing issue due to probe ordering

Laurent Pinchart
2014-10-30T12:15:37Z

Hi Ezequiel,

On Thursday 30 October 2014 08:58:28 Ezequiel Garcia wrote:
> On 10/25/2014 07:13 PM, Laurent Pinchart wrote:
> > Hello,
> >
> > I recently ran into an issue with the OF IRQ parsing code in the I2C core
> > (of_i2c_register_devices in drivers/i2c/i2c-core.c).
> >
> > My DT contains the following nodes.
> >
> > gpio1: gpio@e6051000 {
> > ...
> > #interrupt-cells = <2>;
> > interrupt-controller;
> > clocks = <&mstp9_clks R8A7790_CLK_GPIO1>;
> > };
> >
> > iic2: i2c@e6520000 {
> > #address-cells = <1>;
> > #size-cells = <0>;
> > ...
> > hdmi@39 {
> > compatible = "adi,adv7511w";
> > reg = <0x39>;
> > interrupt-parent = <&gpio1>;
> > interrupts = <15 IRQ_TYPE_EDGE_FALLING>;
> > ...
> > };
> > };
> >
> > mstp9_clks: mstp9_clks@e6150994 {
> > ...
> > };
> >
> > The i2c@e6520000 node is probed before the gpio@e6051000 node. The
> > of_i2c_register_devices() function tries to register all children,
> > including hdmi@39. It tries to parse and map the I2C client IRQ by
> > calling irq_of_parse_and_map(), which returns 0 as the interrupt
> > controller isn't probed yet. The adv7511 driver later probes the hdmi@39
> > device and gets client->irq set to 0.
> >
> > We can't control the probe order.
>
> Maybe I'm missing something, but I think your i2c adapter is probed with
> a subsys_initcall (as many other adapters). Otherwise, I can't see why
> it would be probed before the the gpio controller.
>
> I think this initcall is your problem. Have you tried just using
> platform_driver's probe?

My I2C controller driver uses module_platform_driver(). The reason why the
GPIO controller is probed later is because the GPIO requires a clock, and the
clock device is probed after the I2C controller, resulting in a deferred
probing the first time the GPIO controller is probed.

In the general case probe ordering can't be controlled, especially with DT. I
believe we thus need a generic solution.