[PATCH] ARM: shmobile: r8a73a4: Move pfc node to work around probe ordering bug

Hi Tony,

On Mon, Feb 9, 2015 at 5:24 PM, Tony Lindgren [off-list ref] wrote:

* Geert Uytterhoeven [off-list ref] [150206 12:26]:

quoted

Currently the pin function controller (which is also a GPIO controller)
is instantiated before the interrupt controllers due to the order in the
DTS. At that time, the irq domains for the interrupt controllers
referenced by its interrupts-extended property cannot be found yet:

    irq: no irq domain found for /interrupt-controller at e61c0000 !

Nevertheless, the core OF probing code ignores this failure, besides a
debug message that's not normally printed:

    not all legacy IRQ resources mapped for pfc

and continues initialization of the device. Then, the sh-pfc driver
cannot find any IRQ resources, and thinks no interrupts are available,
causing gpio-keys to fail later:

    gpio-keys keyboard: Unable to claim irq 0; error -22
    gpio-keys: probe of keyboard failed with error -22

Move the pin function controller node after the interrupt controller
nodes it references to work around the bug in the core OF probing code.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
Notes:
  - It seems several people tried to solve this in the core OF probing
    code before, but the final solution never went in?
  - This can be reproduced on other SoCs (e.g. sh73a0 and r8a7740) by
    moving their pfc nodes before their interrupt controller nodes.
  - This patch is against my working tree, so it doesn't apply to
    Simon's repository, but you get the idea....

No issues with the patch, but here are few comments on the core
reasons (without looking at the code in this case) that might help
fix similar issues.

In all the cases I've seen these errors are caused by non-standard
custom initcall levels for drivers like i2c bus. The real solution
is to initialize drivers later with standard module_init, and stop
the race to the bottom with custom initcall levels.

If there is legacy board specific platofrm init code that needs
i2c gpios early, that code can probably be moved to initialize
later on.

In this case no i2c is involved. The drivers for both pinctrl
(renesas,pfc-r8a73a4) and irqchip (renesas,irqc) are registered
at the same level:
  - postcore_initcall(sh_pfc_init);
  - postcore_initcall(irqc_init);
Hence the system uses the "natural" order from within the DTS,
and decided to instantiate the pfc before the irqchip.

Also, there should not be any need for custom driver initcall
levels from Linux generic framework point of view as for example
irqchip implementing drivers work just fine as a loadable module.

As long as no other device that's instantiated earlier references that
irqchip?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds