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

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Date:	Tue, 10 Feb 2015 11:19:39 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Geert Uytterhoeven <geert+renesas@...der.be>,
	Simon Horman <horms@...ge.net.au>,
	Magnus Damm <magnus.damm@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
	Thierry Reding <thierry.reding@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: shmobile: r8a73a4: Move pfc node to work around
 probe ordering bug

On Mon, Feb 9, 2015 at 7:29 PM, Tony Lindgren <tony@...mide.com> wrote:
> * Geert Uytterhoeven <geert@...ux-m68k.org> [150209 09:17]:
>> On Mon, Feb 9, 2015 at 5:24 PM, Tony Lindgren <tony@...mide.com> wrote:
>> > * Geert Uytterhoeven <geert+renesas@...der.be> [150206 12:26]:
>> >> 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.
>
> OK

I tried converting the renesas,irqc driver to IRQCHIP_DECLARE().
This solves the probe ordering problem, but it no longer allows the use of
a platform device. As I was already adding clock and runtime PM support
(which use platform devices), IRQCHIP_DECLARE doesn't look like the
right road to follow...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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
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