linux-kernel - Re: [PATCH] of/platform: Fix no irq domain found errors when populating interrupts

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Message-ID: <20140411184306.GC3673@mithrandir>
Date:	Fri, 11 Apr 2014 20:43:07 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Rob Herring <robherring2@...il.com>
Cc:	Tony Lindgren <tony@...mide.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Grant Likely <grant.likely@...aro.org>,
	Paul Walmsley <paul@...an.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of/platform: Fix no irq domain found errors when
 populating interrupts

On Thu, Apr 10, 2014 at 07:29:36PM -0500, Rob Herring wrote:
> On Thu, Apr 10, 2014 at 4:38 PM, Tony Lindgren <tony@...mide.com> wrote:
> > Currently we get the following kind of errors if we try to use interrupt
> > phandles to irqchips that have not yet initialized:
> >
> > irq: no irq domain found for /ocp/pinmux@...02030 !
> > ------------[ cut here ]------------
> > WARNING: CPU: 0 PID: 1 at drivers/of/platform.c:171 of_device_alloc+0x144/0x184()
> > Modules linked in:
> > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.12.0-00038-g42a9708 #1012
> > (show_stack+0x14/0x1c)
> > (dump_stack+0x6c/0xa0)
> > (warn_slowpath_common+0x64/0x84)
> > (warn_slowpath_null+0x1c/0x24)
> > (of_device_alloc+0x144/0x184)
> > (of_platform_device_create_pdata+0x44/0x9c)
> > (of_platform_bus_create+0xd0/0x170)
> > (of_platform_bus_create+0x12c/0x170)
> > (of_platform_populate+0x60/0x98)
> >
> > This is because we're wrongly trying to populate resources that are not yet
> > available. It's perfectly valid to create irqchips dynamically, so let's
> > fix up the issue by populating the interrupt resources at the driver probe
> > time instead.
> >
> > Note that at least currently we cannot dynamically allocate the resources as bus
> > specific code may add legacy resources with platform_device_add_resources()
> > before the driver probe. At least omap_device_alloc() currently relies on
> > num_resources to determine if legacy resources should be added. Some of these
> > will clear automatically when mach-omap2 boots with DT only, but there are
> > probably other places too where platform_device_add_resources() modifies
> > things before driver probe.
> >
> > This patch was discussed quite a bit earlier, but so far it seems we don't
> > have any better options to fix the problem. For the earlier discussion,
> > please see:
> >
> > https://lkml.org/lkml/2013/11/22/520
> 
> There is a newer solution here which Grant seemed happier with:
> 
> http://lkml.iu.edu/hypermail/linux/kernel/1403.2/03666.html

I wonder why Grant seems to be happier with that solution than with my
original proposal. That new solution does essentially the same thing.
One of the main issues raised during review of my original proposal was
that it had to modify the core, but this new solution does that as well.

Another thing that people weren't happy about was that my solution was
more intrusive because it required a bunch of changes to the of_irq_*()
helpers to make them propagate a proper error code. The new solution
doesn't do that, but instead works around the lack of proper error
propagation by trying to find an IRQ domain (which the of_irq_*()
helpers will do anyway).

Thierry

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