Date:	Mon, 20 Aug 2007 15:25:27 +0200
From:	"Xu Yang" <risingsunxy@...glemail.com>
To:	"Stefan Richter" <stefanr@...6.in-berlin.de>
Cc:	linux-kernel@...r.kernel.org,
	"Catalin Marinas" <catalin.marinas@....com>,
	"Russell King" <rmk+kernel@....linux.org.uk>
Subject: Re: warning in set_irq_chip, ARM port (was Re: bug information)

Hi guys,

I already tried to constrain the max_irq=64, then the warnings disappeared.

but now I got new problems.

as long as the program jump to the interrupt
routine(realview_timer_interrupt) of the timer0, the program can not
go further, it only toggles between the gic_* functions, such as
gic_ack_irq. gic_mask_irq, handle_level_irq, and so on.

do you have any idea where could be the problem?
Best regards,

Yang

2007/8/18, Stefan Richter <stefanr@...6.in-berlin.de>:
> Xu Yang wrote:
> > When I was porting kernel 2.6.19 to my realview_eb_mpcore system, I
> > got the following information.
> ...
> > does anyone know what does these information tell ? and where might be
> > the problem?
> ...
> > <5>Linux version 2.6.19-arm2 (risingsunxy@...alhost.localdomain) (gcc
> > version 4.2.0 20070413 (prerelease) (CodeSourcery Sourcery G++ Lite
> > 2007q1-21)) #13 SMP Wed Aug 15 19:10:52 CEST 2007
> > CPU: ARMv6-compatible processor [410fb022] revision 2 (ARMv6TEJ), cr=00c5387f
> > Machine: ARM-RealView EB
> ...
> > BUG: warning at kernel/irq/chip.c:95/set_irq_chip()
> > [<c001d338>] (dump_stack+0x0/0x14) from [<c005b6f8>] (set_irq_chip+0x30/0x94)
> > [<c005b6c8>] (set_irq_chip+0x0/0x94) from [<c000de88>]
> > (gic_dist_init+0x144/0x1a8)
> ...
> > Trying to set irq flags for IRQ128
> ...
>
> These log lines com from the WARN_ON macro at the indicated file, line,
> and function.  This is the function definition:
> http://lxr.free-electrons.com/source/kernel/irq/chip.c?v=2.6.19#083
>
> So, set_irq_chip(irq, chip) was called with irq >= NR_IRQS.
>
> According to your log, the kernel iterated over IRQs up to 255 but
> NR_IRQS, the total number of IRQs, is obviously defined as 128.  The
> call trace points to gic_dist_init as caller of set_irq_chip.
> http://lxr.free-electrons.com/source/arch/arm/common/gic.c?v=2.6.19#108
>
> Either the parameters used to calculate max_irq in gic_dist_init are
> wrong, or NR_IRQS is wrong, or gic_dist_init's loop over the
> set_irq_chip call is wrong.  I am not familiar with this architecture,
> but this looks suspicious to me:
>
>        /*
>         * The GIC only supports up to 1020 interrupt sources.
>         * Limit this to either the architected maximum, or the
>         * platform maximum.
>         */
>        if (max_irq > max(1020, NR_IRQS))
>                max_irq = max(1020, NR_IRQS);
>
> Shouldn't this be:
>
>        if (max_irq > min(1020, NR_IRQS))
>                max_irq = min(1020, NR_IRQS);
>
> On the other hand, gic_dist_init's loop over set_irq_chip has been
> changed in Linux 2.6.21 to work with multiple interrupt controllers by
> the following patch from Catalin Marinas:
> "The current implementation only assumes one GIC to be present in the
> system. However, there are platforms with more than one cascaded
> interrupt controllers (RealView/EB MPCore for example)."
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=b3a1bde4db9889feb116330bff21214811c940e4
>
> I think it would be best if you try again with linux-2.6.22.y (latest is
> 2.6.22.3) or 2.6.23-rcX (latest is 2.6.23-rc3).  If the bug is still
> there, report to the linux-arm-kernel@...ts.arm.linux.org.uk.  (You
> would need to subscribe at
> http://lists.arm.linux.org.uk/mailman/listinfo/linux-arm-kernel first.)
>
>
> A few side notes on getting started with kernel hacking:
>
> I found 'LXR' a very useful tool to examine the kernel sources.
> A similar tool but for offline use is 'cscope', which I often use via
> the nice GUI frontend 'kscope'.
>
> The commit which changed set_irq_chip can be found using the history
> links in gitweb
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=history;f=arch/arm/common/gic.c;h=0c89bd35e06fb495dbaddfe2796c6d88a28cea87;hb=HEAD
> or quicker and more precisely on a locally installed git repo via 'git
> blame' or with the GUI frontend qgit.  I actually used qgit in this case.
> --
> Stefan Richter
> -=====-=-=== =--- =--=-
> http://arcgraph.de/sr/
>
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