linux-kernel - Re: next/mmotm unbootable on G5: irqdomain

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Date:	Mon, 23 Jul 2012 01:59:09 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Milton Miller <miltonm@....com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Rob Herring <rob.herring@...xeda.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: next/mmotm unbootable on G5: irqdomain

On Sun, Jul 22, 2012 at 8:45 PM, Benjamin Herrenschmidt
<benh@...nel.crashing.org> wrote:
> On Sat, 2012-07-21 at 19:47 -0700, Hugh Dickins wrote:
>> I have to revert the patch below from mmotm 2012-07-20-16-30 or
>> next-20120720 in order to boot on the PowerPC G5: otherwise it
>> freezes before switching to the framebuffer console - but I'm
>> not certain where because that initial console doesn't scroll
>> (there are mpic messages at bottom and at top of screen, probably
>> later messages at the top but I don't know the sequence).
>
> This fixes it (Grant, how do we avoid bisection breakage here ? I can
> put that in -powerpc and we can make sure that gets merged before your
> tree ?)

My tree must be rebased to eliminate bisect breakage. The existing
commits in my tree have the breakage, and fiddling with the merge
order doesn't affect that. I don't want to rebase though. The safest
approach (smallest window of breakage) is to apply that fix onto my
irqdomain tree.

g.

>
> powerpc/mpic: Create a revmap with enough entries for IPIs and timers
>
> The current mpic code creates a linear revmap just big enough for all
> the sources, which happens to miss the IPIs and timers on some machines.
>
> This will in turn break when the irqdomain code loses the fallback of
> doing a linear search when the revmap fails (and really slows down IPIs
> otherwise).
>
> This happens for example on the U4 based Apple machines such as the
> dual core PowerMac G5s.
>
> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> ---
> diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
> index 906f29c..bfc6211 100644
> --- a/arch/powerpc/sysdev/mpic.c
> +++ b/arch/powerpc/sysdev/mpic.c
> @@ -1376,7 +1376,7 @@ struct mpic * __init mpic_alloc(struct device_node *node,
>         mpic->isu_mask = (1 << mpic->isu_shift) - 1;
>
>         mpic->irqhost = irq_domain_add_linear(mpic->node,
> -                                      last_irq + 1,
> +                                      intvec_top,
>                                        &mpic_host_ops, mpic);
>
>         /*
>
>



-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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