On Mon, Feb 11, 2013 at 07:31:00AM +0200, Baruch Siach wrote:
> Hi lkml,
Hi Baruch,
> The drivers/edac/mpc85xx_edac.c driver contains the following (abbreviated)
> code snippet it its .probe:
You dropped an important detail which is the preceeding line:
pdata->irq = irq_of_parse_and_map(op->dev.of_node, 0);
> res = devm_request_irq(&op->dev, pdata->irq,
> mpc85xx_pci_isr, IRQF_DISABLED,
> "[EDAC] PCI err", pci);
> if (res < 0) {
> irq_dispose_mapping(pdata->irq);
> goto err2;
> }
>
> Now, since the requested irq is already in use, and IRQF_SHARED is not set,
> devm_request_irq errors() out, which is OK. Less OK is the
> irq_dispose_mapping() call, which gives me this:
>
> EDAC PCI1: Giving out device to module 'MPC85xx_edac' controller
> 'mpc85xx_pci_err': DEV 'ffe0a000.pcie' (INTERRUPT)
> genirq: Flags mismatch irq 16. 00000020 ([EDAC] PCI err) vs. 00000020 ([EDAC]
> PCI err)
The hint here is to notice which other irq you're clashing with ^^
ie. yourself. Which is odd, that is the root of the problem.
The badness you're getting from irq_dispose_mapping() is caused because you're
disposing of that mapping which is currently still in use, by the same
interrupt.
That is caused by a "feature" in the irq mapping code, where if you ask to map
an
already mapped hwirq, it will give you back the same virq. So in your case when
you called irq_of_parse_and_map() it noticed that someone had already mapped
that hwirq, and gave you back an existing (in use) virq.
> mpc85xx_pci_err_probe: Unable to requiest irq 16 for MPC85xx PCI err
^
While you're there, can you fix the typo :)
> So, is irq_dispose_mapping() the right thing to do when irq request fails?
It's the right thing to do to undo the effect of irq_create_mapping(), or in
your case irq_of_parse_and_map().
It just falls down in this case, because you're inadvertently disposing of
something that's still in use.
> A simple grep shows that irq_dispose_mapping() calls are mostly limited to
> powerpc code. Is there a reason for that?
That's because the irq domain code began life as powerpc specific code. It's
now become generic and will start to appear in more places.
cheers
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