On Thu, Jan 28, 2016 at 12:49:37PM +0100, Thomas Gleixner wrote:
On Thu, 28 Jan 2016, Brian Starkey wrote:
I've got a few devices on the same interrupt line. One driver does
Just for the record: When will hardware folks finally understand that shared
interrupt lines are a nightmare?
In general, agreed. In this case though I think they get some grace - my
devices are all in an FPGA which only has one interrupt line to the SoC.
something along these lines:
res = platform_get_resource(dev, IORESOURCE_IRQ, 0);
flags = (res->flags & IRQF_TRIGGER_MASK) | IRQF_SHARED;
request_irq(res->start, handler, flags, "name", dev);
This seems pretty reasonable. The problem is since 4a43d686fe33:
of/irq: Pass trigger type in IRQ resource flags[1]
the trigger type information from device-tree is in res->flags.
So when the other drivers don't pass in any flags, they fail the check
in __setup_irq().
Changing the former driver to remove the flags doesn't seem right, and
adding flags to the latter would imply adding flags to _every_ driver,
which is an awful lot to change - and I'm not sure it would be possible
and/or effective in all cases.
So that commit does:
r->flags = IORESOURCE_IRQ | irqd_get_trigger_type(irq_get_irq_data(irq));
which reads the current setting of the interrupt line.
Now we pass exactly that to request_irq(). So first irq_of_parse_and_map()
configures the interrupt type when mapping it and then hands in the same type
information when requesting the irq.
Right, there's some redundancy here.
I have no idea what the purpose of this is and the changelog of that commit is
completely useless, sigh!
I've cc'ed the author and the device tree folks. Perhaps are they able to
explain what this commit tries to 'fix'.
This 'fix' is what makes me hit the problem - but even without it I
think the problem still exists.
It seems like in principle two drivers ought to be able to do
request_irq(irq, handler, IRQF_SHARED | IRQF_TRIGGER_HIGH, ...);
and
request_irq(irq, handler, IRQF_SHARED, ...);
without the latter call failing. Or do you disagree?
-Brian
Thanks,
tglx
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