Support for multiple MSI interrupts on MPC8377

Support for multiple MSI interrupts on MPC8377

[Giffel, Brad]

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I'm working a project using a Spartan 6 FPGA with a PCIe interface and
MSI interrupts.  I want to use multiple MSI interrupts (MSI-X is not
supported in the FPGA PCIe core) but the current Linux distribution
(3.0.8) prevents that (lines 23 to 25 in arch/powerpc/kernel/msi.c).

 

What's the story here?  Is the code in place but not tested?  I tried
commenting out those lines but a request_irq() called failed for the
second interrupt requested.  Am I wasting my time here?  Should I
re-architect to use a single MSI interrupt?

 

            Thanks,

            - Brad

 


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Re: Support for multiple MSI interrupts on MPC8377

[Michael Ellerman]

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On Wed, 2011-11-02 at 16:02 -0500, Giffel, Brad wrote:
> I’m working a project using a Spartan 6 FPGA with a PCIe interface and
> MSI interrupts.  I want to use multiple MSI interrupts (MSI-X is not
> supported in the FPGA PCIe core) but the current Linux distribution
> (3.0.8) prevents that (lines 23 to 25 in arch/powerpc/kernel/msi.c).
> 
>  
> 
> What’s the story here?  Is the code in place but not tested?  I tried
> commenting out those lines but a request_irq() called failed for the
> second interrupt requested.  Am I wasting my time here?  Should I
> re-architect to use a single MSI interrupt?

The short and easy answer is you should use a single MSI interrupt.

There is some code in place to support multiple MSI, but only in the
generic code (drivers/pci/msi.c), and I'm not sure if it's complete.
There is no arch support, for any arch AFAIK, and certainly not for
powerpc.

cheers



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RE: Support for multiple MSI interrupts on MPC8377

[Giffel, Brad]

A single MSI interrupt it is then.

	Thanks,
	- Brad


-----Original Message-----
From: Michael Ellerman [mailto:michael@ellerman.id.au]=20
Sent: Wednesday, November 02, 2011 10:51 PM
To: Giffel, Brad
Cc: linuxppc-dev@lists.ozlabs.org; Matthew Wilcox
Subject: Re: Support for multiple MSI interrupts on MPC8377

On Wed, 2011-11-02 at 16:02 -0500, Giffel, Brad wrote:
> I'm working a project using a Spartan 6 FPGA with a PCIe interface and
> MSI interrupts.  I want to use multiple MSI interrupts (MSI-X is not
> supported in the FPGA PCIe core) but the current Linux distribution
> (3.0.8) prevents that (lines 23 to 25 in arch/powerpc/kernel/msi.c).
>=20
> =20
>=20
> What's the story here?  Is the code in place but not tested?  I tried
> commenting out those lines but a request_irq() called failed for the
> second interrupt requested.  Am I wasting my time here?  Should I
> re-architect to use a single MSI interrupt?

The short and easy answer is you should use a single MSI interrupt.

There is some code in place to support multiple MSI, but only in the
generic code (drivers/pci/msi.c), and I'm not sure if it's complete.
There is no arch support, for any arch AFAIK, and certainly not for
powerpc.

cheers

Re: Support for multiple MSI interrupts on MPC8377

[Matthew Wilcox]

On Thu, Nov 03, 2011 at 02:51:22PM +1100, Michael Ellerman wrote:
> There is some code in place to support multiple MSI, but only in the
> generic code (drivers/pci/msi.c), and I'm not sure if it's complete.
> There is no arch support, for any arch AFAIK, and certainly not for
> powerpc.

I think there's an ARM or MIPS architecture that implements support for
it ... the x86 support was never merged.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."