LinuxQuestions.org - spport multiple MSI for pci device on Nehalem architecture

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- - spport multiple MSI for pci device on Nehalem architecture (https://www.linuxquestions.org/questions/linux-kernel-70/spport-multiple-msi-for-pci-device-on-nehalem-architecture-767863/)

spport multiple MSI for pci device on Nehalem architecture

I'm implementing a driver for a costum pci-device which supports 32 message signaled interrupts(MSIs) (the configuration space shows this). The device will be used on platform with a intel E5540 and tylersburg chipset. Kernel 2.6.30.5 is used at the moment.

To enable multiple msi i use pci_enable_msi_block(device,32); to try to enable 32 MSIs. This function returns 1, meaning i could only register one, and indeed when i try to register one interrupt it succeeds.

Trying to find the error i came accros the following piece of code in the kernel.

Code:

drivers/pci/msi.c:

 37 #ifndef arch_setup_msi_irqs

 38 int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)

 39 {

 40    struct msi_desc *entry;

 41    int ret;

 42

 43    /*

 44      * If an architecture wants to support multiple MSI, it needs to

 45      * override arch_setup_msi_irqs()

 46      */

 47    if (type == PCI_CAP_ID_MSI && nvec > 1)

 48        return 1;

 49

 50    list_for_each_entry(entry, &dev->msi_list, list) {

 51        ret = arch_setup_msi_irq(dev, entry);

 52        if (ret < 0)

 53            return ret;

 54        if (ret > 0)

 55            return -ENOSPC;

 56    }

 57

 58    return 0;

 59 }

 60 #endif

This states, it will always return 1, if the number of vectors is greater then 1? And an architecture should override this function to support multiple MSI? I can't realy find were and if this function is overwritten for my architecture (Intel Nehalem).

So my question is, how can multiple MSIs be aquired for my device.
NOTE: my device does not support MSI-X so this can't be used.

Kind Regards,

Rob

Quote:

Code:

 43    /*

 44      * If an architecture wants to support multiple MSI, it needs to

 45      * override arch_setup_msi_irqs()

 46      */

 47    if (type == PCI_CAP_ID_MSI && nvec > 1)

 48        return 1;

Yes. Yes. A simple grep could have told you that your architecture is "x86" and that this function is overridden in arch/x86/kernel/apic/io_apic.c.

The x86-specific code looks like this:

Code:

        /* x86 doesn't support multiple MSI yet */

        if (type == PCI_CAP_ID_MSI && nvec > 1)

                return 1;

Is it possible to adjust this code to support multiple MSI on the Nehalem architecture?

If so, how should i proceed?

Kind regards,

robvoo

Quote:

Is it possible to adjust this code to support multiple MSI on the Nehalem architecture?

Probably.

Quote:

If so, how should i proceed?

Write that support code.

Hi,

I have face the same problem now that add the code for support multiple MSI for X86 architecture.
Please Give some help for how to proceed.

Thanks in advance.