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    SubjectRe: MSI messages
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    Date
    On Mon, 2008-12-22 at 02:56 +0400, Manu Abraham wrote:
    > Michael Ellerman wrote:
    > > On Sun, 2008-12-21 at 01:13 +0400, Manu Abraham wrote:
    > >> Grant Grundler wrote:
    > >>> On Sun, Dec 14, 2008 at 03:15:15PM +0400, Manu Abraham wrote:
    > >>> ...
    > >>>>> A "GSI" (Generic Sys Interrupt?) is associated with each entry in
    > >>>>> the MSI-X table. Driver then calls request_irq() to bind an interrupt
    > >>>>> handler to each GSI. So the driver never directly sees the "message".
    > >>>> Oh, you mean the array of irq_handlers in the MSI-X table should
    > >>>> correspond to a particular message ?
    > >>> No. I mean each MSI-X entry has an address+message pair and each MSI-X entry
    > >>> is associated with the parameters passed to each call of request_irq().
    > >>> Pass in unique private data to each call of request_irq() and the driver
    > >>> can determine which message was delivered when the ISR gets called.
    > >>> (ISR == Interrupt Service Routine, aka driver IRQ handler)
    > >>
    > >> Is it possible that even when the config space says that multiple messages
    > >> are supported, you cannot enable MSI-X ?
    > >
    > > Yes, absolutely. Have a look at pci_msi_check_device() for starters. MSI
    > > can be disabled globally, or per-device by a quirk, the bridges above
    > > your device might not support MSI and the arch code may prevent
    > > MSI/MSI-X for some reason (ie. platform doesn't support it).
    > >
    > > There's also a check in pci_enable_msix() to make sure the entries you
    > > pass in are valid.
    > >
    > >> ------------- with MSI-X -------------
    > >>
    > >> saa716x_pci_init (0): found a NEMO reference board PCIe card
    > >> ACPI: PCI Interrupt 0000:05:00.0[A] -> GSI 19 (level, low) -> IRQ 19
    > >> PCI: Setting latency timer of device 0000:05:00.0 to 64
    > >> saa716x_request_irq (0): Using MSI-X mode
    > >> saa716x_enable_msix (0): MSI-X request failed
    > >
    > > For starters you should print the error code returned by
    > > pci_enable_msix() - unfortunately it returns EINVAL for many different
    > > reasons, but it will narrow it down a bit.
    >
    > It does return -22

    If you're curious you could try this patch.

    >From bd27f10c9acd24bb849d14b6fc373444322c7405 Mon Sep 17 00:00:00 2001
    From: Michael Ellerman <michael@ellerman.id.au>
    Date: Mon, 22 Dec 2008 10:21:27 +1100
    Subject: [PATCH] MSI debug

    ---
    drivers/pci/msi.c | 52 ++++++++++++++++++++++++++++++++++++++++------------
    1 files changed, 40 insertions(+), 12 deletions(-)

    diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
    index 74801f7..575cca9 100644
    --- a/drivers/pci/msi.c
    +++ b/drivers/pci/msi.c
    @@ -517,17 +517,26 @@ static int pci_msi_check_device(struct pci_dev* dev, int nvec, int type)
    struct pci_bus *bus;
    int ret;

    + if (!dev) {
    + printk(KERN_DEBUG, "MSI: null device\n");
    + return -ENODEV;
    + }
    +
    /* MSI must be globally enabled and supported by the device */
    - if (!pci_msi_enable || !dev || dev->no_msi)
    + if (!pci_msi_enable || dev->no_msi)
    + dev_printk(KERN_DEBUG, &dev->dev, "MSI: MSI disabled\n");
    return -EINVAL;
    + }

    /*
    * You can't ask to have 0 or less MSIs configured.
    * a) it's stupid ..
    * b) the list manipulation code assumes nvec >= 1.
    */
    - if (nvec < 1)
    + if (nvec < 1) {
    + dev_printk(KERN_DEBUG, &dev->dev, "MSI: < 1 MSI requested\n");
    return -ERANGE;
    + }

    /* Any bridge which does NOT route MSI transactions from it's
    * secondary bus to it's primary bus must set NO_MSI flag on
    @@ -535,16 +544,24 @@ static int pci_msi_check_device(struct pci_dev* dev, int nvec, int type)
    * We expect only arch-specific PCI host bus controller driver
    * or quirks for specific PCI bridges to be setting NO_MSI.
    */
    - for (bus = dev->bus; bus; bus = bus->parent)
    - if (bus->bus_flags & PCI_BUS_FLAGS_NO_MSI)
    + for (bus = dev->bus; bus; bus = bus->parent) {
    + if (bus->bus_flags & PCI_BUS_FLAGS_NO_MSI) {
    + dev_printk(KERN_DEBUG, &dev->dev,
    + "MSI: bus check failed\n");
    return -EINVAL;
    + }
    + }

    ret = arch_msi_check_device(dev, nvec, type);
    - if (ret)
    + if (ret) {
    + dev_printk(KERN_DEBUG, &dev->dev, "MSI: arch check failed\n");
    return ret;
    + }

    - if (!pci_find_capability(dev, type))
    + if (!pci_find_capability(dev, type)) {
    + dev_printk(KERN_DEBUG, &dev->dev, "MSI: no capability found\n");
    return -EINVAL;
    + }

    return 0;
    }
    @@ -669,26 +686,37 @@ int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int nvec)
    int i, j;
    u16 control;

    - if (!entries)
    - return -EINVAL;
    -
    status = pci_msi_check_device(dev, nvec, PCI_CAP_ID_MSIX);
    if (status)
    return status;

    + if (!entries) {
    + dev_printk(KERN_DEBUG, &dev->dev, "MSI: null entries\n");
    + return -EINVAL;
    + }
    +
    pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
    pci_read_config_word(dev, msi_control_reg(pos), &control);
    nr_entries = multi_msix_capable(control);
    - if (nvec > nr_entries)
    + if (nvec > nr_entries) {
    + dev_printk(KERN_DEBUG, &dev->dev, "MSI: too many entries\n");
    return -EINVAL;
    + }

    /* Check for any invalid entries */
    for (i = 0; i < nvec; i++) {
    - if (entries[i].entry >= nr_entries)
    + if (entries[i].entry >= nr_entries) {
    + dev_printk(KERN_DEBUG, &dev->dev,
    + "MSI: invalid entry %d\n", i);
    return -EINVAL; /* invalid entry */
    + }
    for (j = i + 1; j < nvec; j++) {
    - if (entries[i].entry == entries[j].entry)
    + if (entries[i].entry == entries[j].entry) {
    + dev_printk(KERN_DEBUG, &dev->dev,
    + "MSI: duplicate entries %d, %d\n",
    + i, j);
    return -EINVAL; /* duplicate entry */
    + }
    }
    }
    WARN_ON(!!dev->msix_enabled);
    --
    1.5.3.7.1.g4e596e




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