diff options
Diffstat (limited to 'drivers/pci')
| -rw-r--r-- | drivers/pci/msi.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index f9fdc54473c..9fc9a34ef24 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -627,22 +627,24 @@ static int msix_capability_init(struct pci_dev *dev, * pci_msi_supported - check whether MSI may be enabled on device * @dev: pointer to the pci_dev data structure of MSI device function * - * MSI must be globally enabled and supported by the device and its root - * bus. But, the root bus is not easy to find since some architectures - * have virtual busses on top of the PCI hierarchy (for instance the - * hypertransport bus), while the actual bus where MSI must be supported - * is below. So we test the MSI flag on all parent busses and assume - * that no quirk will ever set the NO_MSI flag on a non-root bus. + * Look at global flags, the device itself, and its parent busses + * to return 0 if MSI are supported for the device. **/ static int pci_msi_supported(struct pci_dev * dev) { struct pci_bus *bus; + /* MSI must be globally enabled and supported by the device */ if (!pci_msi_enable || !dev || dev->no_msi) return -EINVAL; - /* check MSI flags of all parent busses */ + /* Any bridge which does NOT route MSI transactions from it's + * secondary bus to it's primary bus must set NO_MSI flag on + * the secondary pci_bus. + * 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) return -EINVAL; |