From: Mario Limonciello mario.limonciello@amd.com
[ Upstream commit 0feda94c868d396fac3b3cb14089d2d989a07c72 ]
On many systems that have an AMD IOMMU the following sequence of warnings is observed during bootup.
``` pci 0000:00:00.2 can't derive routing for PCI INT A pci 0000:00:00.2: PCI INT A: not connected ```
This series of events happens because of the IOMMU initialization sequence order and the lack of _PRT entries for the IOMMU.
During initialization the IOMMU driver first enables the PCI device using pci_enable_device(). This will call acpi_pci_irq_enable() which will check if the interrupt is declared in a PCI routing table (_PRT) entry. According to the PCI spec [1] these routing entries are only required under PCI root bridges: The _PRT object is required under all PCI root bridges
The IOMMU is directly connected to the root complex, so there is no parent bridge to look for a _PRT entry. The first warning is emitted since no entry could be found in the hierarchy. The second warning is then emitted because the interrupt hasn't yet been configured to any value. The pin was configured in pci_read_irq() but the byte in PCI_INTERRUPT_LINE return 0xff which means "Unknown".
After that sequence of events pci_enable_msi() is called and this will allocate an interrupt.
That is both of these warnings are totally harmless because the IOMMU uses MSI for interrupts. To avoid even trying to probe for a _PRT entry mark the IOMMU as IRQ managed. This avoids both warnings.
Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/06_Device_Configuration/Device... [1] Signed-off-by: Mario Limonciello mario.limonciello@amd.com Fixes: cffe0a2b5a34 ("x86, irq: Keep balance of IOAPIC pin reference count") Reviewed-by: Vasant Hegde vasant.hegde@amd.com Link: https://lore.kernel.org/r/20240122233400.1802-1-mario.limonciello@amd.com Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/amd/init.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c index c83bd0c2a1c92..40979b0f5250f 100644 --- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c @@ -2068,6 +2068,9 @@ static int __init iommu_init_pci(struct amd_iommu *iommu) /* Prevent binding other PCI device drivers to IOMMU devices */ iommu->dev->match_driver = false;
+ /* ACPI _PRT won't have an IRQ for IOMMU */ + iommu->dev->irq_managed = 1; + pci_read_config_dword(iommu->dev, cap_ptr + MMIO_CAP_HDR_OFFSET, &iommu->cap);