iommu/amd: Cache pdev pointer to root-bridge

commit c1bf94ec upstream.

At some point pci_get_bus_and_slot started to enable
interrupts. Since this function is used in the
amd_iommu_resume path it will enable interrupts on resume
which causes a warning. The fix will use a cached pointer
to the root-bridge to re-enable the IOMMU in case the BIOS
is broken.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/iommu/amd_iommu_init.c

@@ -943,6 +943,9 @@ static int __init init_iommu_one(struct amd_iommu *iommu, struct ivhd_header *h)
 	if (!iommu->dev)
 		return 1;
 
+	iommu->root_pdev = pci_get_bus_and_slot(iommu->dev->bus->number,
+						PCI_DEVFN(0, 0));
+
 	iommu->cap_ptr = h->cap_ptr;
 	iommu->pci_seg = h->pci_seg;
 	iommu->mmio_phys = h->mmio_phys;
@@ -1225,20 +1228,16 @@ static void iommu_apply_resume_quirks(struct amd_iommu *iommu)
 {
 	int i, j;
 	u32 ioc_feature_control;
-	struct pci_dev *pdev = NULL;
+	struct pci_dev *pdev = iommu->root_pdev;
 
 	/* RD890 BIOSes may not have completely reconfigured the iommu */
-	if (!is_rd890_iommu(iommu->dev))
+	if (!is_rd890_iommu(iommu->dev) || !pdev)
 		return;
 
 	/*
 	 * First, we need to ensure that the iommu is enabled. This is
 	 * controlled by a register in the northbridge
 	 */
-	pdev = pci_get_bus_and_slot(iommu->dev->bus->number, PCI_DEVFN(0, 0));
-
-	if (!pdev)
-		return;
 
 	/* Select Northbridge indirect register 0x75 and enable writing */
 	pci_write_config_dword(pdev, 0x60, 0x75 | (1 << 7));
@@ -1248,8 +1247,6 @@ static void iommu_apply_resume_quirks(struct amd_iommu *iommu)
 	if (!(ioc_feature_control & 0x1))
 		pci_write_config_dword(pdev, 0x64, ioc_feature_control | 1);
 
-	pci_dev_put(pdev);
-
 	/* Restore the iommu BAR */
 	pci_write_config_dword(iommu->dev, iommu->cap_ptr + 4,
 			       iommu->stored_addr_lo);

drivers/iommu/amd_iommu_types.h

@@ -385,6 +385,9 @@ struct amd_iommu {
 	/* Pointer to PCI device of this IOMMU */
 	struct pci_dev *dev;
 
+	/* Cache pdev to root device for resume quirks */
+	struct pci_dev *root_pdev;
+
 	/* physical address of MMIO space */
 	u64 mmio_phys;
 	/* virtual address of MMIO space */