radeon: Test for PCI root bus before assuming bus->self

If we assign a Radeon device to a virtual machine, we can no longer
assume a fixed hardware topology, like the GPU having a parent device.
This patch simply adds a few pci_is_root_bus() tests to avoid passing
a NULL pointer to PCI access functions, allowing the radeon driver to
work in a QEMU 440FX machine with an assigned HD8570 on the emulated
PCI root bus.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

2 files changed, 10 insertions, 2 deletions

diff --git a/drivers/gpu/drm/radeon/cik.c b/drivers/gpu/drm/radeon/cik.c
index e57698847be5..fa9565957f9d 100644
--- a/drivers/gpu/drm/radeon/cik.c
+++ b/drivers/gpu/drm/radeon/cik.c
@@ -9563,6 +9563,9 @@ static void cik_pcie_gen3_enable(struct radeon_device *rdev)
         int ret, i;
         u16 tmp16;
 
+        if (pci_is_root_bus(rdev->pdev->bus))
+                return;
+
         if (radeon_pcie_gen2 == 0)
                 return;
 
@@ -9789,7 +9792,8 @@ static void cik_program_aspm(struct radeon_device *rdev)
                         if (orig != data)
                                 WREG32_PCIE_PORT(PCIE_LC_LINK_WIDTH_CNTL, data);
 
-                        if (!disable_clkreq) {
+                        if (!disable_clkreq &&
+                            !pci_is_root_bus(rdev->pdev->bus)) {
                                 struct pci_dev *root = rdev->pdev->bus->self;
                                 u32 lnkcap;
 
diff --git a/drivers/gpu/drm/radeon/si.c b/drivers/gpu/drm/radeon/si.c
index 739e0a5349f8..6bce40847753 100644
--- a/drivers/gpu/drm/radeon/si.c
+++ b/drivers/gpu/drm/radeon/si.c
@@ -7188,6 +7188,9 @@ static void si_pcie_gen3_enable(struct radeon_device *rdev)
         int ret, i;
         u16 tmp16;
 
+        if (pci_is_root_bus(rdev->pdev->bus))
+                return;
+
         if (radeon_pcie_gen2 == 0)
                 return;
 
@@ -7465,7 +7468,8 @@ static void si_program_aspm(struct radeon_device *rdev)
                         if (orig != data)
                                 WREG32_PIF_PHY1(PB1_PIF_CNTL, data);
 
-                        if (!disable_clkreq) {
+                        if (!disable_clkreq &&
+                            !pci_is_root_bus(rdev->pdev->bus)) {
                                 struct pci_dev *root = rdev->pdev->bus->self;
                                 u32 lnkcap;