[bug report] drm/amdgpu: cache gpu pcie link width

[Dan Carpenter]

Hello Alex Deucher,

Commit 8fae3b201fee ("drm/amdgpu: cache gpu pcie link width") from
Jan 6, 2025 (linux-next), leads to the following Smatch static
checker warning:

	drivers/gpu/drm/amd/amdgpu/amdgpu_device.c:6193 amdgpu_device_gpu_bandwidth()
	error: we previously assumed 'parent' could be null (see line 6180)

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
    6170 static void amdgpu_device_gpu_bandwidth(struct amdgpu_device *adev,
    6171                                         enum pci_bus_speed *speed,
    6172                                         enum pcie_link_width *width)
    6173 {
    6174         struct pci_dev *parent = adev->pdev;
    6175 
    6176         if (!speed || !width)
    6177                 return;
    6178 
    6179         parent = pci_upstream_bridge(parent);
    6180         if (parent && parent->vendor == PCI_VENDOR_ID_ATI) {
                     ^^^^^^
If parent is NULL

    6181                 /* use the upstream/downstream switches internal to dGPU */
    6182                 *speed = pcie_get_speed_cap(parent);
    6183                 *width = pcie_get_width_cap(parent);
    6184                 while ((parent = pci_upstream_bridge(parent))) {
    6185                         if (parent->vendor == PCI_VENDOR_ID_ATI) {
    6186                                 /* use the upstream/downstream switches internal to dGPU */
    6187                                 *speed = pcie_get_speed_cap(parent);
    6188                                 *width = pcie_get_width_cap(parent);
    6189                         }
    6190                 }
    6191         } else {
    6192                 /* use the device itself */
--> 6193                 *speed = pcie_get_speed_cap(parent);
                                                     ^^^^^^
Then we are toasted here.

    6194                 *width = pcie_get_width_cap(parent);
    6195         }
    6196 }

regards,
dan carpenter