drm: add drm_pcie_get_max_link_width helper (v2)
Add a helper to get the max link width of the port.
Similar to the helper to get the max link speed.
v2: fix typo in commit message
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
index fcd2a86..a1fff11 100644
--- a/drivers/gpu/drm/drm_pci.c
+++ b/drivers/gpu/drm/drm_pci.c
@@ -410,6 +410,26 @@
}
EXPORT_SYMBOL(drm_pcie_get_speed_cap_mask);
+int drm_pcie_get_max_link_width(struct drm_device *dev, u32 *mlw)
+{
+ struct pci_dev *root;
+ u32 lnkcap;
+
+ *mlw = 0;
+ if (!dev->pdev)
+ return -EINVAL;
+
+ root = dev->pdev->bus->self;
+
+ pcie_capability_read_dword(root, PCI_EXP_LNKCAP, &lnkcap);
+
+ *mlw = (lnkcap & PCI_EXP_LNKCAP_MLW) >> 4;
+
+ DRM_INFO("probing mlw for device %x:%x = %x\n", root->vendor, root->device, lnkcap);
+ return 0;
+}
+EXPORT_SYMBOL(drm_pcie_get_max_link_width);
+
#else
int drm_pci_init(struct drm_driver *driver, struct pci_driver *pdriver)