drm/radeon: Don't register Thunderbolt eGPU with vga_switcheroo

An external Thunderbolt GPU can neither drive the laptop's panel nor be
powered off by the platform, so there's no point in registering it with
vga_switcheroo.  In fact, when the external GPU is runtime suspended,
vga_switcheroo will cut power to the internal discrete GPU, resulting in
a lockup.  Moreover AMD's Windows driver special-cases Thunderbolt as
well.
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: http://patchwork.freedesktop.org/patch/msgid/72d8a9645aece3eff44e116303f0fec8be061c88.1489145162.git.lukas@wunner.de

drivers/gpu/drm/radeon/radeon_device.c

@@ -1471,7 +1471,9 @@ int radeon_device_init(struct radeon_device *rdev,
 
 	if (rdev->flags & RADEON_IS_PX)
 		runtime = true;
-	vga_switcheroo_register_client(rdev->pdev, &radeon_switcheroo_ops, runtime);
+	if (!pci_is_thunderbolt_attached(rdev->pdev))
+		vga_switcheroo_register_client(rdev->pdev,
+					       &radeon_switcheroo_ops, runtime);
 	if (runtime)
 		vga_switcheroo_init_domain_pm_ops(rdev->dev, &rdev->vga_pm_domain);
 
@@ -1564,7 +1566,8 @@ void radeon_device_fini(struct radeon_device *rdev)
 	/* evict vram memory */
 	radeon_bo_evict_vram(rdev);
 	radeon_fini(rdev);
-	vga_switcheroo_unregister_client(rdev->pdev);
+	if (!pci_is_thunderbolt_attached(rdev->pdev))
+		vga_switcheroo_unregister_client(rdev->pdev);
 	if (rdev->flags & RADEON_IS_PX)
 		vga_switcheroo_fini_domain_pm_ops(rdev->dev);
 	vga_client_register(rdev->pdev, NULL, NULL, NULL);

drivers/gpu/drm/radeon/radeon_kms.c

@@ -115,7 +115,8 @@ int radeon_driver_load_kms(struct drm_device *dev, unsigned long flags)
 
 	if ((radeon_runtime_pm != 0) &&
 	    radeon_has_atpx() &&
-	    ((flags & RADEON_IS_IGP) == 0))
+	    ((flags & RADEON_IS_IGP) == 0) &&
+	    !pci_is_thunderbolt_attached(rdev->pdev))
 		flags |= RADEON_IS_PX;
 
 	/* radeon_device_init should report only fatal error