drm/i915: more virtual south bridge detection

Commit "30c964a6 drm/i915: Detect virtual south bridge" detects and
handles the southbridge emulated by vmware esx.  Add the ich9 south
bridge emulated by 'qemu -M q35'.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -565,7 +565,8 @@ void intel_detect_pch(struct drm_device *dev)
 				DRM_DEBUG_KMS("Found SunrisePoint LP PCH\n");
 				WARN_ON(!IS_SKYLAKE(dev) &&
 					!IS_KABYLAKE(dev));
-			} else if (id == INTEL_PCH_P2X_DEVICE_ID_TYPE) {
+			} else if ((id == INTEL_PCH_P2X_DEVICE_ID_TYPE) ||
+				   (id == INTEL_PCH_QEMU_DEVICE_ID_TYPE)) {
 				dev_priv->pch_type = intel_virt_detect_pch(dev);
 			} else
 				continue;

drivers/gpu/drm/i915/i915_drv.h

@@ -2609,6 +2609,7 @@ struct drm_i915_cmd_table {
 #define INTEL_PCH_SPT_DEVICE_ID_TYPE		0xA100
 #define INTEL_PCH_SPT_LP_DEVICE_ID_TYPE		0x9D00
 #define INTEL_PCH_P2X_DEVICE_ID_TYPE		0x7100
+#define INTEL_PCH_QEMU_DEVICE_ID_TYPE		0x2900 /* qemu q35 has 2918 */
 
 #define INTEL_PCH_TYPE(dev) (__I915__(dev)->pch_type)
 #define HAS_PCH_SPT(dev) (INTEL_PCH_TYPE(dev) == PCH_SPT)