drm/i915: Detect virtual south bridge

Virtualized systems often use a virtual P2X4 south bridge.
Detect this in intel_detect_pch and make a best guess as to which PCH
we should be using.

This was seen on vmware esxi hypervisor. When passing the graphics device
through to a guest, it can not pass through the PCH. Instead it simulates
a P2X4 southbridge.
Signed-off-by: Robert Beckett <robert.beckett@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -443,6 +443,34 @@ static const struct pci_device_id pciidlist[] = {		/* aka */
 
 MODULE_DEVICE_TABLE(pci, pciidlist);
 
+static enum intel_pch intel_virt_detect_pch(struct drm_device *dev)
+{
+	enum intel_pch ret = PCH_NOP;
+
+	/*
+	 * In a virtualized passthrough environment we can be in a
+	 * setup where the ISA bridge is not able to be passed through.
+	 * In this case, a south bridge can be emulated and we have to
+	 * make an educated guess as to which PCH is really there.
+	 */
+
+	if (IS_GEN5(dev)) {
+		ret = PCH_IBX;
+		DRM_DEBUG_KMS("Assuming Ibex Peak PCH\n");
+	} else if (IS_GEN6(dev) || IS_IVYBRIDGE(dev)) {
+		ret = PCH_CPT;
+		DRM_DEBUG_KMS("Assuming CouarPoint PCH\n");
+	} else if (IS_HASWELL(dev) || IS_BROADWELL(dev)) {
+		ret = PCH_LPT;
+		DRM_DEBUG_KMS("Assuming LynxPoint PCH\n");
+	} else if (IS_SKYLAKE(dev)) {
+		ret = PCH_SPT;
+		DRM_DEBUG_KMS("Assuming SunrisePoint PCH\n");
+	}
+
+	return ret;
+}
+
 void intel_detect_pch(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -503,6 +531,8 @@ void intel_detect_pch(struct drm_device *dev)
 				dev_priv->pch_type = PCH_SPT;
 				DRM_DEBUG_KMS("Found SunrisePoint LP PCH\n");
 				WARN_ON(!IS_SKYLAKE(dev));
+			} else if (id == INTEL_PCH_P2X_DEVICE_ID_TYPE) {
+				dev_priv->pch_type = intel_virt_detect_pch(dev);
 			} else
 				continue;
 

drivers/gpu/drm/i915/i915_drv.h

@@ -2608,6 +2608,7 @@ struct drm_i915_cmd_table {
 #define INTEL_PCH_LPT_LP_DEVICE_ID_TYPE		0x9c00
 #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_TYPE(dev) (__I915__(dev)->pch_type)
 #define HAS_PCH_SPT(dev) (INTEL_PCH_TYPE(dev) == PCH_SPT)