drm/i915: Try to guess PCH type even without ISA bridge

Some vmm like hyperv and crosvm don't supply any ISA bridge to their guest,
when igd passthrough is equipped on these vmm, guest i915 display may
couldn't work as guest i915 detects PCH_NONE pch type.

When i915 runs as guest, this patch guess pch type through gpu type even
without ISA bridge.

v2: Fix CI warning
v3: Add HAS_DISPLAY()= true condition beforce guessing virt pch, then
    refactori.
v4: Fix CI warning
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Co-developed-by: Xiong Zhang <xiong.y.zhang@intel.com>
Signed-off-by: Xiong Zhang <xiong.y.zhang@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210114005819.4290-1-xiong.y.zhang@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -1754,6 +1754,11 @@ tgl_revids_get(struct drm_i915_private *dev_priv)
 #define INTEL_DISPLAY_ENABLED(dev_priv) \
 	(drm_WARN_ON(&(dev_priv)->drm, !HAS_DISPLAY(dev_priv)), !(dev_priv)->params.disable_display)
 
+static inline bool run_as_guest(void)
+{
+	return !hypervisor_is_type(X86_HYPER_NATIVE);
+}
+
 static inline bool intel_vtd_active(void)
 {
 #ifdef CONFIG_INTEL_IOMMU
@@ -1762,7 +1767,7 @@ static inline bool intel_vtd_active(void)
 #endif
 
 	/* Running as a guest, we assume the host is enforcing VT'd */
-	return !hypervisor_is_type(X86_HYPER_NATIVE);
+	return run_as_guest();
 }
 
 static inline bool intel_scanout_needs_vtd_wa(struct drm_i915_private *dev_priv)

drivers/gpu/drm/i915/intel_pch.c

@@ -143,8 +143,9 @@ static bool intel_is_virt_pch(unsigned short id,
 		 sdevice == PCI_SUBDEVICE_ID_QEMU));
 }
 
-static unsigned short
-intel_virt_detect_pch(const struct drm_i915_private *dev_priv)
+static void
+intel_virt_detect_pch(const struct drm_i915_private *dev_priv,
+		      unsigned short *pch_id, enum intel_pch *pch_type)
 {
 	unsigned short id = 0;
 
@@ -181,12 +182,21 @@ intel_virt_detect_pch(const struct drm_i915_private *dev_priv)
 	else
 		drm_dbg_kms(&dev_priv->drm, "Assuming no PCH\n");
 
-	return id;
+	*pch_type = intel_pch_type(dev_priv, id);
+
+	/* Sanity check virtual PCH id */
+	if (drm_WARN_ON(&dev_priv->drm,
+			id && *pch_type == PCH_NONE))
+		id = 0;
+
+	*pch_id = id;
 }
 
 void intel_detect_pch(struct drm_i915_private *dev_priv)
 {
 	struct pci_dev *pch = NULL;
+	unsigned short id;
+	enum intel_pch pch_type;
 
 	/* DG1 has south engine display on the same PCI device */
 	if (IS_DG1(dev_priv)) {
@@ -206,9 +216,6 @@ void intel_detect_pch(struct drm_i915_private *dev_priv)
 	 * of only checking the first one.
 	 */
 	while ((pch = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, pch))) {
-		unsigned short id;
-		enum intel_pch pch_type;
-
 		if (pch->vendor != PCI_VENDOR_ID_INTEL)
 			continue;
 
@@ -221,14 +228,7 @@ void intel_detect_pch(struct drm_i915_private *dev_priv)
 			break;
 		} else if (intel_is_virt_pch(id, pch->subsystem_vendor,
 					     pch->subsystem_device)) {
-			id = intel_virt_detect_pch(dev_priv);
-			pch_type = intel_pch_type(dev_priv, id);
-
-			/* Sanity check virtual PCH id */
-			if (drm_WARN_ON(&dev_priv->drm,
-					id && pch_type == PCH_NONE))
-				id = 0;
-
+			intel_virt_detect_pch(dev_priv, &id, &pch_type);
 			dev_priv->pch_type = pch_type;
 			dev_priv->pch_id = id;
 			break;
@@ -244,10 +244,15 @@ void intel_detect_pch(struct drm_i915_private *dev_priv)
 			    "Display disabled, reverting to NOP PCH\n");
 		dev_priv->pch_type = PCH_NOP;
 		dev_priv->pch_id = 0;
+	} else if (!pch) {
+		if (run_as_guest() && HAS_DISPLAY(dev_priv)) {
+			intel_virt_detect_pch(dev_priv, &id, &pch_type);
+			dev_priv->pch_type = pch_type;
+			dev_priv->pch_id = id;
+		} else {
+			drm_dbg_kms(&dev_priv->drm, "No PCH found.\n");
+		}
 	}
 
-	if (!pch)
-		drm_dbg_kms(&dev_priv->drm, "No PCH found.\n");
-
 	pci_dev_put(pch);
 }