drm/i915/dg2: Add fake PCH

As with DG1, DG2 has an ICL-style south display interface provided on
the same PCI device.  Add a fake PCH to ensure DG2 takes the appropriate
codepaths for south display handling.

Bspec: 54871, 50062, 49961, 53673
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Aditya Swarup <aditya.swarup@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210721223043.834562-11-matthew.d.roper@intel.com

drivers/gpu/drm/i915/i915_irq.c

@@ -207,7 +207,7 @@ static void intel_hpd_init_pins(struct drm_i915_private *dev_priv)
 	    (!HAS_PCH_SPLIT(dev_priv) || HAS_PCH_NOP(dev_priv)))
 		return;
 
-	if (HAS_PCH_DG1(dev_priv))
+	if (INTEL_PCH_TYPE(dev_priv) >= PCH_DG1)
 		hpd->pch_hpd = hpd_sde_dg1;
 	else if (INTEL_PCH_TYPE(dev_priv) >= PCH_ICP)
 		hpd->pch_hpd = hpd_icp;

drivers/gpu/drm/i915/intel_pch.c

@@ -211,6 +211,9 @@ void intel_detect_pch(struct drm_i915_private *dev_priv)
 	if (IS_DG1(dev_priv)) {
 		dev_priv->pch_type = PCH_DG1;
 		return;
+	} else if (IS_DG2(dev_priv)) {
+		dev_priv->pch_type = PCH_DG2;
+		return;
 	}
 
 	/*

drivers/gpu/drm/i915/intel_pch.h

@@ -30,6 +30,7 @@ enum intel_pch {
 
 	/* Fake PCHs, functionality handled on the same PCI dev */
 	PCH_DG1 = 1024,
+	PCH_DG2,
 };
 
 #define INTEL_PCH_DEVICE_ID_MASK		0xff80
@@ -62,6 +63,7 @@ enum intel_pch {
 
 #define INTEL_PCH_TYPE(dev_priv)		((dev_priv)->pch_type)
 #define INTEL_PCH_ID(dev_priv)			((dev_priv)->pch_id)
+#define HAS_PCH_DG2(dev_priv)			(INTEL_PCH_TYPE(dev_priv) == PCH_DG2)
 #define HAS_PCH_ADP(dev_priv)			(INTEL_PCH_TYPE(dev_priv) == PCH_ADP)
 #define HAS_PCH_DG1(dev_priv)			(INTEL_PCH_TYPE(dev_priv) == PCH_DG1)
 #define HAS_PCH_JSP(dev_priv)			(INTEL_PCH_TYPE(dev_priv) == PCH_JSP)