drm/i915/bxt: Add BXT support in gen8_irq functions

This patch adds conditional checks in gen8_irq functions
to support BXT. Most of the checks just look for PCH split
availability, and block the call to PCH interrupt functions if
not available.

v2: (jani)
- drop redundant TODO comment about PCH IRQ flags on BXT
- check HAS_PCH_SPLIT instead of IS_BROXTON when handling PCH specific
  IRQ events in gen8_irq_handler()
- check HAS_PCH_SPLIT before calling the function instead of a
  corresponding early return within the called function for
  ibx_irq_reset(), ibx_irq_pre_postinstall(), ibx_irq_postinstall()
v3: (jani)
- in ironlake_irq_postinstall() and ironlake_irq_reset() HAS_PCH_SPLIT
  is always true, so drop the check for it
Reviewed-by: Satheeshakrishna M <satheeshakrishna.m@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Shashank Sharma <ppashank.sharma@intel.com> (v1)
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -2297,7 +2297,8 @@ static irqreturn_t gen8_irq_handler(int irq, void *arg)
 			DRM_ERROR("The master control interrupt lied (DE PIPE)!\n");
 	}
 
-	if (!HAS_PCH_NOP(dev) && master_ctl & GEN8_DE_PCH_IRQ) {
+	if (HAS_PCH_SPLIT(dev) && !HAS_PCH_NOP(dev) &&
+	    master_ctl & GEN8_DE_PCH_IRQ) {
 		/*
 		 * FIXME(BDW): Assume for now that the new interrupt handling
 		 * scheme also closed the SDE interrupt handling race we've seen
@@ -3133,6 +3134,7 @@ static void gen8_irq_reset(struct drm_device *dev)
 	GEN5_IRQ_RESET(GEN8_DE_MISC_);
 	GEN5_IRQ_RESET(GEN8_PCU_);
 
+	if (HAS_PCH_SPLIT(dev))
 		ibx_irq_reset(dev);
 }
 
@@ -3545,11 +3547,13 @@ static int gen8_irq_postinstall(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	if (HAS_PCH_SPLIT(dev))
 		ibx_irq_pre_postinstall(dev);
 
 	gen8_gt_irq_postinstall(dev_priv);
 	gen8_de_irq_postinstall(dev_priv);
 
+	if (HAS_PCH_SPLIT(dev))
 		ibx_irq_postinstall(dev);
 
 	I915_WRITE(GEN8_MASTER_IRQ, DE_MASTER_IRQ_CONTROL);