drm/i915: extract and improve gen8_irq_power_well_post_enable

Move it from hsw_power_well_post_enable() (intel_pm.c) to i915_irq.c
so we can reuse the nice IRQ macros we have there. The main difference
is that now we're going to check if the IIR register is non-zero when
we try to re-enable the interrupts.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -3478,6 +3478,18 @@ static void gen8_irq_reset(struct drm_device *dev)
 	ibx_irq_reset(dev);
 }
 
+void gen8_irq_power_well_post_enable(struct drm_i915_private *dev_priv)
+{
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+	GEN8_IRQ_INIT_NDX(DE_PIPE, PIPE_B, dev_priv->de_irq_mask[PIPE_B],
+			  ~dev_priv->de_irq_mask[PIPE_B]);
+	GEN8_IRQ_INIT_NDX(DE_PIPE, PIPE_C, dev_priv->de_irq_mask[PIPE_C],
+			  ~dev_priv->de_irq_mask[PIPE_C]);
+	spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
+}
+
 static void cherryview_irq_preinstall(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;

drivers/gpu/drm/i915/intel_drv.h

@@ -693,6 +693,7 @@ void intel_runtime_pm_disable_interrupts(struct drm_device *dev);
 void intel_runtime_pm_restore_interrupts(struct drm_device *dev);
 int intel_get_crtc_scanline(struct intel_crtc *crtc);
 void i9xx_check_fifo_underruns(struct drm_device *dev);
+void gen8_irq_power_well_post_enable(struct drm_i915_private *dev_priv);
 
 
 /* intel_crt.c */

drivers/gpu/drm/i915/intel_pm.c

@@ -5998,7 +5998,6 @@ bool intel_display_power_enabled(struct drm_i915_private *dev_priv,
 static void hsw_power_well_post_enable(struct drm_i915_private *dev_priv)
 {
 	struct drm_device *dev = dev_priv->dev;
-	unsigned long irqflags;
 
 	/*
 	 * After we re-enable the power well, if we touch VGA register 0x3d5
@@ -6014,21 +6013,8 @@ static void hsw_power_well_post_enable(struct drm_i915_private *dev_priv)
 	outb(inb(VGA_MSR_READ), VGA_MSR_WRITE);
 	vga_put(dev->pdev, VGA_RSRC_LEGACY_IO);
 
-	if (IS_BROADWELL(dev)) {
-		spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
-		I915_WRITE(GEN8_DE_PIPE_IMR(PIPE_B),
-			   dev_priv->de_irq_mask[PIPE_B]);
-		I915_WRITE(GEN8_DE_PIPE_IER(PIPE_B),
-			   ~dev_priv->de_irq_mask[PIPE_B] |
-			   GEN8_PIPE_VBLANK);
-		I915_WRITE(GEN8_DE_PIPE_IMR(PIPE_C),
-			   dev_priv->de_irq_mask[PIPE_C]);
-		I915_WRITE(GEN8_DE_PIPE_IER(PIPE_C),
-			   ~dev_priv->de_irq_mask[PIPE_C] |
-			   GEN8_PIPE_VBLANK);
-		POSTING_READ(GEN8_DE_PIPE_IER(PIPE_C));
-		spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
-	}
+	if (IS_BROADWELL(dev))
+		gen8_irq_power_well_post_enable(dev_priv);
 }
 
 static void hsw_set_power_well(struct drm_i915_private *dev_priv,