drm/i915: Support PCH no display

GEN supports a fusing option which subtracts the PCH display (making the
CPU display also useless). In this configuration MMIO which gets decoded
to a certain range will hang the CPU.

For us, this is sort of the equivalent of having no pipes, and we can
easily modify some code to not do certain things with no pipes.

v2: Moved the num pipes check up in the call chain, and removed extra
checks noted by Daniel. For more details, see:
http://lists.freedesktop.org/archives/intel-gfx/2013-March/025746.html

v3: Drop the intel_setup_overlay check (Daniel)
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_dma.c

@@ -1322,6 +1322,10 @@ static int i915_load_modeset_init(struct drm_device *dev)
 	/* Always safe in the mode setting case. */
 	/* FIXME: do pre/post-mode set stuff in core KMS code */
 	dev->vblank_disable_allowed = 1;
+	if (INTEL_INFO(dev)->num_pipes == 0) {
+		dev_priv->mm.suspended = 0;
+		return 0;
+	}
 
 	ret = intel_fbdev_init(dev);
 	if (ret)
@@ -1634,9 +1638,11 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	if (IS_VALLEYVIEW(dev))
 		dev_priv->num_plane = 2;
 
+	if (INTEL_INFO(dev)->num_pipes) {
 		ret = drm_vblank_init(dev, INTEL_INFO(dev)->num_pipes);
 		if (ret)
 			goto out_gem_unload;
+	}
 
 	/* Start out suspended */
 	dev_priv->mm.suspended = 1;
@@ -1651,9 +1657,11 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 
 	i915_setup_sysfs(dev);
 
+	if (INTEL_INFO(dev)->num_pipes) {
 		/* Must be done after probing outputs */
 		intel_opregion_init(dev);
 		acpi_video_register();
+	}
 
 	if (IS_GEN5(dev))
 		intel_gpu_ips_init(dev_priv);

drivers/gpu/drm/i915/intel_display.c

@@ -8991,6 +8991,9 @@ void intel_modeset_init(struct drm_device *dev)
 
 	intel_init_pm(dev);
 
+	if (INTEL_INFO(dev)->num_pipes == 0)
+		return;
+
 	intel_init_display(dev);
 
 	if (IS_GEN2(dev)) {

drivers/gpu/drm/i915/intel_fb.c

@@ -283,6 +283,9 @@ void intel_fb_restore_mode(struct drm_device *dev)
 	struct drm_mode_config *config = &dev->mode_config;
 	struct drm_plane *plane;
 
+	if (INTEL_INFO(dev)->num_pipes == 0)
+		return;
+
 	drm_modeset_lock_all(dev);
 
 	ret = drm_fb_helper_restore_fbdev_mode(&dev_priv->fbdev->helper);