drm/i915: Align initial plane backing objects correctly

Some bios really like to joke and start the planes at an offset ...
hooray!

Align start and end to fix this.

v2: Fixup calculation of size, spotted by Chris Wilson.

v3: Fix serious fumble I've just spotted.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=86883
Cc: stable@vger.kernel.org
Cc: Johannes W <jargon@molb.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Reported-and-tested-by: Johannes W <jargon@molb.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
[Jani: split WARN_ONs, rebase on v4.0-rc1]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_gem_stolen.c

@@ -485,10 +485,8 @@ i915_gem_object_create_stolen_for_preallocated(struct drm_device *dev,
 			stolen_offset, gtt_offset, size);
 
 	/* KISS and expect everything to be page-aligned */
-	BUG_ON(stolen_offset & 4095);
-	BUG_ON(size & 4095);
-
-	if (WARN_ON(size == 0))
+	if (WARN_ON(size == 0) || WARN_ON(size & 4095) ||
+	    WARN_ON(stolen_offset & 4095))
 		return NULL;
 
 	stolen = kzalloc(sizeof(*stolen), GFP_KERNEL);

drivers/gpu/drm/i915/intel_display.c

@@ -2371,13 +2371,19 @@ intel_alloc_plane_obj(struct intel_crtc *crtc,
 	struct drm_device *dev = crtc->base.dev;
 	struct drm_i915_gem_object *obj = NULL;
 	struct drm_mode_fb_cmd2 mode_cmd = { 0 };
-	u32 base = plane_config->base;
+	u32 base_aligned = round_down(plane_config->base, PAGE_SIZE);
+	u32 size_aligned = round_up(plane_config->base + plane_config->size,
+				    PAGE_SIZE);
+
+	size_aligned -= base_aligned;
 
 	if (plane_config->size == 0)
 		return false;
 
-	obj = i915_gem_object_create_stolen_for_preallocated(dev, base, base,
-							     plane_config->size);
+	obj = i915_gem_object_create_stolen_for_preallocated(dev,
+							     base_aligned,
+							     base_aligned,
+							     size_aligned);
 	if (!obj)
 		return false;
 
@@ -6636,7 +6642,7 @@ i9xx_get_initial_plane_config(struct intel_crtc *crtc,
 	aligned_height = intel_fb_align_height(dev, fb->height,
 					       plane_config->tiling);
 
-	plane_config->size = PAGE_ALIGN(fb->pitches[0] * aligned_height);
+	plane_config->size = fb->pitches[0] * aligned_height;
 
 	DRM_DEBUG_KMS("pipe/plane %c/%d with fb: size=%dx%d@%d, offset=%x, pitch %d, size 0x%x\n",
 		      pipe_name(pipe), plane, fb->width, fb->height,
@@ -7673,7 +7679,7 @@ skylake_get_initial_plane_config(struct intel_crtc *crtc,
 	aligned_height = intel_fb_align_height(dev, fb->height,
 					       plane_config->tiling);
 
-	plane_config->size = ALIGN(fb->pitches[0] * aligned_height, PAGE_SIZE);
+	plane_config->size = fb->pitches[0] * aligned_height;
 
 	DRM_DEBUG_KMS("pipe %c with fb: size=%dx%d@%d, offset=%x, pitch %d, size 0x%x\n",
 		      pipe_name(pipe), fb->width, fb->height,
@@ -7764,7 +7770,7 @@ ironlake_get_initial_plane_config(struct intel_crtc *crtc,
 	aligned_height = intel_fb_align_height(dev, fb->height,
 					       plane_config->tiling);
 
-	plane_config->size = PAGE_ALIGN(fb->pitches[0] * aligned_height);
+	plane_config->size = fb->pitches[0] * aligned_height;
 
 	DRM_DEBUG_KMS("pipe %c with fb: size=%dx%d@%d, offset=%x, pitch %d, size 0x%x\n",
 		      pipe_name(pipe), fb->width, fb->height,