diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 83446b55f731f1f87f85b89252732ca38f9998dc..a95c69392afc56560158a57d12e7c9eca4395235 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2709,27 +2709,19 @@ fdi_reduce_ratio(u32 *num, u32 *den)
 	}
 }
 
-#define DATA_N 0x800000
-#define LINK_N 0x80000
-
 static void
 ironlake_compute_m_n(int bits_per_pixel, int nlanes, int pixel_clock,
 		     int link_clock, struct fdi_m_n *m_n)
 {
-	u64 temp;
-
 	m_n->tu = 64; /* default size */
 
-	temp = (u64) DATA_N * pixel_clock;
-	temp = div_u64(temp, link_clock);
-	m_n->gmch_m = div_u64(temp * bits_per_pixel, nlanes);
-	m_n->gmch_m >>= 3; /* convert to bytes_per_pixel */
-	m_n->gmch_n = DATA_N;
+	/* BUG_ON(pixel_clock > INT_MAX / 36); */
+	m_n->gmch_m = bits_per_pixel * pixel_clock;
+	m_n->gmch_n = link_clock * nlanes * 8;
 	fdi_reduce_ratio(&m_n->gmch_m, &m_n->gmch_n);
 
-	temp = (u64) LINK_N * pixel_clock;
-	m_n->link_m = div_u64(temp, link_clock);
-	m_n->link_n = LINK_N;
+	m_n->link_m = pixel_clock;
+	m_n->link_n = link_clock;
 	fdi_reduce_ratio(&m_n->link_m, &m_n->link_n);
 }
 
@@ -3713,6 +3705,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 
 	/* FDI link */
 	if (HAS_PCH_SPLIT(dev)) {
+		int pixel_multiplier = intel_mode_get_pixel_multiplier(adjusted_mode);
 		int lane = 0, link_bw, bpp;
 		/* CPU eDP doesn't require FDI link, so just set DP M/N
 		   according to current link config */
@@ -3796,6 +3789,8 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 
 		intel_crtc->fdi_lanes = lane;
 
+		if (pixel_multiplier > 1)
+			link_bw *= pixel_multiplier;
 		ironlake_compute_m_n(bpp, lane, target_clock, link_bw, &m_n);
 	}
 
@@ -5263,6 +5258,55 @@ static const struct drm_crtc_funcs intel_crtc_funcs = {
 	.page_flip = intel_crtc_page_flip,
 };
 
+static void intel_sanitize_modesetting(struct drm_device *dev,
+				       int pipe, int plane)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 reg, val;
+
+	if (HAS_PCH_SPLIT(dev))
+		return;
+
+	/* Who knows what state these registers were left in by the BIOS or
+	 * grub?
+	 *
+	 * If we leave the registers in a conflicting state (e.g. with the
+	 * display plane reading from the other pipe than the one we intend
+	 * to use) then when we attempt to teardown the active mode, we will
+	 * not disable the pipes and planes in the correct order -- leaving
+	 * a plane reading from a disabled pipe and possibly leading to
+	 * undefined behaviour.
+	 */
+
+	reg = DSPCNTR(plane);
+	val = I915_READ(reg);
+
+	if ((val & DISPLAY_PLANE_ENABLE) == 0)
+		return;
+	if (!!(val & DISPPLANE_SEL_PIPE_MASK) == pipe)
+		return;
+
+	/* This display plane is active and attached to the other CPU pipe. */
+	pipe = !pipe;
+
+	/* Disable the plane and wait for it to stop reading from the pipe. */
+	I915_WRITE(reg, val & ~DISPLAY_PLANE_ENABLE);
+	intel_flush_display_plane(dev, plane);
+
+	if (IS_GEN2(dev))
+		intel_wait_for_vblank(dev, pipe);
+
+	if (pipe == 0 && (dev_priv->quirks & QUIRK_PIPEA_FORCE))
+		return;
+
+	/* Switch off the pipe. */
+	reg = PIPECONF(pipe);
+	val = I915_READ(reg);
+	if (val & PIPECONF_ENABLE) {
+		I915_WRITE(reg, val & ~PIPECONF_ENABLE);
+		intel_wait_for_pipe_off(dev, pipe);
+	}
+}
 
 static void intel_crtc_init(struct drm_device *dev, int pipe)
 {
@@ -5314,6 +5358,8 @@ static void intel_crtc_init(struct drm_device *dev, int pipe)
 
 	setup_timer(&intel_crtc->idle_timer, intel_crtc_idle_timer,
 		    (unsigned long)intel_crtc);
+
+	intel_sanitize_modesetting(dev, intel_crtc->pipe, intel_crtc->plane);
 }
 
 int intel_get_pipe_from_crtc_id(struct drm_device *dev, void *data,