static void intel_increase_pllclock(struct drm_crtc *crtc);
 static void intel_crtc_update_cursor(struct drm_crtc *crtc, bool on);
 
+static void i9xx_crtc_clock_get(struct intel_crtc *crtc,
+                               struct intel_crtc_config *pipe_config);
+static void ironlake_crtc_clock_get(struct intel_crtc *crtc,
+                                   struct intel_crtc_config *pipe_config);
+
 typedef struct {
        int     min, max;
 } intel_range_t;
 }
 
 /* Returns the clock of the currently programmed mode of the given pipe. */
-static int intel_crtc_clock_get(struct drm_device *dev, struct drm_crtc *crtc)
+static void i9xx_crtc_clock_get(struct intel_crtc *crtc,
+                               struct intel_crtc_config *pipe_config)
 {
+       struct drm_device *dev = crtc->base.dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
-       struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-       int pipe = intel_crtc->pipe;
+       int pipe = pipe_config->cpu_transcoder;
        u32 dpll = I915_READ(DPLL(pipe));
        u32 fp;
        intel_clock_t clock;
                default:
                        DRM_DEBUG_KMS("Unknown DPLL mode %08x in programmed "
                                  "mode\n", (int)(dpll & DPLL_MODE_MASK));
-                       return 0;
+                       pipe_config->adjusted_mode.clock = 0;
+                       return;
                }
 
                if (IS_PINEVIEW(dev))
                }
        }
 
-       /* XXX: It would be nice to validate the clocks, but we can't reuse
-        * i830PllIsValid() because it relies on the xf86_config connector
-        * configuration being accurate, which it isn't necessarily.
+       pipe_config->adjusted_mode.clock = clock.dot *
+               pipe_config->pixel_multiplier;
+}
+
+static void ironlake_crtc_clock_get(struct intel_crtc *crtc,
+                                   struct intel_crtc_config *pipe_config)
+{
+       struct drm_device *dev = crtc->base.dev;
+       struct drm_i915_private *dev_priv = dev->dev_private;
+       enum transcoder cpu_transcoder = pipe_config->cpu_transcoder;
+       int link_freq, repeat;
+       u64 clock;
+       u32 link_m, link_n;
+
+       repeat = pipe_config->pixel_multiplier;
+
+       /*
+        * The calculation for the data clock is:
+        * pixel_clock = ((m/n)*(link_clock * nr_lanes * repeat))/bpp
+        * But we want to avoid losing precison if possible, so:
+        * pixel_clock = ((m * link_clock * nr_lanes * repeat)/(n*bpp))
+        *
+        * and the link clock is simpler:
+        * link_clock = (m * link_clock * repeat) / n
+        */
+
+       /*
+        * We need to get the FDI or DP link clock here to derive
+        * the M/N dividers.
+        *
+        * For FDI, we read it from the BIOS or use a fixed 2.7GHz.
+        * For DP, it's either 1.62GHz or 2.7GHz.
+        * We do our calculations in 10*MHz since we don't need much precison.
         */
+       if (pipe_config->has_pch_encoder)
+               link_freq = intel_fdi_link_freq(dev) * 10000;
+       else
+               link_freq = pipe_config->port_clock;
+
+       link_m = I915_READ(PIPE_LINK_M1(cpu_transcoder));
+       link_n = I915_READ(PIPE_LINK_N1(cpu_transcoder));
+
+       if (!link_m || !link_n)
+               return;
 
-       return clock.dot;
+       clock = ((u64)link_m * (u64)link_freq * (u64)repeat);
+       do_div(clock, link_n);
+
+       pipe_config->adjusted_mode.clock = clock;
 }
 
 /** Returns the currently programmed mode of the given pipe. */
        struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
        enum transcoder cpu_transcoder = intel_crtc->config.cpu_transcoder;
        struct drm_display_mode *mode;
+       struct intel_crtc_config pipe_config;
        int htot = I915_READ(HTOTAL(cpu_transcoder));
        int hsync = I915_READ(HSYNC(cpu_transcoder));
        int vtot = I915_READ(VTOTAL(cpu_transcoder));
        if (!mode)
                return NULL;
 
-       mode->clock = intel_crtc_clock_get(dev, crtc);
+       /*
+        * Construct a pipe_config sufficient for getting the clock info
+        * back out of crtc_clock_get.
+        *
+        * Note, if LVDS ever uses a non-1 pixel multiplier, we'll need
+        * to use a real value here instead.
+        */
+       pipe_config.cpu_transcoder = intel_crtc->pipe;
+       pipe_config.pixel_multiplier = 1;
+       i9xx_crtc_clock_get(intel_crtc, &pipe_config);
+
+       mode->clock = pipe_config.adjusted_mode.clock;
        mode->hdisplay = (htot & 0xffff) + 1;
        mode->htotal = ((htot & 0xffff0000) >> 16) + 1;
        mode->hsync_start = (hsync & 0xffff) + 1;
 
 }
 
+static bool intel_fuzzy_clock_check(struct intel_crtc_config *cur,
+                                   struct intel_crtc_config *new)
+{
+       int clock1, clock2, diff;
+
+       clock1 = cur->adjusted_mode.clock;
+       clock2 = new->adjusted_mode.clock;
+
+       if (clock1 == clock2)
+               return true;
+
+       if (!clock1 || !clock2)
+               return false;
+
+       diff = abs(clock1 - clock2);
+
+       if (((((diff + clock1 + clock2) * 100)) / (clock1 + clock2)) < 105)
+               return true;
+
+       return false;
+}
+
 #define for_each_intel_crtc_masked(dev, mask, intel_crtc) \
        list_for_each_entry((intel_crtc), \
                            &(dev)->mode_config.crtc_list, \
 #undef PIPE_CONF_CHECK_FLAGS
 #undef PIPE_CONF_QUIRK
 
+       if (!IS_HASWELL(dev)) {
+               if (!intel_fuzzy_clock_check(current_config, pipe_config)) {
+                       DRM_ERROR("mismatch in clock (expected %d, found %d\n",
+                                 current_config->adjusted_mode.clock,
+                                 pipe_config->adjusted_mode.clock);
+                       return false;
+               }
+       }
+
        return true;
 }
 
                                    base.head) {
                        if (encoder->base.crtc != &crtc->base)
                                continue;
-                       if (encoder->get_config)
+                       if (encoder->get_config &&
+                           dev_priv->display.get_clock) {
                                encoder->get_config(encoder, &pipe_config);
+                               dev_priv->display.get_clock(crtc,
+                                                           &pipe_config);
+                       }
                }
 
                WARN(crtc->active != active,
                dev_priv->display.update_plane = ironlake_update_plane;
        } else if (HAS_PCH_SPLIT(dev)) {
                dev_priv->display.get_pipe_config = ironlake_get_pipe_config;
+               dev_priv->display.get_clock = ironlake_crtc_clock_get;
                dev_priv->display.crtc_mode_set = ironlake_crtc_mode_set;
                dev_priv->display.crtc_enable = ironlake_crtc_enable;
                dev_priv->display.crtc_disable = ironlake_crtc_disable;
                dev_priv->display.update_plane = ironlake_update_plane;
        } else if (IS_VALLEYVIEW(dev)) {
                dev_priv->display.get_pipe_config = i9xx_get_pipe_config;
+               dev_priv->display.get_clock = i9xx_crtc_clock_get;
                dev_priv->display.crtc_mode_set = i9xx_crtc_mode_set;
                dev_priv->display.crtc_enable = valleyview_crtc_enable;
                dev_priv->display.crtc_disable = i9xx_crtc_disable;
                dev_priv->display.update_plane = i9xx_update_plane;
        } else {
                dev_priv->display.get_pipe_config = i9xx_get_pipe_config;
+               dev_priv->display.get_clock = i9xx_crtc_clock_get;
                dev_priv->display.crtc_mode_set = i9xx_crtc_mode_set;
                dev_priv->display.crtc_enable = i9xx_crtc_enable;
                dev_priv->display.crtc_disable = i9xx_crtc_disable;
                if (encoder->get_hw_state(encoder, &pipe)) {
                        crtc = to_intel_crtc(dev_priv->pipe_to_crtc_mapping[pipe]);
                        encoder->base.crtc = &crtc->base;
-                       if (encoder->get_config)
+                       if (encoder->get_config &&
+                           dev_priv->display.get_clock) {
                                encoder->get_config(encoder, &crtc->config);
+                               dev_priv->display.get_clock(crtc,
+                                                           &crtc->config);
+                       }
                } else {
                        encoder->base.crtc = NULL;
                }