drm/i915: Store max dotclock

Store max dotclock into dev_priv structure so we are able
to filter out the modes that are not supported by our
platforms.

V2:
- limit the max dot clock frequency to max CD clock frequency
  for the gen9 and above
- limit the max dot clock frequency to 90% of the max CD clock
  frequency for the older gens
- for Cherryview the max dot clock frequency is limited to 95%
  of the max CD clock frequency
- for gen2 and gen3 the max dot clock limit is set to 90% of the
  2X max CD clock frequency

V3:
- max_dotclk variable renamed as max_dotclk_freq in i915_drv.h
- in intel_compute_max_dotclk() the rounding method changed from
  round up to round down when computing max dotclock

V4:
- Haswell and Broadwell supports now dot clocks up to max CD clock
  frequency

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 50cbc7e374cc..03e84ace8a09 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5240,6 +5240,21 @@ static void modeset_update_crtc_power_domains(struct drm_atomic_state *state)
                         modeset_put_power_domains(dev_priv, put_domains[i]);
 }
 
+static int intel_compute_max_dotclk(struct drm_i915_private *dev_priv)
+{
+        int max_cdclk_freq = dev_priv->max_cdclk_freq;
+
+        if (INTEL_INFO(dev_priv)->gen >= 9 ||
+            IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv))
+                return max_cdclk_freq;
+        else if (IS_CHERRYVIEW(dev_priv))
+                return max_cdclk_freq*95/100;
+        else if (INTEL_INFO(dev_priv)->gen < 4)
+                return 2*max_cdclk_freq*90/100;
+        else
+                return max_cdclk_freq*90/100;
+}
+
 static void intel_update_max_cdclk(struct drm_device *dev)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
@@ -5279,8 +5294,13 @@ static void intel_update_max_cdclk(struct drm_device *dev)
                 dev_priv->max_cdclk_freq = dev_priv->cdclk_freq;
         }
 
+        dev_priv->max_dotclk_freq = intel_compute_max_dotclk(dev_priv);
+
         DRM_DEBUG_DRIVER("Max CD clock rate: %d kHz\n",
                          dev_priv->max_cdclk_freq);
+
+        DRM_DEBUG_DRIVER("Max dotclock rate: %d kHz\n",
+                         dev_priv->max_dotclk_freq);
 }
 
 static void intel_update_cdclk(struct drm_device *dev)