drm/i915: TV pixel clock check

It is possible the we request to have a mode that has
higher pixel clock than our HW can support. This patch
checks if requested pixel clock is lower than the one
supported by the HW. The requested mode is discarded
if we cannot support the requested pixel clock.

This patch applies to TV.

V2:
- removed computation for max pixel clock

V3:
- cleanup by removing unnecessary lines

V4:
- max_pixclk variable renamed as max_dotclk
Signed-off-by: NMika Kahola <mika.kahola@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1454419003-6001-7-git-send-email-mika.kahola@intel.com

drivers/gpu/drm/i915/intel_tv.c

@@ -897,6 +897,10 @@ intel_tv_mode_valid(struct drm_connector *connector,
 {
 	struct intel_tv *intel_tv = intel_attached_tv(connector);
 	const struct tv_mode *tv_mode = intel_tv_mode_find(intel_tv);
+	int max_dotclk = to_i915(connector->dev)->max_dotclk_freq;
+
+	if (mode->clock > max_dotclk)
+		return MODE_CLOCK_HIGH;
 
 	/* Ensure TV refresh is close to desired refresh */
 	if (tv_mode && abs(tv_mode->refresh - drm_mode_vrefresh(mode) * 1000)