drm/i915: set CB tuning also for the reduce clock

Since the ratio is different, we also need to pass in the parameters
for the reduced clock. Might or might not reduce flicker for the
auto-downclocking on lvds/eDP.
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -5469,7 +5469,8 @@ static void ironlake_fdi_set_m_n(struct drm_crtc *crtc)
 }
 
 static uint32_t ironlake_compute_dpll(struct intel_crtc *intel_crtc,
-				      intel_clock_t *clock, u32 *fp)
+				      intel_clock_t *clock, u32 *fp,
+				      intel_clock_t *reduced_clock, u32 *fp2)
 {
 	struct drm_crtc *crtc = &intel_crtc->base;
 	struct drm_device *dev = crtc->dev;
@@ -5511,6 +5512,9 @@ static uint32_t ironlake_compute_dpll(struct intel_crtc *intel_crtc,
 	if (clock->m < factor * clock->n)
 		*fp |= FP_CB_TUNE;
 
+	if (fp2 && (reduced_clock->m < factor * reduced_clock->n))
+		*fp2 |= FP_CB_TUNE;
+
 	dpll = 0;
 
 	if (is_lvds)
@@ -5626,7 +5630,8 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 		fp2 = reduced_clock.n << 16 | reduced_clock.m1 << 8 |
 			reduced_clock.m2;
 
-	dpll = ironlake_compute_dpll(intel_crtc, &clock, &fp);
+	dpll = ironlake_compute_dpll(intel_crtc, &clock, &fp, &reduced_clock,
+				     has_reduced_clock ? &fp2 : NULL);
 
 	DRM_DEBUG_KMS("Mode for pipe %d:\n", pipe);
 	drm_mode_debug_printmodeline(mode);