drm/i915: Make i9xx_crtc_clock_get() work for PCH DPLLs

Add the 120MHz refernce clock case for PCH DPLLs.

Also determine the reference clock frequency more accurately by
checking for the PLLB_REF_INPUT_SPREADSPECTRUMIN refclk input
mode. The gen2 code already checked it, but it stil assumed a
fixed 66MHz refclk. Instead we need to consult the VBT for the
real value.

v2: Fix refclk for SSC panel case

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -7341,6 +7341,22 @@ void intel_release_load_detect_pipe(struct drm_connector *connector,
 	mutex_unlock(&crtc->mutex);
 }
 
+static int i9xx_pll_refclk(struct drm_device *dev,
+			   const struct intel_crtc_config *pipe_config)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 dpll = pipe_config->dpll_hw_state.dpll;
+
+	if ((dpll & PLL_REF_INPUT_MASK) == PLLB_REF_INPUT_SPREADSPECTRUMIN)
+		return dev_priv->vbt.lvds_ssc_freq * 1000;
+	else if (HAS_PCH_SPLIT(dev))
+		return 120000;
+	else if (!IS_GEN2(dev))
+		return 96000;
+	else
+		return 48000;
+}
+
 /* Returns the clock of the currently programmed mode of the given pipe. */
 static void i9xx_crtc_clock_get(struct intel_crtc *crtc,
 				struct intel_crtc_config *pipe_config)
@@ -7351,6 +7367,7 @@ static void i9xx_crtc_clock_get(struct intel_crtc *crtc,
 	u32 dpll = pipe_config->dpll_hw_state.dpll;
 	u32 fp;
 	intel_clock_t clock;
+	int refclk = i9xx_pll_refclk(dev, pipe_config);
 
 	if ((dpll & DISPLAY_RATE_SELECT_FPA1) == 0)
 		fp = pipe_config->dpll_hw_state.fp0;
@@ -7390,9 +7407,9 @@ static void i9xx_crtc_clock_get(struct intel_crtc *crtc,
 		}
 
 		if (IS_PINEVIEW(dev))
-			pineview_clock(96000, &clock);
+			pineview_clock(refclk, &clock);
 		else
-			i9xx_clock(96000, &clock);
+			i9xx_clock(refclk, &clock);
 	} else {
 		bool is_lvds = (pipe == 1) && (I915_READ(LVDS) & LVDS_PORT_EN);
 
@@ -7400,13 +7417,6 @@ static void i9xx_crtc_clock_get(struct intel_crtc *crtc,
 			clock.p1 = ffs((dpll & DPLL_FPA01_P1_POST_DIV_MASK_I830_LVDS) >>
 				       DPLL_FPA01_P1_POST_DIV_SHIFT);
 			clock.p2 = 14;
-
-			if ((dpll & PLL_REF_INPUT_MASK) ==
-			    PLLB_REF_INPUT_SPREADSPECTRUMIN) {
-				/* XXX: might not be 66MHz */
-				i9xx_clock(66000, &clock);
-			} else
-				i9xx_clock(48000, &clock);
 		} else {
 			if (dpll & PLL_P1_DIVIDE_BY_TWO)
 				clock.p1 = 2;
@@ -7418,9 +7428,9 @@ static void i9xx_crtc_clock_get(struct intel_crtc *crtc,
 				clock.p2 = 4;
 			else
 				clock.p2 = 2;
-
-			i9xx_clock(48000, &clock);
 		}
+
+		i9xx_clock(refclk, &clock);
 	}
 
 	pipe_config->adjusted_mode.clock = clock.dot;