drm/i915: Fix i855 get_display_clock_speed

Actually read the HPLLCC register insted of assuming it's 0. Fix the
HPLLCC bit definitions and all the missing ones from the 852GME spec.

852GME, 854 and 855 all seem to match the same HPLLC encoding even
though only some of the values are valid is some of the platforms.

v2: Rebased to the latest
v3: Rebased to the latest

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v1)
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Acked-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -50,12 +50,17 @@
 
 /* PCI config space */
 
-#define HPLLCC	0xc0 /* 855 only */
-#define   GC_CLOCK_CONTROL_MASK		(0xf << 0)
+#define HPLLCC	0xc0 /* 85x only */
+#define   GC_CLOCK_CONTROL_MASK		(0x7 << 0)
 #define   GC_CLOCK_133_200		(0 << 0)
 #define   GC_CLOCK_100_200		(1 << 0)
 #define   GC_CLOCK_100_133		(2 << 0)
-#define   GC_CLOCK_166_250		(3 << 0)
+#define   GC_CLOCK_133_266		(3 << 0)
+#define   GC_CLOCK_133_200_2		(4 << 0)
+#define   GC_CLOCK_133_266_2		(5 << 0)
+#define   GC_CLOCK_166_266		(6 << 0)
+#define   GC_CLOCK_166_250		(7 << 0)
+
 #define GCFGC2	0xda
 #define GCFGC	0xf0 /* 915+ only */
 #define   GC_LOW_FREQUENCY_ENABLE	(1 << 7)

drivers/gpu/drm/i915/intel_display.c

@@ -6822,20 +6822,29 @@ static int i865_get_display_clock_speed(struct drm_device *dev)
 	return 266667;
 }
 
-static int i855_get_display_clock_speed(struct drm_device *dev)
+static int i85x_get_display_clock_speed(struct drm_device *dev)
 {
 	u16 hpllcc = 0;
+
+	pci_bus_read_config_word(dev->pdev->bus,
+				 PCI_DEVFN(0, 3), HPLLCC, &hpllcc);
+
 	/* Assume that the hardware is in the high speed state.  This
 	 * should be the default.
 	 */
 	switch (hpllcc & GC_CLOCK_CONTROL_MASK) {
 	case GC_CLOCK_133_200:
+	case GC_CLOCK_133_200_2:
 	case GC_CLOCK_100_200:
 		return 200000;
 	case GC_CLOCK_166_250:
 		return 250000;
 	case GC_CLOCK_100_133:
 		return 133333;
+	case GC_CLOCK_133_266:
+	case GC_CLOCK_133_266_2:
+	case GC_CLOCK_166_266:
+		return 266667;
 	}
 
 	/* Shouldn't happen */
@@ -14399,8 +14408,8 @@ static void intel_init_display(struct drm_device *dev)
 			i865_get_display_clock_speed;
 	else if (IS_I85X(dev))
 		dev_priv->display.get_display_clock_speed =
-			i855_get_display_clock_speed;
-	else /* 852, 830 */
+			i85x_get_display_clock_speed;
+	else /* 830 */
 		dev_priv->display.get_display_clock_speed =
 			i830_get_display_clock_speed;