drm/i915/vlv: fix RC6 residency time calculation

The divider value to convert from CZ clock rate to ms needs a +1
adjustment on VLV just like on CHV. This matches both the spec and
the accuracy test by pm_rc6_residency.

v2:
- simplify logic checking for the CHV 320MHz special case (Rodrigo)

Testcase: igt/pm_rc6_residency
Signed-off-by: Imre Deak <imre.deak@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76877Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_sysfs.c

@@ -64,24 +64,16 @@ static u32 calc_residency(struct drm_device *dev, const u32 reg)
 			goto out;
 		}
 
-		units = 0;
-		div = 1000000ULL;
-
-		if (IS_CHERRYVIEW(dev)) {
+		if (IS_CHERRYVIEW(dev) && czcount_30ns == 1) {
 			/* Special case for 320Mhz */
-			if (czcount_30ns == 1) {
-				div = 10000000ULL;
-				units = 3125ULL;
-			} else {
-				/* chv counts are one less */
-				czcount_30ns += 1;
-			}
+			div = 10000000ULL;
+			units = 3125ULL;
+		} else {
+			czcount_30ns += 1;
+			div = 1000000ULL;
+			units = DIV_ROUND_UP_ULL(30ULL * bias, czcount_30ns);
 		}
 
-		if (units == 0)
-			units = DIV_ROUND_UP_ULL(30ULL * bias,
-						 (u64)czcount_30ns);
-
 		if (I915_READ(VLV_COUNTER_CONTROL) & VLV_COUNT_RANGE_HIGH)
 			units <<= 8;