drm/i915/vlv: fix up broken precision in vlv_crtc_clock_get

commit 662c6ecb upstream.

With some divider values we end up with the wrong result.  So remove the
intermediates (like Ville suggested in the first place) to get the right
answer.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/i915/intel_display.c

@@ -5040,7 +5040,7 @@ static void vlv_crtc_clock_get(struct intel_crtc *crtc,
 	int pipe = pipe_config->cpu_transcoder;
 	intel_clock_t clock;
 	u32 mdiv;
-	int refclk = 100000, fastclk, update_rate;
+	int refclk = 100000;
 
 	mutex_lock(&dev_priv->dpio_lock);
 	mdiv = vlv_dpio_read(dev_priv, DPIO_DIV(pipe));
@@ -5052,10 +5052,8 @@ static void vlv_crtc_clock_get(struct intel_crtc *crtc,
 	clock.p1 = (mdiv >> DPIO_P1_SHIFT) & 7;
 	clock.p2 = (mdiv >> DPIO_P2_SHIFT) & 0x1f;
 
-	update_rate = refclk / clock.n;
-	clock.vco = update_rate * clock.m1 * clock.m2;
-	fastclk = clock.vco / clock.p1 / clock.p2;
-	clock.dot = (2 * fastclk);
+	clock.vco = refclk * clock.m1 * clock.m2 / clock.n;
+	clock.dot = 2 * clock.vco / (clock.p1 * clock.p2);
 
 	pipe_config->adjusted_mode.clock = clock.dot / 10;
 }