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

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>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 5b52ab0..f52e6d4 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5084,7 +5084,7 @@ 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, pipe, DPIO_DIV(pipe));
@@ -5096,10 +5096,8 @@ 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->port_clock = clock.dot / 10;
 }