drm/i915: set the IPS linetime watermark

Remove the "placeholder" comment and set the actual value described by
the specification. We still don't enable IPS, but it won't hurt to
already have the value set here.

While at it, fully set the register value instead of just masking the
values we're changing.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[danvet: Resolve conflict due to reordered patches.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -2079,31 +2079,23 @@ haswell_update_linetime_wm(struct drm_device *dev, struct drm_crtc *crtc)
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	enum pipe pipe = intel_crtc->pipe;
 	struct drm_display_mode *mode = &intel_crtc->config.adjusted_mode;
-	u32 temp;
+	u32 linetime, ips_linetime;
 
 	if (!intel_crtc_active(crtc)) {
 		I915_WRITE(PIPE_WM_LINETIME(pipe), 0);
 		return;
 	}
 
-	temp = I915_READ(PIPE_WM_LINETIME(pipe));
-	temp &= ~PIPE_WM_LINETIME_MASK;
-
 	/* The WM are computed with base on how long it takes to fill a single
 	 * row at the given clock rate, multiplied by 8.
 	 * */
-	temp |= PIPE_WM_LINETIME_TIME(
-		DIV_ROUND_CLOSEST(mode->htotal * 1000 * 8, mode->clock));
-
-	/* IPS watermarks are only used by pipe A, and are ignored by
-	 * pipes B and C.  They are calculated similarly to the common
-	 * linetime values, except that we are using CD clock frequency
-	 * in MHz instead of pixel rate for the division.
-	 *
-	 * This is a placeholder for the IPS watermark calculation code.
-	 */
+	linetime = DIV_ROUND_CLOSEST(mode->htotal * 1000 * 8, mode->clock);
+	ips_linetime = DIV_ROUND_CLOSEST(mode->htotal * 1000 * 8,
+					 intel_ddi_get_cdclk_freq(dev_priv));
 
-	I915_WRITE(PIPE_WM_LINETIME(pipe), temp);
+	I915_WRITE(PIPE_WM_LINETIME(pipe),
+		   PIPE_WM_LINETIME_IPS_LINETIME(ips_linetime) |
+		   PIPE_WM_LINETIME_TIME(linetime));
 }
 
 static void haswell_update_wm(struct drm_device *dev)