drm/i915/gen9: fix watermarks when using the pipe scaler

Luckily, the necessary adjustments for when we're using the scaler are
exactly the same as the ones needed on ILK+, so just reuse the
function we already have.

v2: Invert the patch order so stable backports get easier.

Cc: stable@vger.kernel.org
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1475872138-16194-1-git-send-email-paulo.r.zanoni@intel.com
(cherry picked from commit cfd7e3a20251b9ac95651d64556f87f86128a966)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -3470,12 +3470,6 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
 	return 0;
 }
 
-static uint32_t skl_pipe_pixel_rate(const struct intel_crtc_state *config)
-{
-	/* TODO: Take into account the scalers once we support them */
-	return config->base.adjusted_mode.crtc_clock;
-}
-
 /*
  * The max latency should be 257 (max the punit can code is 255 and we add 2us
  * for the read latency) and cpp should always be <= 8, so that
@@ -3526,7 +3520,7 @@ static uint32_t skl_adjusted_plane_pixel_rate(const struct intel_crtc_state *cst
 	 * Adjusted plane pixel rate is just the pipe's adjusted pixel rate
 	 * with additional adjustments for plane-specific scaling.
 	 */
-	adjusted_pixel_rate = skl_pipe_pixel_rate(cstate);
+	adjusted_pixel_rate = ilk_pipe_pixel_rate(cstate);
 	downscale_amount = skl_plane_downscale_amount(pstate);
 
 	pixel_rate = adjusted_pixel_rate * downscale_amount >> 16;
@@ -3738,11 +3732,11 @@ skl_compute_linetime_wm(struct intel_crtc_state *cstate)
 	if (!cstate->base.active)
 		return 0;
 
-	if (WARN_ON(skl_pipe_pixel_rate(cstate) == 0))
+	if (WARN_ON(ilk_pipe_pixel_rate(cstate) == 0))
 		return 0;
 
 	return DIV_ROUND_UP(8 * cstate->base.adjusted_mode.crtc_htotal * 1000,
-			    skl_pipe_pixel_rate(cstate));
+			    ilk_pipe_pixel_rate(cstate));
 }
 
 static void skl_compute_transition_wm(struct intel_crtc_state *cstate,