drm/i915: Split watermark level computation from the code

Refactor the watermarks computation for one level to a separate
function. This function will now set the ->enable flag to true,
even if the watermark level wasn't actually checked yet. In the
future we will delay the checking so we must consider all unchecked
watermarks as possibly valid.

v2: Preserve comment about latency units

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -2284,31 +2284,45 @@ static uint32_t ilk_compute_fbc_wm(struct hsw_pipe_wm_parameters *params,
 			  params->pri_bytes_per_pixel);
 }
 
+static void ilk_compute_wm_level(struct drm_i915_private *dev_priv,
+				 int level,
+				 struct hsw_pipe_wm_parameters *p,
+				 struct hsw_lp_wm_result *result)
+{
+	uint16_t pri_latency = dev_priv->wm.pri_latency[level];
+	uint16_t spr_latency = dev_priv->wm.spr_latency[level];
+	uint16_t cur_latency = dev_priv->wm.cur_latency[level];
+
+	/* WM1+ latency values stored in 0.5us units */
+	if (level > 0) {
+		pri_latency *= 5;
+		spr_latency *= 5;
+		cur_latency *= 5;
+	}
+
+	result->pri_val = ilk_compute_pri_wm(p, pri_latency, level);
+	result->spr_val = ilk_compute_spr_wm(p, spr_latency);
+	result->cur_val = ilk_compute_cur_wm(p, cur_latency);
+	result->fbc_val = ilk_compute_fbc_wm(p, result->pri_val);
+	result->enable = true;
+}
+
 static bool hsw_compute_lp_wm(struct drm_i915_private *dev_priv,
 			      int level, struct hsw_wm_maximums *max,
 			      struct hsw_pipe_wm_parameters *params,
 			      struct hsw_lp_wm_result *result)
 {
 	enum pipe pipe;
-	uint32_t pri_val[3], spr_val[3], cur_val[3], fbc_val[3];
-
-	for (pipe = PIPE_A; pipe <= PIPE_C; pipe++) {
-		struct hsw_pipe_wm_parameters *p = &params[pipe];
-		/* WM1+ latency values stored in 0.5us units */
-		uint16_t pri_latency = dev_priv->wm.pri_latency[level] * 5;
-		uint16_t spr_latency = dev_priv->wm.spr_latency[level] * 5;
-		uint16_t cur_latency = dev_priv->wm.cur_latency[level] * 5;
+	struct hsw_lp_wm_result res[3];
 
-		pri_val[pipe] = ilk_compute_pri_wm(p, pri_latency, true);
-		spr_val[pipe] = ilk_compute_spr_wm(p, spr_latency);
-		cur_val[pipe] = ilk_compute_cur_wm(p, cur_latency);
-		fbc_val[pipe] = ilk_compute_fbc_wm(p, pri_val[pipe]);
-	}
+	for (pipe = PIPE_A; pipe <= PIPE_C; pipe++)
+		ilk_compute_wm_level(dev_priv, level, &params[pipe], &res[pipe]);
 
-	result->pri_val = max3(pri_val[0], pri_val[1], pri_val[2]);
-	result->spr_val = max3(spr_val[0], spr_val[1], spr_val[2]);
-	result->cur_val = max3(cur_val[0], cur_val[1], cur_val[2]);
-	result->fbc_val = max3(fbc_val[0], fbc_val[1], fbc_val[2]);
+	result->pri_val = max3(res[0].pri_val, res[1].pri_val, res[2].pri_val);
+	result->spr_val = max3(res[0].spr_val, res[1].spr_val, res[2].spr_val);
+	result->cur_val = max3(res[0].cur_val, res[1].cur_val, res[2].cur_val);
+	result->fbc_val = max3(res[0].fbc_val, res[1].fbc_val, res[2].fbc_val);
+	result->enable = true;
 
 	if (result->fbc_val > max->fbc) {
 		result->fbc_enable = false;
@@ -2317,6 +2331,9 @@ static bool hsw_compute_lp_wm(struct drm_i915_private *dev_priv,
 		result->fbc_enable = true;
 	}
 
+	if (!result->enable)
+		return false;
+
 	result->enable = result->pri_val <= max->pri &&
 			 result->spr_val <= max->spr &&
 			 result->cur_val <= max->cur;