[Intel-gfx] [PATCH 10/12] drm/i915: Support maxfifo with two planes on CHV

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

CHV supposedly does maxfifo mode even with two enabled
(primary/sprite) planes. Lets try to support that by halving the FIFO
size for the calculations and picking the smallest calculcated
watermark from the enabled planes.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index d29c02c..e6cbc24 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -907,6 +907,8 @@ static bool vlv_compute_sr_wm(struct drm_device *dev,
 	int num_planes = 0;
 	int fifo_size = 0;
 	struct intel_plane *plane;
+	/* CHV supports max fifo with two planes (1:1 split) */
+	int max_planes = IS_CHERRYVIEW(dev) ? 2 : 1;
 
 	wm->sr.cursor = wm->sr.plane = 0;
 
@@ -920,23 +922,33 @@ static bool vlv_compute_sr_wm(struct drm_device *dev,
 		fifo_size = INTEL_INFO(dev_priv)->num_pipes * 512 - 1;
 	}
 
-	if (fifo_size == 0 || num_planes > 1)
+	if (fifo_size == 0 || num_planes > max_planes)
 		return false;
 
+	if (num_planes)
+		fifo_size /= num_planes;
+
 	wm->sr.cursor = vlv_compute_wm(to_intel_crtc(crtc),
 				       to_intel_plane(crtc->cursor), 0x3f);
 
 	list_for_each_entry(plane, &dev->mode_config.plane_list, base.head) {
+		uint16_t sr_wm;
+
 		if (plane->base.type == DRM_PLANE_TYPE_CURSOR)
 			continue;
 
 		if (plane->pipe != pipe)
 			continue;
 
-		wm->sr.plane = vlv_compute_wm(to_intel_crtc(crtc),
-					      plane, fifo_size);
-		if (wm->sr.plane != 0)
-			break;
+		sr_wm = vlv_compute_wm(to_intel_crtc(crtc),
+				       plane, fifo_size);
+		if (sr_wm == 0)
+			continue;
+
+		if (wm->sr.plane == 0)
+			wm->sr.plane = sr_wm;
+		else
+			wm->sr.plane = min(wm->sr.plane, sr_wm);
 	}
 
 	return true;
-- 
2.0.5