[PATCH v4] drm/i915/bxt: Implement Transition WM

["Kumar, Mahesh" <mahesh1.kumar@intel.com>]

From: Mahesh Kumar <mahesh1.kumar@intel.com>

This patch enables Transition WM for SKL+ platforms.

Transition WM are used if IPC is enabled, to decide, number of blocks
to be fetched before reducing the priority of display to fetch from
memory.

Changes since v1:
 - Don't enable transition WM for GEN9 (Art/Paulo)
 - Rebase to use fixed point 16.16 calculation
 - Fix the use of selected result from latency level-0

Changes since v2:
 - Fix transition WM enable condition

Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 60 ++++++++++++++++++++++++++++++++++++++---
 1 file changed, 57 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index de2e738..4814a1a 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2862,6 +2862,8 @@ bool ilk_disable_lp_wm(struct drm_device *dev)
 
 #define SKL_DDB_SIZE		896	/* in blocks */
 #define BXT_DDB_SIZE		512
+#define SKL_TRANS_WM_AMOUNT	10	/* tunable value */
+#define SKL_TRANS_WM_MIN	14
 #define SKL_SAGV_BLOCK_TIME	30 /* µs */
 
 /*
@@ -3583,6 +3585,48 @@ static uint32_t skl_adjusted_plane_pixel_rate(const struct intel_crtc_state *cst
 	return pixel_rate;
 }
 
+static void skl_compute_plane_trans_wm(const struct drm_i915_private *dev_priv,
+					struct skl_pipe_wm *pipe_wm,
+					struct intel_plane_state *intel_pstate,
+					uint32_t selected_result,
+					uint32_t y_tile_min,
+					bool y_tile)
+{
+	struct drm_plane_state *pstate = &intel_pstate->base;
+	int id = skl_wm_plane_id(to_intel_plane(pstate->plane));
+	uint16_t *out_blocks = &pipe_wm->trans_wm.plane_res_b[id];
+	uint8_t *out_lines = &pipe_wm->trans_wm.plane_res_l[id];
+	uint32_t trans_min = 0, trans_offset_blocks;
+	uint32_t trans_y_tile_min = 0, res_blocks = 0;
+	uint16_t trans_res_blocks = 0;
+
+	/* Keep Trans WM disabled for GEN9 */
+	if (IS_GEN9(dev_priv))
+		goto exit;
+
+	trans_min = SKL_TRANS_WM_MIN;
+
+	trans_offset_blocks = (trans_min + SKL_TRANS_WM_AMOUNT) << 16;
+
+	if (y_tile) {
+		trans_y_tile_min = 2 * y_tile_min;
+		res_blocks = max(trans_y_tile_min, selected_result) +
+			trans_offset_blocks;
+	} else {
+		res_blocks = selected_result + trans_offset_blocks;
+	}
+
+	trans_res_blocks = DIV_ROUND_UP(res_blocks, 1 << 16) + 1;
+
+	/* WA BUG:1938466 add one block for non y-tile planes */
+	if (!y_tile)
+		trans_res_blocks += 1;
+exit:
+	*out_blocks = trans_res_blocks;
+	*out_lines = 0;
+}
+
+
 static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 				struct intel_crtc_state *cstate,
 				struct intel_plane_state *intel_pstate,
@@ -3709,6 +3753,9 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 	*out_blocks = res_blocks;
 	*out_lines = res_lines;
 
+	if (level == 0)
+		skl_compute_plane_trans_wm(dev_priv, pipe_wm, intel_pstate,
+				selected_result, y_tile_minimum, y_tiled);
 	return 0;
 }
 
@@ -3778,11 +3825,13 @@ skl_compute_linetime_wm(struct intel_crtc_state *cstate)
 }
 
 static void skl_compute_transition_wm(struct intel_crtc_state *cstate,
-				      struct skl_wm_level *trans_wm /* out */)
+				      struct skl_wm_level *trans_wm, /* out */
+				      struct skl_ddb_allocation *ddb)
 {
 	struct drm_crtc *crtc = cstate->base.crtc;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	struct intel_plane *intel_plane;
+	enum pipe pipe = to_intel_crtc(crtc)->pipe;
 
 	if (!cstate->base.active)
 		return;
@@ -3790,8 +3839,13 @@ static void skl_compute_transition_wm(struct intel_crtc_state *cstate,
 	/* Until we know more, just disable transition WMs */
 	for_each_intel_plane_on_crtc(crtc->dev, intel_crtc, intel_plane) {
 		int i = skl_wm_plane_id(intel_plane);
+		uint16_t plane_ddb = skl_ddb_entry_size(&ddb->plane[pipe][i]);
+		uint16_t trans_res_blocks = trans_wm->plane_res_b[i];
 
-		trans_wm->plane_en[i] = false;
+		if ((trans_res_blocks > 0) && (trans_res_blocks <= plane_ddb))
+			trans_wm->plane_en[i] = true;
+		else
+			trans_wm->plane_en[i] = false;
 	}
 }
 
@@ -3822,7 +3876,7 @@ static int skl_build_pipe_wm(struct intel_crtc_state *cstate,
 
 	pipe_wm->linetime = skl_compute_linetime_wm(cstate);
 
-	skl_compute_transition_wm(cstate, &pipe_wm->trans_wm);
+	skl_compute_transition_wm(cstate, &pipe_wm->trans_wm, ddb);
 
 	return 0;
 }
-- 
2.8.3

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