[Intel-gfx] [PATCH] drm/i915/skl: distribute DDB based on panel resolution

[Mahesh Kumar]

We distribute DDB equally among all pipes irrespective of display
buffer requirement of each pipe. This leads to a situation where high
resolution y-tiled display can not be enabled with 2 low resolution
displays.

Main contributing factor for DDB requirement is width of the display.
This patch make changes to distribute ddb based on display width.
So display with higher width will get bigger chunk of DDB.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107113
Cc: raviraj.p.sitaram at intel.com
Signed-off-by: Mahesh Kumar <mahesh1.kumar at intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 55 +++++++++++++++++++++++++++++++----------
 1 file changed, 42 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 7312ecb73415..e092f0deb93d 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3814,8 +3814,14 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
 	struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct drm_crtc *for_crtc = cstate->base.crtc;
+	enum pipe for_pipe = to_intel_crtc(for_crtc)->pipe;
+	const struct drm_crtc_state *crtc_state;
+	const struct drm_crtc *crtc;
+	u32 pipe_width[I915_MAX_PIPES] = {0};
+	u32 total_width = 0, width_before_pipe = 0;
 	unsigned int pipe_size, ddb_size;
-	int nth_active_pipe;
+	u16 ddb_size_before_pipe;
+	u32 i;
 
 	if (WARN_ON(!state) || !cstate->base.active) {
 		alloc->start = 0;
@@ -3833,14 +3839,14 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
 				      *num_active, ddb);
 
 	/*
-	 * If the state doesn't change the active CRTC's, then there's
-	 * no need to recalculate; the existing pipe allocation limits
-	 * should remain unchanged.  Note that we're safe from racing
-	 * commits since any racing commit that changes the active CRTC
-	 * list would need to grab _all_ crtc locks, including the one
-	 * we currently hold.
+	 * If the state doesn't change the active CRTC's or there is no
+	 * modeset request, then there's no need to recalculate;
+	 * the existing pipe allocation limits should remain unchanged.
+	 * Note that we're safe from racing commits since any racing commit
+	 * that changes the active CRTC list or do modeset would need to
+	 * grab _all_ crtc locks, including the one we currently hold.
 	 */
-	if (!intel_state->active_pipe_changes) {
+	if (!intel_state->active_pipe_changes && !intel_state->modeset) {
 		/*
 		 * alloc may be cleared by clear_intel_crtc_state,
 		 * copy from old state to be sure
@@ -3849,10 +3855,33 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
 		return;
 	}
 
-	nth_active_pipe = hweight32(intel_state->active_crtcs &
-				    (drm_crtc_mask(for_crtc) - 1));
-	pipe_size = ddb_size / hweight32(intel_state->active_crtcs);
-	alloc->start = nth_active_pipe * ddb_size / *num_active;
+	/*
+	 * Watermark/ddb requirement highly depends upon width of the
+	 * framebuffer, So instead of allocating DDB equally among pipes
+	 * distribute DDB based on resolution/width of the display.
+	 */
+	for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
+		const struct drm_display_mode *adjusted_mode;
+		int hdisplay, vdisplay;
+		enum pipe pipe;
+
+		if (!crtc_state->enable)
+			continue;
+
+		pipe = to_intel_crtc(crtc)->pipe;
+		adjusted_mode = &crtc_state->adjusted_mode;
+		drm_mode_get_hv_timing(adjusted_mode, &hdisplay, &vdisplay);
+		pipe_width[pipe] = hdisplay;
+		total_width += pipe_width[pipe];
+
+		if (pipe < for_pipe)
+			width_before_pipe += pipe_width[pipe];
+	}
+
+	ddb_size_before_pipe = div_u64(ddb_size * width_before_pipe,
+				       total_width);
+	pipe_size = div_u64(ddb_size * pipe_width[for_pipe], total_width);
+	alloc->start = ddb_size_before_pipe;
 	alloc->end = alloc->start + pipe_size;
 }
 
@@ -5259,7 +5288,7 @@ skl_ddb_add_affected_pipes(struct drm_atomic_state *state, bool *changed)
 	 * any other display updates race with this transaction, so we need
 	 * to grab the lock on *all* CRTC's.
 	 */
-	if (intel_state->active_pipe_changes) {
+	if (intel_state->active_pipe_changes || intel_state->modeset) {
 		realloc_pipes = ~0;
 		intel_state->wm_results.dirty_pipes = ~0;
 	}
-- 
2.16.2