[Intel-gfx] [PATCH 14/16] drm/i915: Prefer the 5/6 DDB split when primary is disabled

[ville.syrjala at linux.intel.com]

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

When the primary plane is disabled, pick the 5/6 DDB split to give the
sprite as much FIFO space as possible.

The normal heuristic of just looking at the highest valid WM level won't
necessarily pick the optimal split since both splits might have the same
number of levels enabled.

Preferring the 5/6 split won't actually affect the watermarks here, but
it does give more FIFO space to the sprite leading to potentially longer
periods spent in LP1+ states since the FIFO takes longer to drain.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_drv.h |  1 +
 drivers/gpu/drm/i915/intel_pm.c  | 27 ++++++++++++++++++++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 2a3ad60..4575017 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -354,6 +354,7 @@ struct intel_pipe_wm {
 	uint32_t linetime;
 	bool fbc_wm_enabled;
 	bool pipe_enabled;
+	bool primary_enabled;
 	bool sprites_enabled;
 	bool sprites_scaled;
 };
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 17f1769..66af79d 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -1736,6 +1736,7 @@ struct ilk_wm_maximums {
 /* used in computing the new watermarks state */
 struct intel_wm_config {
 	unsigned int num_pipes_active;
+	bool primary_enabled;
 	bool sprites_enabled;
 	bool sprites_scaled;
 };
@@ -2212,6 +2213,7 @@ static void ilk_compute_wm_config(struct drm_device *dev,
 		if (!wm->pipe_enabled)
 			continue;
 
+		config->primary_enabled |= wm->primary_enabled;
 		config->sprites_enabled |= wm->sprites_enabled;
 		config->sprites_scaled |= wm->sprites_scaled;
 		config->num_pipes_active++;
@@ -2224,6 +2226,7 @@ static bool ilk_validate_pipe_wm(struct drm_device *dev,
 	/* LP0 watermark maximums depend on this pipe alone */
 	const struct intel_wm_config config = {
 		.num_pipes_active = 1,
+		.primary_enabled = pipe_wm->primary_enabled,
 		.sprites_enabled = pipe_wm->sprites_enabled,
 		.sprites_scaled = pipe_wm->sprites_scaled,
 	};
@@ -2247,6 +2250,7 @@ static bool intel_compute_pipe_wm(struct drm_crtc *crtc,
 	struct ilk_wm_maximums max;
 
 	pipe_wm->pipe_enabled = params->active;
+	pipe_wm->primary_enabled = params->pri.enabled;
 	pipe_wm->sprites_enabled = params->spr.enabled;
 	pipe_wm->sprites_scaled = params->spr.scaled;
 
@@ -2299,6 +2303,7 @@ static void ilk_wm_merge_intermediate(struct drm_device *dev,
 	int level, max_level = ilk_wm_max_level(dev);
 
 	a->pipe_enabled |= b->pipe_enabled;
+	a->primary_enabled |= b->primary_enabled;
 	a->sprites_enabled |= b->sprites_enabled;
 	a->sprites_scaled |= b->sprites_scaled;
 
@@ -2491,11 +2496,21 @@ static void ilk_compute_wm_results(struct drm_device *dev,
 	}
 }
 
-/* Find the result with the highest level enabled. Check for enable_fbc_wm in
- * case both are at the same level. Prefer r1 in case they're the same. */
+/*
+ * Find the result with the highest level enabled.
+ * When the max level for each result is the same, pick r2
+ * when the primary plane is disabled, otherwise prefer the
+ * result which has FBC WM enabled. All else being equal, pick
+ * r1.
+ *
+ * FIXME should ideally calculate the FIFO drain time for each
+ * plane, and determine which split has the chance to keep
+ * the memory asleep for longest.
+ */
 static struct intel_pipe_wm *ilk_find_best_result(struct drm_device *dev,
 						  struct intel_pipe_wm *r1,
-						  struct intel_pipe_wm *r2)
+						  struct intel_pipe_wm *r2,
+						  bool primary_enabled)
 {
 	int level, max_level = ilk_wm_max_level(dev);
 	int level1 = 0, level2 = 0;
@@ -2508,7 +2523,8 @@ static struct intel_pipe_wm *ilk_find_best_result(struct drm_device *dev,
 	}
 
 	if (level1 == level2) {
-		if (r2->fbc_wm_enabled && !r1->fbc_wm_enabled)
+		if (!primary_enabled ||
+		    (r2->fbc_wm_enabled && !r1->fbc_wm_enabled))
 			return r2;
 		else
 			return r1;
@@ -2866,7 +2882,8 @@ static void ilk_program_watermarks(struct drm_device *dev)
 		ilk_compute_wm_maximums(dev, 1, &config, INTEL_DDB_PART_5_6, &max);
 		ilk_wm_merge(dev, &config, &max, &lp_wm_5_6);
 
-		best_lp_wm = ilk_find_best_result(dev, &lp_wm_1_2, &lp_wm_5_6);
+		best_lp_wm = ilk_find_best_result(dev, &lp_wm_1_2, &lp_wm_5_6,
+						  config.primary_enabled);
 	} else {
 		best_lp_wm = &lp_wm_1_2;
 	}
-- 
1.8.5.5