The transition watermarks ask for Selected Result Blocks (the real
value), not Result Blocks (the integer value). Given how ceilings are
applied in both the non-transition and the transition watermarks
calculations, we can get away with assuming that Selected Result
Blocks is actually Result Blocks minus 1 without any rounding errors.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_pm.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 40ce99c455f3..14f13a371989 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4874,7 +4874,7 @@ static void skl_compute_transition_wm(struct intel_crtc_state *cstate,
const struct drm_i915_private *dev_priv = to_i915(dev);
uint16_t trans_min, trans_y_tile_min;
const uint16_t trans_amount = 10; /* This is configurable amount */
- uint16_t trans_offset_b, res_blocks;
+ uint16_t wm0_sel_res_b, trans_offset_b, res_blocks;
if (!cstate->base.active)
goto exit;
@@ -4893,13 +4893,25 @@ static void skl_compute_transition_wm(struct intel_crtc_state *cstate,
trans_offset_b = trans_min + trans_amount;
+ /*
+ * The spec asks for Selected Result Blocks for wm0 (the real value),
+ * not Result Blocks (the integer value). Pay attention to the capital
+ * letters. The value wm_l0->plane_res_b is actually Result Blocks, but
+ * since Result Blocks is the ceiling of Selected Result Blocks plus 1,
+ * and since we later will have to get the ceiling of the sum in the
+ * transition watermarks calculation, we can just pretend Selected
+ * Result Blocks is Result Blocks minus 1 and it should work for the
+ * current platforms.
+ */
+ wm0_sel_res_b = wm_l0->plane_res_b - 1;
+
if (wp->y_tiled) {
trans_y_tile_min = (uint16_t) mul_round_up_u32_fixed16(2,
wp->y_tile_minimum);
- res_blocks = max(wm_l0->plane_res_b, trans_y_tile_min) +
+ res_blocks = max(wm0_sel_res_b, trans_y_tile_min) +
trans_offset_b;
} else {
- res_blocks = wm_l0->plane_res_b + trans_offset_b;
+ res_blocks = wm0_sel_res_b + trans_offset_b;
/* WA BUG:1938466 add one block for non y-tile planes */
if (IS_CNL_REVID(dev_priv, CNL_REVID_A0, CNL_REVID_A0))
--
2.14.4
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