[Intel-gfx] [PATCH v4 1/8] drm/i915/skl+: use linetime latency instead of ddb size

[Kumar, Mahesh]

This patch make changes to use linetime latency instead of allocated
DDB size during plane watermark calculation in switch case, This is
required to implement new DDB allocation algorithm.

In New Algorithm DDB is allocated based on WM values, because of which
number of DDB blocks will not be available during WM calculation,
So this "linetime latency" is suggested by SV/HW team to use during
switch-case for WM blocks selection.

Changes since v1:
 - Rebase on top of Paulo's patch series
Changes since v2:
 - Fix if-else condition (pointed by Maarten)

Signed-off-by: "Kumar, Mahesh" <mahesh1.kumar at intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 7f1748a..098336d 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3616,10 +3616,14 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 	    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
 		selected_result = max(method2, y_tile_minimum);
 	} else {
+		uint32_t linetime_us = 0;
+
+		linetime_us = DIV_ROUND_UP(width * 1000,
+				skl_pipe_pixel_rate(cstate));
 		if ((cpp * cstate->base.adjusted_mode.crtc_htotal / 512 < 1) &&
 		    (plane_bytes_per_line / 512 < 1))
 			selected_result = method2;
-		else if ((ddb_allocation / plane_blocks_per_line) >= 1)
+		else if (latency >= linetime_us)
 			selected_result = min(method1, method2);
 		else
 			selected_result = method1;
-- 
2.10.1