[PATCH 2/4] drm/i915/skl+: calculate ddb minimum allocation (v4)

[Matt Roper <matthew.d.roper@intel.com>]

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

don't always use 8 ddb as minimum, instead calculate using proper
algorithm.

v2: optimizations as per Matt's comments.

v3 (by Matt):
 - Fix boolean logic for !fb test in skl_ddb_min_alloc()
 - Adjust negative tiling format comparisons in skl_ddb_min_alloc() to
   improve readability.

v4 (by Matt):
 - Rebase onto recent atomic watermark changes
 - Slight tweaks to code flow to make the logic more closely match the
   description in the bspec.

Cc: matthew.d.roper@intel.com
Signed-off-by: Kumar, Mahesh <mahesh1.kumar@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 62 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 57 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 95f9bb5..d7165b5 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3038,6 +3038,61 @@ skl_get_total_relative_data_rate(struct intel_crtc_state *intel_cstate)
 	return total_data_rate;
 }
 
+static uint16_t
+skl_ddb_min_alloc(const struct drm_plane_state *pstate,
+		  const int y)
+{
+	struct drm_framebuffer *fb = pstate->fb;
+	struct intel_plane_state *intel_pstate = to_intel_plane_state(pstate);
+	uint32_t src_w, src_h;
+	uint32_t min_scanlines = 8;
+	uint8_t plane_bpp;
+
+	if (WARN_ON(!fb))
+		return 0;
+
+	/* For packed formats, no y-plane, return 0 */
+	if (y && fb->pixel_format != DRM_FORMAT_NV12)
+		return 0;
+
+	/* For Non Y-tile return 8-blocks */
+	if (fb->modifier[0] != I915_FORMAT_MOD_Y_TILED &&
+	    fb->modifier[0] != I915_FORMAT_MOD_Yf_TILED)
+		return 8;
+
+	src_w = drm_rect_width(&intel_pstate->src) >> 16;
+	src_h = drm_rect_height(&intel_pstate->src) >> 16;
+
+	if (intel_rotation_90_or_270(pstate->rotation))
+		swap(src_w, src_h);
+
+	/* Halve UV plane width and height for NV12 */
+	if (fb->pixel_format == DRM_FORMAT_NV12 && !y) {
+		src_w /= 2;
+		src_h /= 2;
+	}
+
+	plane_bpp = y ? drm_format_plane_cpp(fb->pixel_format, 0) :
+		drm_format_plane_cpp(fb->pixel_format, 1);
+
+	if (intel_rotation_90_or_270(pstate->rotation)) {
+		switch (plane_bpp) {
+		case 1:
+			min_scanlines = 32;
+			break;
+		case 2:
+			min_scanlines = 16;
+			break;
+		default:
+			WARN(1, "Unsupported pixel depth %u for rotation",
+			     plane_bpp);
+			min_scanlines = 32;
+		}
+	}
+
+	return DIV_ROUND_UP((4 * src_w * plane_bpp), 512) * min_scanlines/4 + 3;
+}
+
 static int
 skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
 		      struct skl_ddb_allocation *ddb /* out */)
@@ -3100,11 +3155,8 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
 			continue;
 		}
 
-		minimum[id] = 8;
-		if (pstate->fb->pixel_format == DRM_FORMAT_NV12)
-			y_minimum[id] = 8;
-		else
-			y_minimum[id] = 0;
+		minimum[id] = skl_ddb_min_alloc(pstate, 0);
+		y_minimum[id] = skl_ddb_min_alloc(pstate, 1);
 	}
 
 	for (i = 0; i < PLANE_CURSOR; i++) {
-- 
2.1.4

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