From 1217dbc88e0901e4a657ee51e2e3b7d00bb72b77 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 17 Apr 2014 21:04:15 +0100
Subject: [PATCH] sna: Support efficient cursor updates for old machines

Given a kernel patch to fix coherency of physical objects, we can use a
more efficient method for updating cursors.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 src/sna/sna_display.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/sna/sna_display.c b/src/sna/sna_display.c
index 12f1e8d2..251d305b 100644
--- a/src/sna/sna_display.c
+++ b/src/sna/sna_display.c
@@ -4366,6 +4366,7 @@ sna_cursor_pre_init(struct sna *sna)
 		uint64_t name;
 		uint64_t value;
 	} cap;
+	int v;
 
 	if (sna->mode.num_real_crtc == 0)
 		return;
@@ -4374,6 +4375,8 @@ sna_cursor_pre_init(struct sna *sna)
 #define DRM_CAP_CURSOR_WIDTH	8
 #define DRM_CAP_CURSOR_HEIGHT	9
 
+#define I915_PARAM_HAS_COHERENT_PHYS_GTT 29
+
 	sna->cursor.max_size = 64;
 
 	cap.value = 0;
@@ -4387,7 +4390,17 @@ sna_cursor_pre_init(struct sna *sna)
 		assert(sna->cursor.max_size == cap.value);
 #endif
 
-	sna->cursor.use_gtt = sna->kgem.gen >= 033;
+	v = -1; /* No param uses the sign bit, reserve it for errors */
+	if (sna->kgem.gen >= 033) {
+		v = 1;
+	} else {
+		drm_i915_getparam_t gp = {
+			I915_PARAM_HAS_COHERENT_PHYS_GTT,
+			&v,
+		};
+		(void)drmIoctl(sna->kgem.fd, DRM_IOCTL_I915_GETPARAM, &gp);
+	}
+	sna->cursor.use_gtt = v > 0;
 	DBG(("%s: cursor updates use_gtt?=%d\n",
 	     __FUNCTION__, sna->cursor.use_gtt));