Use WAIT_FOR_SCAN_LINE instead of WAIT_FOR_VBLANK

Either way, the goal is tear-free video playing. But waiting for
a scan-line window not only has the advantage of being cheaper
for small windows, but also avoids hanging the GPU in the case
of the pipe getting turned off, (by screensaver, for example),
while a batch is waiting for a VBLANK that will never occur.

This fixes that GPU hang.
(cherry picked from commit bc3312fd7c03d09a231dfebfe390fe668ad15d1e)

2 files changed, 33 insertions, 22 deletions

diff --git a/src/i810_reg.h b/src/i810_reg.h
index 3114b42c..c9645691 100644
--- a/src/i810_reg.h
+++ b/src/i810_reg.h
@@ -2435,12 +2435,19 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #define MI_OVERLAY_FLIP_OFF		(2<<21)
 
 /* Wait for Events */
-#define MI_WAIT_FOR_EVENT		(0x03<<23)
-#define MI_WAIT_FOR_PIPEB_SVBLANK	(1<<18)
-#define MI_WAIT_FOR_PIPEA_SVBLANK	(1<<17)
-#define MI_WAIT_FOR_OVERLAY_FLIP	(1<<16)
-#define MI_WAIT_FOR_PIPEB_VBLANK	(1<<7)
-#define MI_WAIT_FOR_PIPEA_VBLANK	(1<<3)
+#define MI_WAIT_FOR_EVENT			(0x03<<23)
+#define MI_WAIT_FOR_PIPEB_SVBLANK		(1<<18)
+#define MI_WAIT_FOR_PIPEA_SVBLANK		(1<<17)
+#define MI_WAIT_FOR_OVERLAY_FLIP		(1<<16)
+#define MI_WAIT_FOR_PIPEB_VBLANK		(1<<7)
+#define MI_WAIT_FOR_PIPEB_SCAN_LINE_WINDOW	(1<<5)
+#define MI_WAIT_FOR_PIPEA_VBLANK		(1<<3)
+#define MI_WAIT_FOR_PIPEA_SCAN_LINE_WINDOW	(1<<2)
+
+/* Set the scan line for MI_WAIT_FOR_PIPE?_SCAN_LINE_WINDOW */
+#define MI_LOAD_SCAN_LINES_INCL			(0x12<<23)
+#define MI_LOAD_SCAN_LINES_DISPLAY_PIPEA	(0)
+#define MI_LOAD_SCAN_LINES_DISPLAY_PIPEB	(0x1<<20)
 
 /* Flush */
 #define MI_FLUSH			(0x04<<23)
diff --git a/src/i830_video.c b/src/i830_video.c
index 3f3aaacf..3dde5b4d 100644
--- a/src/i830_video.c
+++ b/src/i830_video.c
@@ -2533,24 +2533,28 @@ I830PutImage(ScrnInfoPtr pScrn,
         }
 
         if (sync) {
-            I830CrtcPrivatePtr intel_crtc = crtc->driver_private;
-            int event;
-
-            if (IS_I965G(pI830)) {
-                if (intel_crtc->pipe == 0)
-                    event = MI_WAIT_FOR_PIPEA_SVBLANK;
-                else
-                    event = MI_WAIT_FOR_PIPEB_SVBLANK;
-            } else {
-                if (intel_crtc->pipe == 0)
-                    event = MI_WAIT_FOR_PIPEA_VBLANK;
-                else
-                    event = MI_WAIT_FOR_PIPEB_VBLANK;
-            }
+	    BoxPtr box;
+            int event, pipe;
+	    I830CrtcPrivatePtr intel_crtc = crtc->driver_private;
+
+	    if (intel_crtc->pipe == 0) {
+		event = MI_WAIT_FOR_PIPEA_SCAN_LINE_WINDOW;
+		pipe = MI_LOAD_SCAN_LINES_DISPLAY_PIPEA;
+	    } else {
+		event = MI_WAIT_FOR_PIPEB_SCAN_LINE_WINDOW;
+		pipe = MI_LOAD_SCAN_LINES_DISPLAY_PIPEB;
+	    }
+
+	    box = REGION_EXTENTS(unused, clipBoxes);
 
-            BEGIN_BATCH(2);
+            BEGIN_BATCH(5);
+	    /* The documentation says that the LOAD_SCAN_LINES command
+	     * always comes in pairs. Don't ask me why. */
+	    OUT_BATCH(MI_LOAD_SCAN_LINES_INCL | pipe);
+	    OUT_BATCH((box->y1 << 16) | box->y2);
+	    OUT_BATCH(MI_LOAD_SCAN_LINES_INCL | pipe);
+	    OUT_BATCH((box->y1 << 16) | box->y2);
             OUT_BATCH(MI_WAIT_FOR_EVENT | event);
-            OUT_BATCH(MI_NOOP);
             ADVANCE_BATCH();
         }