intel: Restore manual flush for old kernels

Daniel Vetter pointed out that the automagic flush by the kernel for the
busy-ioctl was only introduced upstream in 2.6.37. So we still need to
manually emit a flush on old kernels.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/intel.h

@@ -425,6 +425,8 @@ typedef struct intel_screen_private {
 	Bool use_pageflipping;
 	Bool force_fallback;
 	Bool can_blt;
+	Bool has_kernel_flush;
+	Bool needs_flush;
 	Bool use_shadow;
 
 	/* Broken-out options. */

src/intel_batchbuffer.c

@@ -175,6 +175,13 @@ void intel_batch_emit_flush(ScrnInfoPtr scrn)
 	intel_batch_do_flush(scrn);
 }
 
+static Bool intel_batch_needs_flush(intel_screen_private *intel)
+{
+	ScreenPtr screen = intel->scrn->pScreen;
+	PixmapPtr pixmap = screen->GetScreenPixmap(screen);
+	return intel_get_pixmap_private(pixmap)->batch_write;
+}
+
 void intel_batch_submit(ScrnInfoPtr scrn)
 {
 	intel_screen_private *intel = intel_get_screen_private(scrn);
@@ -234,6 +241,8 @@ void intel_batch_submit(ScrnInfoPtr scrn)
 		}
 	}
 
+	intel->needs_flush |= intel_batch_needs_flush(intel);
+
 	while (!list_is_empty(&intel->batch_pixmaps)) {
 		struct intel_pixmap *entry;
 

src/intel_driver.c

@@ -448,6 +448,23 @@ static void I830XvInit(ScrnInfoPtr scrn)
 		   intel->colorKey);
 }
 
+static Bool has_kernel_flush(struct intel_screen_private *intel)
+{
+	drm_i915_getparam_t gp;
+	int value;
+
+	/* The BLT ring was introduced at the same time as the
+	 * automatic flush for the busy-ioctl.
+	 */
+
+	gp.value = &value;
+	gp.param = I915_PARAM_HAS_BLT;
+	if (drmIoctl(intel->drmSubFD, DRM_IOCTL_I915_GETPARAM, &gp))
+		return FALSE;
+
+	return value;
+}
+
 static Bool can_accelerate_blt(struct intel_screen_private *intel)
 {
 	if (0 && (IS_I830(intel) || IS_845G(intel))) {
@@ -597,6 +614,7 @@ static Bool I830PreInit(ScrnInfoPtr scrn, int flags)
 		intel->tiling &= ~INTEL_TILING_FB;
 
 	intel->can_blt = can_accelerate_blt(intel);
+	intel->has_kernel_flush = has_kernel_flush(intel);
 	intel->use_shadow = !intel->can_blt;
 
 	if (xf86IsOptionSet(intel->Options, OPTION_SHADOW)) {

src/intel_uxa.c

@@ -937,7 +937,18 @@ static Bool intel_uxa_get_image(PixmapPtr pixmap,
 
 static void intel_flush_rendering(intel_screen_private *intel)
 {
-    drm_intel_bo_busy(intel->front_buffer);
+	if (intel->needs_flush == 0)
+		return;
+
+	if (intel->has_kernel_flush) {
+		intel_batch_submit(intel->scrn);
+		drm_intel_bo_busy(intel->front_buffer);
+	} else {
+		intel_batch_emit_flush(intel->scrn);
+		intel_batch_submit(intel->scrn);
+	}
+
+	intel->needs_flush = 0;
 }
 
 void intel_uxa_block_handler(intel_screen_private *intel)