bochs: add page_flip

Implement crtc page_flip callback for bochsdrm.  The qemu stdvga has no
vblank signaling, so we have to fake it.  We do so by instantly calling
drm_send_vblank_event.  Tested with kmscon.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/bochs/bochs_kms.c

@@ -109,11 +109,32 @@ static void bochs_crtc_gamma_set(struct drm_crtc *crtc, u16 *red, u16 *green,
 {
 }
 
+static int bochs_crtc_page_flip(struct drm_crtc *crtc,
+				struct drm_framebuffer *fb,
+				struct drm_pending_vblank_event *event,
+				uint32_t page_flip_flags)
+{
+	struct bochs_device *bochs =
+		container_of(crtc, struct bochs_device, crtc);
+	struct drm_framebuffer *old_fb = crtc->primary->fb;
+	unsigned long irqflags;
+
+	crtc->primary->fb = fb;
+	bochs_crtc_mode_set_base(crtc, 0, 0, old_fb);
+	if (event) {
+		spin_lock_irqsave(&bochs->dev->event_lock, irqflags);
+		drm_send_vblank_event(bochs->dev, -1, event);
+		spin_unlock_irqrestore(&bochs->dev->event_lock, irqflags);
+	}
+	return 0;
+}
+
 /* These provide the minimum set of functions required to handle a CRTC */
 static const struct drm_crtc_funcs bochs_crtc_funcs = {
 	.gamma_set = bochs_crtc_gamma_set,
 	.set_config = drm_crtc_helper_set_config,
 	.destroy = drm_crtc_cleanup,
+	.page_flip = bochs_crtc_page_flip,
 };
 
 static const struct drm_crtc_helper_funcs bochs_helper_funcs = {