drm/exynos: modify wait_for_vblank of mixer

It is more optimium to use wait queues while waiting for vsync so
that the current task is put to sleep. This way, the task wont
hog the CPU while waiting. We use wait_event_timeout and not
an interruptible function since we dont want the function to exit
when a signal is pending (e.g. drm release). This patch modifies
the wait for vblank function of mixer.
Signed-off-by: NPrathyush K <prathyush.k@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_mixer.c

@@ -93,6 +93,8 @@ struct mixer_context {
 	struct hdmi_win_data	win_data[MIXER_WIN_NR];
 	enum mixer_version_id	mxr_ver;
 	void			*parent_ctx;
+	wait_queue_head_t	wait_vsync_queue;
+	atomic_t		wait_vsync_event;
 };
 
 struct mixer_drv_data {
@@ -876,12 +878,23 @@ static void mixer_win_disable(void *ctx, int win)
 static void mixer_wait_for_vblank(void *ctx)
 {
 	struct mixer_context *mixer_ctx = ctx;
-	struct mixer_resources *res = &mixer_ctx->mixer_res;
-	int ret;
 
-	ret = wait_for((mixer_reg_read(res, MXR_INT_STATUS) &
-				MXR_INT_STATUS_VSYNC), 50);
-	if (ret < 0)
+	mutex_lock(&mixer_ctx->mixer_mutex);
+	if (!mixer_ctx->powered) {
+		mutex_unlock(&mixer_ctx->mixer_mutex);
+		return;
+	}
+	mutex_unlock(&mixer_ctx->mixer_mutex);
+
+	atomic_set(&mixer_ctx->wait_vsync_event, 1);
+
+	/*
+	 * wait for MIXER to signal VSYNC interrupt or return after
+	 * timeout which is set to 50ms (refresh rate of 20).
+	 */
+	if (!wait_event_timeout(mixer_ctx->wait_vsync_queue,
+				!atomic_read(&mixer_ctx->wait_vsync_event),
+				DRM_HZ/20))
 		DRM_DEBUG_KMS("vblank wait timed out.\n");
 }
 
@@ -957,6 +970,12 @@ static irqreturn_t mixer_irq_handler(int irq, void *arg)
 
 		drm_handle_vblank(drm_hdmi_ctx->drm_dev, ctx->pipe);
 		mixer_finish_pageflip(drm_hdmi_ctx->drm_dev, ctx->pipe);
+
+		/* set wait vsync event to zero and wake up queue. */
+		if (atomic_read(&ctx->wait_vsync_event)) {
+			atomic_set(&ctx->wait_vsync_event, 0);
+			DRM_WAKEUP(&ctx->wait_vsync_queue);
+		}
 	}
 
 out:
@@ -1139,6 +1158,8 @@ static int __devinit mixer_probe(struct platform_device *pdev)
 	drm_hdmi_ctx->ctx = (void *)ctx;
 	ctx->vp_enabled = drv->is_vp_enabled;
 	ctx->mxr_ver = drv->version;
+	DRM_INIT_WAITQUEUE(&ctx->wait_vsync_queue);
+	atomic_set(&ctx->wait_vsync_event, 0);
 
 	platform_set_drvdata(pdev, drm_hdmi_ctx);