drm/exynos: modify wait_for_vblank of fimd

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 fimd.
Signed-off-by: Prathyush K <prathyush.k@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_fimd.c

@@ -100,6 +100,8 @@ struct fimd_context {
 	u32				vidcon1;
 	bool				suspended;
 	struct mutex			lock;
+	wait_queue_head_t		wait_vsync_queue;
+	atomic_t			wait_vsync_event;
 
 	struct exynos_drm_panel_info *panel;
 };
@@ -311,11 +313,19 @@ static void fimd_disable_vblank(struct device *dev)
 static void fimd_wait_for_vblank(struct device *dev)
 {
 	struct fimd_context *ctx = get_fimd_context(dev);
-	int ret;
 
-	ret = wait_for((__raw_readl(ctx->regs + VIDCON1) &
-					VIDCON1_VSTATUS_VSYNC), 50);
-	if (ret < 0)
+	if (ctx->suspended)
+		return;
+
+	atomic_set(&ctx->wait_vsync_event, 1);
+
+	/*
+	 * wait for FIMD to signal VSYNC interrupt or return after
+	 * timeout which is set to 50ms (refresh rate of 20).
+	 */
+	if (!wait_event_timeout(ctx->wait_vsync_queue,
+				!atomic_read(&ctx->wait_vsync_event),
+				DRM_HZ/20))
 		DRM_DEBUG_KMS("vblank wait timed out.\n");
 }
 
@@ -667,6 +677,11 @@ static irqreturn_t fimd_irq_handler(int irq, void *dev_id)
 	drm_handle_vblank(drm_dev, manager->pipe);
 	fimd_finish_pageflip(drm_dev, manager->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:
 	return IRQ_HANDLED;
 }
@@ -885,6 +900,8 @@ static int __devinit fimd_probe(struct platform_device *pdev)
 	ctx->vidcon1 = pdata->vidcon1;
 	ctx->default_win = pdata->default_win;
 	ctx->panel = panel;
+	DRM_INIT_WAITQUEUE(&ctx->wait_vsync_queue);
+	atomic_set(&ctx->wait_vsync_event, 0);
 
 	subdrv = &ctx->subdrv;