[PATCH] drm/exynos: Remove deprecated create_singlethread_workqueue

[Bhaktipriya Shridhar]

The workqueue g2d_workq has only a single workitem(&g2d->runqueue_work)
and hence doesn't require ordering. Also, it is not being used on a
memory reclaim path. Hence, the singlethreaded workqueue has been
replaced with the use of system_wq.

System workqueues have been able to handle high level of concurrency
for a long time now and hence it's not required to have a singlethreaded
workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
created with create_singlethread_workqueue(), system_wq allows multiple
work items to overlap executions even on the same CPU; however, a
per-cpu workqueue doesn't have any CPU locality or global ordering
guarantee unless the target CPU is explicitly specified and thus the
increase of local concurrency shouldn't make any difference.

Occurences of the label err_destroy_workqueue have also been removed
because with the usage of system_wq, calls to destroy_workqueue() have
been dropped, which makes the label unnecessary.

Work item has been flushed in g2d_remove() to ensure that nothing is
pending when the driver disconnects.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@xxxxxxxxx>
---
 drivers/gpu/drm/exynos/exynos_drm_g2d.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
index 4935523..defb9d0 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
@@ -224,7 +224,6 @@ struct g2d_data {
 	struct clk			*gate_clk;
 	void __iomem			*regs;
 	int				irq;
-	struct workqueue_struct		*g2d_workq;
 	struct work_struct		runqueue_work;
 	struct exynos_drm_subdrv	subdrv;
 	bool				suspended;
@@ -921,7 +920,7 @@ static irqreturn_t g2d_irq_handler(int irq, void *dev_id)
 	}

 	if (pending & G2D_INTP_ACMD_FIN)
-		queue_work(g2d->g2d_workq, &g2d->runqueue_work);
+		schedule_work(&g2d->runqueue_work);

 	return IRQ_HANDLED;
 }
@@ -1380,13 +1379,6 @@ static int g2d_probe(struct platform_device *pdev)

 	g2d->dev = dev;

-	g2d->g2d_workq = create_singlethread_workqueue("g2d");
-	if (!g2d->g2d_workq) {
-		dev_err(dev, "failed to create workqueue\n");
-		ret = -EINVAL;
-		goto err_destroy_slab;
-	}
-
 	INIT_WORK(&g2d->runqueue_work, g2d_runqueue_worker);
 	INIT_LIST_HEAD(&g2d->free_cmdlist);
 	INIT_LIST_HEAD(&g2d->runqueue);
@@ -1398,7 +1390,7 @@ static int g2d_probe(struct platform_device *pdev)
 	if (IS_ERR(g2d->gate_clk)) {
 		dev_err(dev, "failed to get gate clock\n");
 		ret = PTR_ERR(g2d->gate_clk);
-		goto err_destroy_workqueue;
+		goto err_destroy_slab;
 	}

 	pm_runtime_enable(dev);
@@ -1449,8 +1441,6 @@ static int g2d_probe(struct platform_device *pdev)

 err_put_clk:
 	pm_runtime_disable(dev);
-err_destroy_workqueue:
-	destroy_workqueue(g2d->g2d_workq);
 err_destroy_slab:
 	kmem_cache_destroy(g2d->runqueue_slab);
 	return ret;
@@ -1471,7 +1461,7 @@ static int g2d_remove(struct platform_device *pdev)
 	pm_runtime_disable(&pdev->dev);

 	g2d_fini_cmdlist(g2d);
-	destroy_workqueue(g2d->g2d_workq);
+	flush_work(&g2d->runqueue_work);
 	kmem_cache_destroy(g2d->runqueue_slab);

 	return 0;
--
2.1.4