linux-kernel - [PATCH] drm/omap: panel-dsi-cm: Remove deprecated create_singlethread

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Message-ID: <20160702094708.GA31263@Karyakshetra>
Date:	Sat, 2 Jul 2016 15:17:08 +0530
From:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>
To:	David Airlie <airlied@...ux.ie>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Dave Airlie <airlied@...hat.com>,
	Rob Clark <robdclark@...il.com>, Arnd Bergmann <arnd@...db.de>
Cc:	Tejun Heo <tj@...nel.org>, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] drm/omap: panel-dsi-cm: Remove deprecated
 create_singlethread_workqueue

The workqueue "workqueue" has only a single workitem(&ddata->ulps_work) per
panel_drv_data 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.

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

Workitem is sync cancelled in dsicm_cancel_ulps_work() which is called
in dsicm_remove() to ensure that there are no workitems pending when the
driver is disconnected.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@...il.com>
---
 drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c b/drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c
index 2b11807..e614d5b 100644
--- a/drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c
+++ b/drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c
@@ -76,8 +76,6 @@ struct panel_drv_data {

 	bool intro_printed;

-	struct workqueue_struct *workqueue;
-
 	bool ulps_enabled;
 	unsigned ulps_timeout;
 	struct delayed_work ulps_work;
@@ -233,7 +231,7 @@ static int dsicm_set_update_window(struct panel_drv_data *ddata,
 static void dsicm_queue_ulps_work(struct panel_drv_data *ddata)
 {
 	if (ddata->ulps_timeout > 0)
-		queue_delayed_work(ddata->workqueue, &ddata->ulps_work,
+		schedule_delayed_work(&ddata->ulps_work,
 				msecs_to_jiffies(ddata->ulps_timeout));
 }

@@ -1245,11 +1243,6 @@ static int dsicm_probe(struct platform_device *pdev)
 		dev_dbg(dev, "Using GPIO TE\n");
 	}

-	ddata->workqueue = create_singlethread_workqueue("dsicm_wq");
-	if (ddata->workqueue == NULL) {
-		dev_err(dev, "can't create workqueue\n");
-		return -ENOMEM;
-	}
 	INIT_DELAYED_WORK(&ddata->ulps_work, dsicm_ulps_work);

 	dsicm_hw_reset(ddata);
@@ -1263,7 +1256,7 @@ static int dsicm_probe(struct platform_device *pdev)
 				dev, ddata, &dsicm_bl_ops, &props);
 		if (IS_ERR(bldev)) {
 			r = PTR_ERR(bldev);
-			goto err_bl;
+			goto err_reg;
 		}

 		ddata->bldev = bldev;
@@ -1286,8 +1279,6 @@ static int dsicm_probe(struct platform_device *pdev)
 err_sysfs_create:
 	if (bldev != NULL)
 		backlight_device_unregister(bldev);
-err_bl:
-	destroy_workqueue(ddata->workqueue);
 err_reg:
 	return r;
 }
@@ -1317,8 +1308,6 @@ static int __exit dsicm_remove(struct platform_device *pdev)
 	omap_dss_put_device(ddata->in);

 	dsicm_cancel_ulps_work(ddata);
-	destroy_workqueue(ddata->workqueue);
-
 	/* reset, to be sure that the panel is in a valid state */
 	dsicm_hw_reset(ddata);

--
2.1.4