linux-kernel - [PATCH] host1x: cdma: use completion instead of semaphore

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Message-Id: <20181210215119.1903413-1-arnd@arndb.de>
Date:   Mon, 10 Dec 2018 22:51:04 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Mikko Perttunen <cyndis@...si.fi>,
        Dmitry Osipenko <digetx@...il.com>,
        Emil Goode <emil.fsw@...de.io>,
        dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] host1x: cdma: use completion instead of semaphore

In this usage, the two are completely equivalent, but the
completion documents better what is going on, and we generally
try to avoid semaphores these days.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/gpu/host1x/cdma.c | 6 +++---
 drivers/gpu/host1x/cdma.h | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/host1x/cdma.c b/drivers/gpu/host1x/cdma.c
index 6bfb3e6f43d7..bdc80a303cec 100644
--- a/drivers/gpu/host1x/cdma.c
+++ b/drivers/gpu/host1x/cdma.c
@@ -204,7 +204,7 @@ unsigned int host1x_cdma_wait_locked(struct host1x_cdma *cdma,
 		cdma->event = event;
 
 		mutex_unlock(&cdma->lock);
-		down(&cdma->sem);
+		wait_for_completion(&cdma->complete);
 		mutex_lock(&cdma->lock);
 	}
 
@@ -308,7 +308,7 @@ static void update_cdma_locked(struct host1x_cdma *cdma)
 
 	if (signal) {
 		cdma->event = CDMA_EVENT_NONE;
-		up(&cdma->sem);
+		complete(&cdma->complete);
 	}
 }
 
@@ -410,7 +410,7 @@ int host1x_cdma_init(struct host1x_cdma *cdma)
 	int err;
 
 	mutex_init(&cdma->lock);
-	sema_init(&cdma->sem, 0);
+	init_completion(&cdma->complete);
 
 	INIT_LIST_HEAD(&cdma->sync_queue);
 
diff --git a/drivers/gpu/host1x/cdma.h b/drivers/gpu/host1x/cdma.h
index c628070b94d7..ba790f9bfebc 100644
--- a/drivers/gpu/host1x/cdma.h
+++ b/drivers/gpu/host1x/cdma.h
@@ -20,7 +20,7 @@
 #define __HOST1X_CDMA_H
 
 #include <linux/sched.h>
-#include <linux/semaphore.h>
+#include <linux/completion.h>
 #include <linux/list.h>
 
 struct host1x_syncpt;
@@ -70,7 +70,7 @@ enum cdma_event {
 
 struct host1x_cdma {
 	struct mutex lock;		/* controls access to shared state */
-	struct semaphore sem;		/* signalled when event occurs */
+	struct completion complete;	/* signalled when event occurs */
 	enum cdma_event event;		/* event that sem is waiting for */
 	unsigned int slots_used;	/* pb slots used in current submit */
 	unsigned int slots_free;	/* pb slots free in current submit */
-- 
2.20.0