linux-kernel - [patch v2] net: hip04: Make tx coalesce timer actually work

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Message-ID: <alpine.DEB.2.11.1504142140290.3845@nanos>
Date:	Tue, 14 Apr 2015 21:42:42 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Miller <davem@...emloft.net>
cc:	arnd@...db.de, linux-kernel@...r.kernel.org, peterz@...radead.org,
	mingo@...nel.org, dingtianhong@...wei.com, zhangfei.gao@...aro.org,
	dan.carpenter@...cle.com, netdev@...r.kernel.org
Subject: [patch v2] net: hip04: Make tx coalesce timer actually work

The code sets the expiry value of the timer to a relative value and
starts it with hrtimer_start_expires. That's fine, but that only works
once. The timer is started in relative mode, so the expiry value gets
overwritten with the absolut expiry time (now + expiry).

So once the timer expired, a new call to hrtimer_start_expires results
in an immidiately expired timer, because the expiry value is
already in the past.

Use the proper mechanisms to (re)start the timer in the intended way.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: dingtianhong <dingtianhong@...wei.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Zhangfei Gao <zhangfei.gao@...aro.org>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Cc: netdev@...r.kernel.org
---
 drivers/net/ethernet/hisilicon/hip04_eth.c |   18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

Index: linux/drivers/net/ethernet/hisilicon/hip04_eth.c
===================================================================
--- linux.orig/drivers/net/ethernet/hisilicon/hip04_eth.c
+++ linux/drivers/net/ethernet/hisilicon/hip04_eth.c
@@ -413,6 +413,15 @@ out:
 	return count;
 }
 
+static void hip04_start_tx_timer(struct hip04_priv *priv)
+{
+	unsigned long ns = priv->tx_coalesce_usecs * NSEC_PER_USEC / 2;
+
+	/* allow timer to fire after half the time at the earliest */
+	hrtimer_start_range_ns(&priv->tx_coalesce_timer, ns_to_ktime(ns),
+			       ns, HRTIMER_MODE_REL);
+}
+
 static int hip04_mac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 {
 	struct hip04_priv *priv = netdev_priv(ndev);
@@ -466,8 +475,7 @@ static int hip04_mac_start_xmit(struct s
 		}
 	} else if (!hrtimer_is_queued(&priv->tx_coalesce_timer)) {
 		/* cleanup not pending yet, start a new timer */
-		hrtimer_start_expires(&priv->tx_coalesce_timer,
-				      HRTIMER_MODE_REL);
+		hip04_start_tx_timer(priv);
 	}
 
 	return NETDEV_TX_OK;
@@ -549,7 +557,7 @@ done:
 	/* clean up tx descriptors and start a new timer if necessary */
 	tx_remaining = hip04_tx_reclaim(ndev, false);
 	if (rx < budget && tx_remaining)
-		hrtimer_start_expires(&priv->tx_coalesce_timer, HRTIMER_MODE_REL);
+		hip04_start_tx_timer(priv);
 
 	return rx;
 }
@@ -809,7 +817,6 @@ static int hip04_mac_probe(struct platfo
 	struct hip04_priv *priv;
 	struct resource *res;
 	unsigned int irq;
-	ktime_t txtime;
 	int ret;
 
 	ndev = alloc_etherdev(sizeof(struct hip04_priv));
@@ -846,9 +853,6 @@ static int hip04_mac_probe(struct platfo
 	 */
 	priv->tx_coalesce_frames = TX_DESC_NUM * 3 / 4;
 	priv->tx_coalesce_usecs = 200;
-	/* allow timer to fire after half the time at the earliest */
-	txtime = ktime_set(0, priv->tx_coalesce_usecs * NSEC_PER_USEC / 2);
-	hrtimer_set_expires_range(&priv->tx_coalesce_timer, txtime, txtime);
 	priv->tx_coalesce_timer.function = tx_done;
 
 	priv->map = syscon_node_to_regmap(arg.np);
--
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