netdev - [PATCH v4 36/36] net/mvpp2: Replace tasklet with softirq hrtimer

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Date:   Thu, 21 Dec 2017 11:42:05 +0100
From:   Anna-Maria Gleixner <anna-maria@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, keescook@...omium.org,
        Christoph Hellwig <hch@....de>,
        John Stultz <john.stultz@...aro.org>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: [PATCH v4 36/36] net/mvpp2: Replace tasklet with softirq hrtimer

From: Thomas Gleixner <tglx@...utronix.de>

The tx_done_tasklet tasklet is used in invoke the hrtimer
(mvpp2_hr_timer_cb) in softirq context. This can be also achieved without
the tasklet but with HRTIMER_MODE_SOFT as hrtimer mode.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>
Cc: Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Cc: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>
---
 drivers/net/ethernet/marvell/mvpp2.c | 62 +++++++++++++++---------------------
 1 file changed, 25 insertions(+), 37 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2.c b/drivers/net/ethernet/marvell/mvpp2.c
index 634b2f41cc9e..41f12961e4d1 100644
--- a/drivers/net/ethernet/marvell/mvpp2.c
+++ b/drivers/net/ethernet/marvell/mvpp2.c
@@ -901,9 +901,8 @@ struct mvpp2_pcpu_stats {
 /* Per-CPU port control */
 struct mvpp2_port_pcpu {
 	struct hrtimer tx_done_timer;
+	struct net_device *dev;
 	bool timer_scheduled;
-	/* Tasklet for egress finalization */
-	struct tasklet_struct tx_done_tasklet;
 };
 
 struct mvpp2_queue_vector {
@@ -6156,46 +6155,34 @@ static void mvpp2_link_event(struct net_device *dev)
 	}
 }
 
-static void mvpp2_timer_set(struct mvpp2_port_pcpu *port_pcpu)
-{
-	ktime_t interval;
-
-	if (!port_pcpu->timer_scheduled) {
-		port_pcpu->timer_scheduled = true;
-		interval = MVPP2_TXDONE_HRTIMER_PERIOD_NS;
-		hrtimer_start(&port_pcpu->tx_done_timer, interval,
-			      HRTIMER_MODE_REL_PINNED);
-	}
-}
-
-static void mvpp2_tx_proc_cb(unsigned long data)
+static enum hrtimer_restart mvpp2_hr_timer_cb(struct hrtimer *timer)
 {
-	struct net_device *dev = (struct net_device *)data;
-	struct mvpp2_port *port = netdev_priv(dev);
-	struct mvpp2_port_pcpu *port_pcpu = this_cpu_ptr(port->pcpu);
+	struct net_device *dev;
+	struct mvpp2_port *port;
+	struct mvpp2_port_pcpu *port_pcpu;
 	unsigned int tx_todo, cause;
 
+	port_pcpu = container_of(timer, struct mvpp2_port_pcpu, tx_done_timer);
+	dev = port_pcpu->dev;
+
 	if (!netif_running(dev))
-		return;
+		return HRTIMER_NORESTART;
+
 	port_pcpu->timer_scheduled = false;
+	port = netdev_priv(dev);
 
 	/* Process all the Tx queues */
 	cause = (1 << port->ntxqs) - 1;
 	tx_todo = mvpp2_tx_done(port, cause, smp_processor_id());
 
 	/* Set the timer in case not all the packets were processed */
-	if (tx_todo)
-		mvpp2_timer_set(port_pcpu);
-}
-
-static enum hrtimer_restart mvpp2_hr_timer_cb(struct hrtimer *timer)
-{
-	struct mvpp2_port_pcpu *port_pcpu = container_of(timer,
-							 struct mvpp2_port_pcpu,
-							 tx_done_timer);
-
-	tasklet_schedule(&port_pcpu->tx_done_tasklet);
+	if (tx_todo && !port_pcpu->timer_scheduled) {
+		port_pcpu->timer_scheduled = true;
+		hrtimer_forward_now(&port_pcpu->tx_done_timer,
+				    MVPP2_TXDONE_HRTIMER_PERIOD_NS);
 
+		return HRTIMER_RESTART;
+	}
 	return HRTIMER_NORESTART;
 }
 
@@ -6673,7 +6660,12 @@ static int mvpp2_tx(struct sk_buff *skb, struct net_device *dev)
 	    txq_pcpu->count > 0) {
 		struct mvpp2_port_pcpu *port_pcpu = this_cpu_ptr(port->pcpu);
 
-		mvpp2_timer_set(port_pcpu);
+		if (!port_pcpu->timer_scheduled) {
+			port_pcpu->timer_scheduled = true;
+			hrtimer_start(&port_pcpu->tx_done_timer,
+				      MVPP2_TXDONE_HRTIMER_PERIOD_NS,
+				      HRTIMER_MODE_REL_PINNED_SOFT);
+		}
 	}
 
 	return NETDEV_TX_OK;
@@ -7108,7 +7100,6 @@ static int mvpp2_stop(struct net_device *dev)
 
 			hrtimer_cancel(&port_pcpu->tx_done_timer);
 			port_pcpu->timer_scheduled = false;
-			tasklet_kill(&port_pcpu->tx_done_tasklet);
 		}
 	}
 	mvpp2_cleanup_rxqs(port);
@@ -7899,13 +7890,10 @@ static int mvpp2_port_probe(struct platform_device *pdev,
 			port_pcpu = per_cpu_ptr(port->pcpu, cpu);
 
 			hrtimer_init(&port_pcpu->tx_done_timer, CLOCK_MONOTONIC,
-				     HRTIMER_MODE_REL_PINNED);
+				     HRTIMER_MODE_REL_PINNED_SOFT);
 			port_pcpu->tx_done_timer.function = mvpp2_hr_timer_cb;
 			port_pcpu->timer_scheduled = false;
-
-			tasklet_init(&port_pcpu->tx_done_tasklet,
-				     mvpp2_tx_proc_cb,
-				     (unsigned long)dev);
+			port_pcpu->dev = dev;
 		}
 	}
 
-- 
2.11.0