staging: unisys: visornic: Convert to using napi

Switch the visornic over to use napi.  Currently there is a kernel
thread that sits and waits on a wait queue to get notified of incoming
virtual interrupts. It would be nice if we could handle frame reception
using the standard napi processing instead.  This patch creates our napi
instance and has the rx thread schedule it

Given that the unisys hypervisor currently requires that queue servicing
be done by a polling loop that wakes up every 2ms, lets instead also
convert that to a timer, which is simpler, and allows us to remove all
the thread starting and stopping code.

Signed-off-by: Neil Horman <nhorman@redhat.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/unisys/visornic/visornic_main.c

@@ -89,11 +89,6 @@ static struct visor_driver visornic_driver = {
 	.channel_interrupt = NULL,
 };
 
-struct visor_thread_info {
-	struct task_struct *task;
-	int id;
-};
-
 struct chanstat {
 	unsigned long got_rcv;
 	unsigned long got_enbdisack;
@@ -110,7 +105,6 @@ struct chanstat {
 
 struct visornic_devdata {
 	int devnum;
-	int thread_wait_ms;
 	unsigned short enabled;		/* 0 disabled 1 enabled to receive */
 	unsigned short enab_dis_acked;	/* NET_RCV_ENABLE/DISABLE acked by
 					 * IOPART
@@ -162,7 +156,6 @@ struct visornic_devdata {
 	bool server_change_state;	 /* Processing SERVER_CHANGESTATE msg */
 	bool going_away;		 /* device is being torn down */
 	struct dentry *eth_debugfs_dir;
-	struct visor_thread_info threadinfo;
 	u64 interrupts_rcvd;
 	u64 interrupts_notme;
 	u64 interrupts_disabled;
@@ -194,6 +187,9 @@ struct visornic_devdata {
 
 	int queuefullmsg_logged;
 	struct chanstat chstat;
+	struct timer_list irq_poll_timer;
+	struct napi_struct napi;
+	struct uiscmdrsp cmdrsp[SIZEOF_CMDRSP];
 };
 
 
@@ -202,6 +198,8 @@ struct visornic_devdata {
  */
 static LIST_HEAD(list_all_devices);
 static DEFINE_SPINLOCK(lock_all_devices);
+static int visornic_poll(struct napi_struct *napi, int budget);
+static void poll_for_irq(unsigned long v);
 
 /**
  *	visor_copy_fragsinfo_from_skb(
@@ -301,49 +299,6 @@ visor_copy_fragsinfo_from_skb(struct sk_buff *skb, unsigned int firstfraglen,
 	return count;
 }
 
-/**
- *	visort_thread_start - starts thread for the device
- *	@thrinfo: The thread to start
- *	@threadfn: Function the thread starts
- *	@thrcontext: Context to pass to the thread, i.e. devdata
- *	@name:	string describing name of thread
- *
- *	Starts a thread for the device, currently only thread is
- *	process_incoming_rsps
- *	Returns 0 on success;
- */
-static int visor_thread_start(struct visor_thread_info *thrinfo,
-			      int (*threadfn)(void *),
-			      void *thrcontext, char *name)
-{
-	/* used to stop the thread */
-	thrinfo->task = kthread_run(threadfn, thrcontext, "%s", name);
-	if (IS_ERR(thrinfo->task)) {
-		pr_debug("%s failed (%ld)\n",
-			 __func__, PTR_ERR(thrinfo->task));
-		thrinfo->id = 0;
-		return -EINVAL;
-	}
-	thrinfo->id = thrinfo->task->pid;
-	return 0;
-}
-
-/**
- *	visor_thread_stop - stop a thread for the device
- *	@thrinfo: The thread to stop
- *
- *	Stop the thread and wait for completion for a minute
- *	Returns void.
- */
-static void visor_thread_stop(struct visor_thread_info *thrinfo)
-{
-	if (!thrinfo->id)
-		return;	/* thread not running */
-
-	BUG_ON(kthread_stop(thrinfo->task));
-	thrinfo->id = 0;
-}
-
 static ssize_t enable_ints_write(struct file *file,
 				 const char __user *buffer,
 				 size_t count, loff_t *ppos)
@@ -373,8 +328,8 @@ visornic_serverdown_complete(struct visornic_devdata *devdata)
 
 	netdev = devdata->netdev;
 
-	/* Stop using datachan */
-	visor_thread_stop(&devdata->threadinfo);
+	/* Stop polling for interrupts */
+	del_timer_sync(&devdata->irq_poll_timer);
 
 	rtnl_lock();
 	dev_close(netdev);
@@ -538,9 +493,6 @@ visornic_disable_with_timeout(struct net_device *netdev, const int timeout)
 	unsigned long flags;
 	int wait = 0;
 
-	/* stop the transmit queue so nothing more can be transmitted */
-	netif_stop_queue(netdev);
-
 	/* send a msg telling the other end we are stopping incoming pkts */
 	spin_lock_irqsave(&devdata->priv_lock, flags);
 	devdata->enabled = 0;
@@ -586,10 +538,14 @@ visornic_disable_with_timeout(struct net_device *netdev, const int timeout)
 				break;
 		}
 	}
-
 	/* we've set enabled to 0, so we can give up the lock. */
 	spin_unlock_irqrestore(&devdata->priv_lock, flags);
 
+	/* stop the transmit queue so nothing more can be transmitted */
+	netif_stop_queue(netdev);
+
+	napi_disable(&devdata->napi);
+
 	skb_queue_purge(&devdata->xmitbufhead);
 
 	/* Free rcv buffers - other end has automatically unposed them on
@@ -692,6 +648,7 @@ visornic_enable_with_timeout(struct net_device *netdev, const int timeout)
 	/* send enable and wait for ack -- don't hold lock when sending enable
 	 * because if the queue is full, insert might sleep.
 	 */
+	napi_enable(&devdata->napi);
 	send_enbdis(netdev, 1, devdata);
 
 	spin_lock_irqsave(&devdata->priv_lock, flags);
@@ -719,6 +676,7 @@ visornic_enable_with_timeout(struct net_device *netdev, const int timeout)
 	}
 
 	netif_start_queue(netdev);
+
 	return 0;
 }
 
@@ -1198,15 +1156,16 @@ repost_return(struct uiscmdrsp *cmdrsp, struct visornic_devdata *devdata,
  *	it up the stack.
  *	Returns void
  */
-static void
+static int
 visornic_rx(struct uiscmdrsp *cmdrsp)
 {
 	struct visornic_devdata *devdata;
 	struct sk_buff *skb, *prev, *curr;
 	struct net_device *netdev;
-	int cc, currsize, off, status;
+	int cc, currsize, off;
 	struct ethhdr *eth;
 	unsigned long flags;
+	int rx_count = 0;
 
 	/* post new rcv buf to the other end using the cmdrsp we have at hand
 	 * post it without holding lock - but we'll use the signal lock to
@@ -1238,7 +1197,7 @@ visornic_rx(struct uiscmdrsp *cmdrsp)
 		 */
 		spin_unlock_irqrestore(&devdata->priv_lock, flags);
 		repost_return(cmdrsp, devdata, skb, netdev);
-		return;
+		return rx_count;
 	}
 
 	spin_unlock_irqrestore(&devdata->priv_lock, flags);
@@ -1257,7 +1216,7 @@ visornic_rx(struct uiscmdrsp *cmdrsp)
 			if (repost_return(cmdrsp, devdata, skb, netdev) < 0)
 				dev_err(&devdata->netdev->dev,
 					"repost_return failed");
-			return;
+			return rx_count;
 		}
 		/* length rcvd is greater than firstfrag in this skb rcv buf  */
 		skb->tail += RCVPOST_BUF_SIZE;	/* amount in skb->data */
@@ -1272,7 +1231,7 @@ visornic_rx(struct uiscmdrsp *cmdrsp)
 			if (repost_return(cmdrsp, devdata, skb, netdev) < 0)
 				dev_err(&devdata->netdev->dev,
 					"repost_return failed");
-			return;
+			return rx_count;
 		}
 		skb->tail += skb->len;
 		skb->data_len = 0;	/* nothing rcvd in frag_list */
@@ -1291,7 +1250,7 @@ visornic_rx(struct uiscmdrsp *cmdrsp)
 	if (cmdrsp->net.rcv.rcvbuf[0] != skb) {
 		if (repost_return(cmdrsp, devdata, skb, netdev) < 0)
 			dev_err(&devdata->netdev->dev, "repost_return failed");
-		return;
+		return rx_count;
 	}
 
 	if (cmdrsp->net.rcv.numrcvbufs > 1) {
@@ -1374,10 +1333,11 @@ visornic_rx(struct uiscmdrsp *cmdrsp)
 		/* drop packet - don't forward it up to OS */
 		devdata->n_rcv_packets_not_accepted++;
 		repost_return(cmdrsp, devdata, skb, netdev);
-		return;
+		return rx_count;
 	} while (0);
 
-	status = netif_rx(skb);
+	rx_count++;
+	netif_receive_skb(skb);
 	/* netif_rx returns various values, but "in practice most drivers
 	 * ignore the return value
 	 */
@@ -1389,6 +1349,7 @@ visornic_rx(struct uiscmdrsp *cmdrsp)
 	 * new rcv buffer.
 	 */
 	repost_return(cmdrsp, devdata, skb, netdev);
+	return rx_count;
 }
 
 /**
@@ -1593,9 +1554,6 @@ static ssize_t info_debugfs_read(struct file *file, char __user *buf,
 		str_pos += scnprintf(vbuf + str_pos, len - str_pos,
 				     " flow_control_lower_hits = %llu\n",
 				     devdata->flow_control_lower_hits);
-		str_pos += scnprintf(vbuf + str_pos, len - str_pos,
-				     " thread_wait_ms = %d\n",
-				     devdata->thread_wait_ms);
 		str_pos += scnprintf(vbuf + str_pos, len - str_pos,
 				     " netif_queue = %s\n",
 				     netif_queue_stopped(devdata->netdev) ?
@@ -1663,7 +1621,8 @@ send_rcv_posts_if_needed(struct visornic_devdata *devdata)
  *	Returns when response queue is empty or when the threadd stops.
  */
 static void
-drain_queue(struct uiscmdrsp *cmdrsp, struct visornic_devdata *devdata)
+service_resp_queue(struct uiscmdrsp *cmdrsp, struct visornic_devdata *devdata,
+		   int *rx_work_done)
 {
 	unsigned long flags;
 	struct net_device *netdev;
@@ -1680,7 +1639,7 @@ drain_queue(struct uiscmdrsp *cmdrsp, struct visornic_devdata *devdata)
 		case NET_RCV:
 			devdata->chstat.got_rcv++;
 			/* process incoming packet */
-			visornic_rx(cmdrsp);
+			*rx_work_done += visornic_rx(cmdrsp);
 			break;
 		case NET_XMIT_DONE:
 			spin_lock_irqsave(&devdata->priv_lock, flags);
@@ -1717,8 +1676,6 @@ drain_queue(struct uiscmdrsp *cmdrsp, struct visornic_devdata *devdata)
 			devdata->enab_dis_acked = 1;
 			spin_unlock_irqrestore(&devdata->priv_lock, flags);
 
-			if (kthread_should_stop())
-				break;
 			if (devdata->server_down &&
 			    devdata->server_change_state) {
 				/* Inform Linux that the link is up */
@@ -1753,42 +1710,48 @@ drain_queue(struct uiscmdrsp *cmdrsp, struct visornic_devdata *devdata)
 	}
 }
 
+static int visornic_poll(struct napi_struct *napi, int budget)
+{
+	struct visornic_devdata *devdata = container_of(napi,
+							struct visornic_devdata,
+							napi);
+	int rx_count = 0;
+
+	send_rcv_posts_if_needed(devdata);
+	service_resp_queue(devdata->cmdrsp, devdata, &rx_count);
+
+	/*
+	 * If there aren't any more packets to receive
+	 * stop the poll
+	 */
+	if (rx_count < budget)
+		napi_complete(napi);
+
+	return rx_count;
+}
+
 /**
- *	process_incoming_rsps	- Checks the status of the response queue.
+ *	poll_for_irq	- Checks the status of the response queue.
  *	@v: void pointer to the visronic devdata
  *
  *	Main function of the vnic_incoming thread. Peridocially check the
  *	response queue and drain it if needed.
  *	Returns when thread has stopped.
  */
-static int
-process_incoming_rsps(void *v)
+static void
+poll_for_irq(unsigned long v)
 {
-	struct visornic_devdata *devdata = v;
-	struct uiscmdrsp *cmdrsp = NULL;
-	const int SZ = SIZEOF_CMDRSP;
+	struct visornic_devdata *devdata = (struct visornic_devdata *)v;
 
-	cmdrsp = kmalloc(SZ, GFP_ATOMIC);
-	if (!cmdrsp)
-		return 0;
+	if (!visorchannel_signalempty(
+				   devdata->dev->visorchannel,
+				   IOCHAN_FROM_IOPART))
+		napi_schedule(&devdata->napi);
 
-	while (!kthread_should_stop()) {
-		wait_event_interruptible_timeout(
-			devdata->rsp_queue, (atomic_read(
-					     &devdata->interrupt_rcvd) == 1),
-				msecs_to_jiffies(devdata->thread_wait_ms));
+	atomic_set(&devdata->interrupt_rcvd, 0);
 
-		/* periodically check to see if there are any rcf bufs which
-		 * need to get sent to the IOSP. This can only happen if
-		 * we run out of memory when trying to allocate skbs.
-		 */
-		atomic_set(&devdata->interrupt_rcvd, 0);
-		send_rcv_posts_if_needed(devdata);
-		drain_queue(cmdrsp, devdata);
-	}
+	mod_timer(&devdata->irq_poll_timer, msecs_to_jiffies(2));
 
-	kfree(cmdrsp);
-	return 0;
 }
 
 /**
@@ -1907,6 +1870,17 @@ static int visornic_probe(struct visor_device *dev)
 
 	/* TODO: Setup Interrupt information */
 	/* Let's start our threads to get responses */
+	netif_napi_add(netdev, &devdata->napi, visornic_poll, 64);
+
+	setup_timer(&devdata->irq_poll_timer, poll_for_irq,
+		    (unsigned long)devdata);
+	/*
+	 * Note: This time has to start running before the while
+	 * loop below because the napi routine is responsible for
+	 * setting enab_dis_acked
+	 */
+	mod_timer(&devdata->irq_poll_timer, msecs_to_jiffies(2));
+
 	channel_offset = offsetof(struct spar_io_channel_protocol,
 				  channel_header.features);
 	err = visorbus_read_channel(dev, channel_offset, &features, 8);
@@ -1914,7 +1888,7 @@ static int visornic_probe(struct visor_device *dev)
 		dev_err(&dev->device,
 			"%s failed to get features from chan (%d)\n",
 			__func__, err);
-		goto cleanup_xmit_cmdrsp;
+		goto cleanup_napi_add;
 	}
 
 	features |= ULTRA_IO_CHANNEL_IS_POLLING;
@@ -1923,14 +1897,14 @@ static int visornic_probe(struct visor_device *dev)
 		dev_err(&dev->device,
 			"%s failed to set features in chan (%d)\n",
 			__func__, err);
-		goto cleanup_xmit_cmdrsp;
+		goto cleanup_napi_add;
 	}
 
 	err = register_netdev(netdev);
 	if (err) {
 		dev_err(&dev->device,
 			"%s register_netdev failed (%d)\n", __func__, err);
-		goto cleanup_xmit_cmdrsp;
+		goto cleanup_napi_add;
 	}
 
 	/* create debgug/sysfs directories */
@@ -1944,14 +1918,14 @@ static int visornic_probe(struct visor_device *dev)
 		goto cleanup_xmit_cmdrsp;
 	}
 
-	devdata->thread_wait_ms = 2;
-	visor_thread_start(&devdata->threadinfo, process_incoming_rsps,
-			   devdata, "vnic_incoming");
-
 	dev_info(&dev->device, "%s success netdev=%s\n",
 		 __func__, netdev->name);
 	return 0;
 
+cleanup_napi_add:
+	del_timer_sync(&devdata->irq_poll_timer);
+	netif_napi_del(&devdata->napi);
+
 cleanup_xmit_cmdrsp:
 	kfree(devdata->xmit_cmdrsp);
 
@@ -2021,18 +1995,8 @@ static void visornic_remove(struct visor_device *dev)
 
 	unregister_netdev(netdev);  /* this will call visornic_close() */
 
-	/* this had to wait until last because visornic_close() /
-	 * visornic_disable_with_timeout() polls waiting for state that is
-	 * only updated by the thread
-	 */
-	if (devdata->threadinfo.id) {
-		visor_thread_stop(&devdata->threadinfo);
-		if (devdata->threadinfo.id) {
-			dev_err(&dev->device, "%s cannot stop worker thread\n",
-				__func__);
-			return;
-		}
-	}
+	del_timer_sync(&devdata->irq_poll_timer);
+	netif_napi_del(&devdata->napi);
 
 	dev_set_drvdata(&dev->device, NULL);
 	host_side_disappeared(devdata);
@@ -2102,16 +2066,14 @@ static int visornic_resume(struct visor_device *dev,
 	}
 	devdata->server_change_state = true;
 	spin_unlock_irqrestore(&devdata->priv_lock, flags);
+
 	/* Must transition channel to ATTACHED state BEFORE
 	 * we can start using the device again.
 	 * TODO: State transitions
 	 */
-	if (!devdata->threadinfo.id)
-		visor_thread_start(&devdata->threadinfo,
-				   process_incoming_rsps,
-				   devdata, "vnic_incoming");
-	else
-		pr_warn("vnic_incoming already running!\n");
+	mod_timer(&devdata->irq_poll_timer, msecs_to_jiffies(2));
+
+	init_rcv_bufs(netdev, devdata);
 
 	rtnl_lock();
 	dev_open(netdev);