net/ncsi: Rework the channel monitoring

The original NCSI channel monitoring was implemented based on a
backoff algorithm: the GLS response should be received in the
specified interval. Otherwise, the channel is regarded as dead
and failover should be taken if current channel is an active one.
There are several problems in the implementation: (A) On BCM5718,
we found when the IID (Instance ID) in the GLS command packet
changes from 255 to 1, the response corresponding to IID#1 never
comes in. It means we cannot make the unfair judgement that the
channel is dead when one response is missed. (B) The code's
readability should be improved. (C) We should do failover when
current channel is active one and the channel monitoring should
be marked as disabled before doing failover.

This reworks the channel monitoring to address all above issues.
The fields for channel monitoring is put into separate struct
and the state of channel monitoring is predefined. The channel
is regarded alive if the network controller responses to one of
two GLS commands or both of them in 5 seconds.
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ncsi/internal.h

@@ -187,9 +187,15 @@ struct ncsi_channel {
 	struct ncsi_channel_mode    modes[NCSI_MODE_MAX];
 	struct ncsi_channel_filter  *filters[NCSI_FILTER_MAX];
 	struct ncsi_channel_stats   stats;
-	struct timer_list           timer;	/* Link monitor timer  */
-	bool                        enabled;	/* Timer is enabled    */
-	unsigned int                timeout;	/* Times of timeout    */
+	struct {
+		struct timer_list   timer;
+		bool                enabled;
+		unsigned int        state;
+#define NCSI_CHANNEL_MONITOR_START	0
+#define NCSI_CHANNEL_MONITOR_RETRY	1
+#define NCSI_CHANNEL_MONITOR_WAIT	2
+#define NCSI_CHANNEL_MONITOR_WAIT_MAX	5
+	} monitor;
 	struct list_head            node;
 	struct list_head            link;
 };

net/ncsi/ncsi-manage.c

@@ -172,15 +172,15 @@ static void ncsi_channel_monitor(unsigned long data)
 	struct ncsi_dev_priv *ndp = np->ndp;
 	struct ncsi_cmd_arg nca;
 	bool enabled, chained;
-	unsigned int timeout;
+	unsigned int monitor_state;
 	unsigned long flags;
 	int state, ret;
 
 	spin_lock_irqsave(&nc->lock, flags);
 	state = nc->state;
 	chained = !list_empty(&nc->link);
-	timeout = nc->timeout;
-	enabled = nc->enabled;
+	enabled = nc->monitor.enabled;
+	monitor_state = nc->monitor.state;
 	spin_unlock_irqrestore(&nc->lock, flags);
 
 	if (!enabled || chained)
@@ -189,7 +189,9 @@ static void ncsi_channel_monitor(unsigned long data)
 	    state != NCSI_CHANNEL_ACTIVE)
 		return;
 
-	if (!(timeout % 2)) {
+	switch (monitor_state) {
+	case NCSI_CHANNEL_MONITOR_START:
+	case NCSI_CHANNEL_MONITOR_RETRY:
 		nca.ndp = ndp;
 		nca.package = np->id;
 		nca.channel = nc->id;
@@ -201,12 +203,16 @@ static void ncsi_channel_monitor(unsigned long data)
 				   ret);
 			return;
 		}
-	}
 
-	if (timeout + 1 >= 3) {
+		break;
+	case NCSI_CHANNEL_MONITOR_WAIT ... NCSI_CHANNEL_MONITOR_WAIT_MAX:
+		break;
+	default:
 		if (!(ndp->flags & NCSI_DEV_HWA) &&
-		    state == NCSI_CHANNEL_ACTIVE)
+		    state == NCSI_CHANNEL_ACTIVE) {
 			ncsi_report_link(ndp, true);
+			ndp->flags |= NCSI_DEV_RESHUFFLE;
+		}
 
 		spin_lock_irqsave(&nc->lock, flags);
 		nc->state = NCSI_CHANNEL_INVISIBLE;
@@ -221,10 +227,9 @@ static void ncsi_channel_monitor(unsigned long data)
 	}
 
 	spin_lock_irqsave(&nc->lock, flags);
-	nc->timeout = timeout + 1;
-	nc->enabled = true;
+	nc->monitor.state++;
 	spin_unlock_irqrestore(&nc->lock, flags);
-	mod_timer(&nc->timer, jiffies + HZ * (1 << (nc->timeout / 2)));
+	mod_timer(&nc->monitor.timer, jiffies + HZ);
 }
 
 void ncsi_start_channel_monitor(struct ncsi_channel *nc)
@@ -232,12 +237,12 @@ void ncsi_start_channel_monitor(struct ncsi_channel *nc)
 	unsigned long flags;
 
 	spin_lock_irqsave(&nc->lock, flags);
-	WARN_ON_ONCE(nc->enabled);
-	nc->timeout = 0;
-	nc->enabled = true;
+	WARN_ON_ONCE(nc->monitor.enabled);
+	nc->monitor.enabled = true;
+	nc->monitor.state = NCSI_CHANNEL_MONITOR_START;
 	spin_unlock_irqrestore(&nc->lock, flags);
 
-	mod_timer(&nc->timer, jiffies + HZ * (1 << (nc->timeout / 2)));
+	mod_timer(&nc->monitor.timer, jiffies + HZ);
 }
 
 void ncsi_stop_channel_monitor(struct ncsi_channel *nc)
@@ -245,14 +250,14 @@ void ncsi_stop_channel_monitor(struct ncsi_channel *nc)
 	unsigned long flags;
 
 	spin_lock_irqsave(&nc->lock, flags);
-	if (!nc->enabled) {
+	if (!nc->monitor.enabled) {
 		spin_unlock_irqrestore(&nc->lock, flags);
 		return;
 	}
-	nc->enabled = false;
+	nc->monitor.enabled = false;
 	spin_unlock_irqrestore(&nc->lock, flags);
 
-	del_timer_sync(&nc->timer);
+	del_timer_sync(&nc->monitor.timer);
 }
 
 struct ncsi_channel *ncsi_find_channel(struct ncsi_package *np,
@@ -281,8 +286,9 @@ struct ncsi_channel *ncsi_add_channel(struct ncsi_package *np, unsigned char id)
 	nc->id = id;
 	nc->package = np;
 	nc->state = NCSI_CHANNEL_INACTIVE;
-	nc->enabled = false;
-	setup_timer(&nc->timer, ncsi_channel_monitor, (unsigned long)nc);
+	nc->monitor.enabled = false;
+	setup_timer(&nc->monitor.timer,
+		    ncsi_channel_monitor, (unsigned long)nc);
 	spin_lock_init(&nc->lock);
 	INIT_LIST_HEAD(&nc->link);
 	for (index = 0; index < NCSI_CAP_MAX; index++)

net/ncsi/ncsi-rsp.c

@@ -322,7 +322,7 @@ static int ncsi_rsp_handler_gls(struct ncsi_request *nr)
 
 	/* Reset the channel monitor if it has been enabled */
 	spin_lock_irqsave(&nc->lock, flags);
-	nc->timeout = 0;
+	nc->monitor.state = NCSI_CHANNEL_MONITOR_START;
 	spin_unlock_irqrestore(&nc->lock, flags);
 
 	return 0;