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Date:   Tue,  9 Oct 2018 14:58:14 +1100
From:   Samuel Mendoza-Jonas <sam@...dozajonas.com>
To:     netdev@...r.kernel.org
Cc:     Samuel Mendoza-Jonas <sam@...dozajonas.com>,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, openbmc@...ts.ozlabs.org,
        Justin.Lee1@...l.com
Subject: [RFC PATCH 1/2] net/ncsi: Don't enable all channels when HWA available

NCSI hardware arbitration allows multiple packages to be enabled at once
and share the same wiring. If the NCSI driver recognises that HWA is
available it unconditionally enables all packages and channels; but that
is a configuration decision rather than something required by HWA.
Additionally the current implementation will not failover on link events
which can cause connectivity to be lost unless the interface is manually
bounced.

Retain basic HWA support but remove the separate configuration path to
enable all channels, leaving this to be handled by a later
implementation.

Signed-off-by: Samuel Mendoza-Jonas <sam@...dozajonas.com>
---
 net/ncsi/ncsi-aen.c    |  3 +--
 net/ncsi/ncsi-manage.c | 51 +++++++-----------------------------------
 2 files changed, 9 insertions(+), 45 deletions(-)

diff --git a/net/ncsi/ncsi-aen.c b/net/ncsi/ncsi-aen.c
index 25e483e8278b..65f47a648be3 100644
--- a/net/ncsi/ncsi-aen.c
+++ b/net/ncsi/ncsi-aen.c
@@ -86,8 +86,7 @@ static int ncsi_aen_handler_lsc(struct ncsi_dev_priv *ndp,
 	    !(state == NCSI_CHANNEL_ACTIVE && !(data & 0x1)))
 		return 0;
 
-	if (!(ndp->flags & NCSI_DEV_HWA) &&
-	    state == NCSI_CHANNEL_ACTIVE)
+	if (state == NCSI_CHANNEL_ACTIVE)
 		ndp->flags |= NCSI_DEV_RESHUFFLE;
 
 	ncsi_stop_channel_monitor(nc);
diff --git a/net/ncsi/ncsi-manage.c b/net/ncsi/ncsi-manage.c
index 091284760d21..665bee25ec44 100644
--- a/net/ncsi/ncsi-manage.c
+++ b/net/ncsi/ncsi-manage.c
@@ -112,10 +112,8 @@ static void ncsi_channel_monitor(struct timer_list *t)
 	default:
 		netdev_err(ndp->ndev.dev, "NCSI Channel %d timed out!\n",
 			   nc->id);
-		if (!(ndp->flags & NCSI_DEV_HWA)) {
-			ncsi_report_link(ndp, true);
-			ndp->flags |= NCSI_DEV_RESHUFFLE;
-		}
+		ncsi_report_link(ndp, true);
+		ndp->flags |= NCSI_DEV_RESHUFFLE;
 
 		ncsi_stop_channel_monitor(nc);
 
@@ -952,35 +950,6 @@ static bool ncsi_check_hwa(struct ncsi_dev_priv *ndp)
 	return false;
 }
 
-static int ncsi_enable_hwa(struct ncsi_dev_priv *ndp)
-{
-	struct ncsi_package *np;
-	struct ncsi_channel *nc;
-	unsigned long flags;
-
-	/* Move all available channels to processing queue */
-	spin_lock_irqsave(&ndp->lock, flags);
-	NCSI_FOR_EACH_PACKAGE(ndp, np) {
-		NCSI_FOR_EACH_CHANNEL(np, nc) {
-			WARN_ON_ONCE(nc->state != NCSI_CHANNEL_INACTIVE ||
-				     !list_empty(&nc->link));
-			ncsi_stop_channel_monitor(nc);
-			list_add_tail_rcu(&nc->link, &ndp->channel_queue);
-		}
-	}
-	spin_unlock_irqrestore(&ndp->lock, flags);
-
-	/* We can have no channels in extremely case */
-	if (list_empty(&ndp->channel_queue)) {
-		netdev_err(ndp->ndev.dev,
-			   "NCSI: No available channels for HWA\n");
-		ncsi_report_link(ndp, false);
-		return -ENOENT;
-	}
-
-	return ncsi_process_next_channel(ndp);
-}
-
 static void ncsi_probe_channel(struct ncsi_dev_priv *ndp)
 {
 	struct ncsi_dev *nd = &ndp->ndev;
@@ -1047,6 +1016,10 @@ static void ncsi_probe_channel(struct ncsi_dev_priv *ndp)
 			ndp->active_package = list_next_entry(
 				ndp->active_package, node);
 
+		/* Check for HWA support */
+		if (ncsi_check_hwa(ndp))
+			netdev_info(ndp->ndev.dev, "NCSI: HWA available\n");
+
 		/* All available packages and channels are enumerated. The
 		 * enumeration happens for once when the NCSI interface is
 		 * started. So we need continue to start the interface after
@@ -1058,10 +1031,7 @@ static void ncsi_probe_channel(struct ncsi_dev_priv *ndp)
 		 */
 		if (!ndp->active_package) {
 			ndp->flags |= NCSI_DEV_PROBED;
-			if (ncsi_check_hwa(ndp))
-				ncsi_enable_hwa(ndp);
-			else
-				ncsi_choose_active_channel(ndp);
+			ncsi_choose_active_channel(ndp);
 			return;
 		}
 
@@ -1506,12 +1476,7 @@ int ncsi_start_dev(struct ncsi_dev *nd)
 		return 0;
 	}
 
-	if (ndp->flags & NCSI_DEV_HWA) {
-		netdev_info(ndp->ndev.dev, "NCSI: Enabling HWA mode\n");
-		ret = ncsi_enable_hwa(ndp);
-	} else {
-		ret = ncsi_choose_active_channel(ndp);
-	}
+	ret = ncsi_choose_active_channel(ndp);
 
 	return ret;
 }
-- 
2.19.0

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