[PATCH 4.4 7/9] net/ncsi: Fix stale link state of inactive channels on failover

[Gavin Shan]

The issue was found on BCM5718 which has two NCSI channels in one
package: C0 and C1. Both of them are connected to different LANs,
means they are in link-up state and C0 is chosen as the active one
until resetting BCM5718 happens as below.

Resetting BCM5718 results in LSC (Link State Change) AEN packet
received on C0, meaning LSC AEN is missed on C1. When LSC AEN packet
received on C0 to report link-down, it fails over to C1 because C1
is in link-up state as software can see. However, C1 is in link-down
state in hardware. It means the link state is out of synchronization
between hardware and software, resulting in inappropriate channel (C1)
selected as active one.

This resolves the issue by sending separate GLS (Get Link Status)
commands to all channels in the package before trying to do failover.
The last link states of all channels in the package are retrieved.
With it, C0 (not C1) is selected as active one as expected.

Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
---
 net/ncsi/internal.h    |  1 +
 net/ncsi/ncsi-manage.c | 29 ++++++++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/net/ncsi/internal.h b/net/ncsi/internal.h
index 18a477b..1696b1b 100644
--- a/net/ncsi/internal.h
+++ b/net/ncsi/internal.h
@@ -71,6 +71,7 @@ enum {
 	ncsi_dev_state_config_gls,
 	ncsi_dev_state_config_done,
 	ncsi_dev_state_suspend_select	= 0x0401,
+	ncsi_dev_state_suspend_gls,
 	ncsi_dev_state_suspend_dcnt,
 	ncsi_dev_state_suspend_dc,
 	ncsi_dev_state_suspend_deselect,
diff --git a/net/ncsi/ncsi-manage.c b/net/ncsi/ncsi-manage.c
index 99045ed..a3bae7b 100644
--- a/net/ncsi/ncsi-manage.c
+++ b/net/ncsi/ncsi-manage.c
@@ -718,12 +718,39 @@ static void ncsi_dev_suspend(struct ncsi_dev_priv *ndp)
 		nca.nca_channel = NCSI_RESERVED_CHANNEL;
 		nca.nca_bytes[0] = 1;
 
-		nd->nd_state = ncsi_dev_state_suspend_dcnt;
+		/* To retrieve the last link states of channels in current
+		 * package when current active channel needs fail over to
+		 * another one. It means we will possibly select another
+		 * channel as next active one. The link states of channels
+		 * are most important factor of the selection. So we need
+		 * accurate link states. Unfortunately, the link states on
+		 * inactive channels can't be updated with LSC AEN in time.
+		 */
+		if (ndp->ndp_flags & NCSI_DEV_PRIV_FLAG_CHANGE_ACTIVE)
+			nd->nd_state = ncsi_dev_state_suspend_gls;
+		else
+			nd->nd_state = ncsi_dev_state_suspend_dcnt;
 		ret = ncsi_xmit_cmd(&nca);
 		if (ret)
 			goto error;
 
 		break;
+	case ncsi_dev_state_suspend_gls:
+		atomic_set(&ndp->ndp_pending_reqs,
+			   atomic_read(&np->np_channel_num));
+
+		nca.nca_type = NCSI_PKT_CMD_GLS;
+		nca.nca_package = np->np_id;
+
+		nd->nd_state = ncsi_dev_state_suspend_dcnt;
+		NCSI_FOR_EACH_CHANNEL(np, nc) {
+			nca.nca_channel = nc->nc_id;
+			ret = ncsi_xmit_cmd(&nca);
+			if (ret)
+				goto error;
+		}
+
+		break;
 	case ncsi_dev_state_suspend_dcnt:
 		atomic_set(&ndp->ndp_pending_reqs, 1);
 
-- 
2.1.0