[PATCH net 3/5] net/ncsi: Fix stale link state of inactive channels on failover

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

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 state on all channels in the package is retrieved. With
it, C0 is selected as active one as expected.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
---
 net/ncsi/internal.h    |  1 +
 net/ncsi/ncsi-manage.c | 20 +++++++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/net/ncsi/internal.h b/net/ncsi/internal.h
index 13290a7..eac4858 100644
--- a/net/ncsi/internal.h
+++ b/net/ncsi/internal.h
@@ -246,6 +246,7 @@ 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 5758a26..e959979 100644
--- a/net/ncsi/ncsi-manage.c
+++ b/net/ncsi/ncsi-manage.c
@@ -550,13 +550,31 @@ static void ncsi_suspend_channel(struct ncsi_dev_priv *ndp)
 		else
 			nca.bytes[0] = 1;
 
-		nd->state = ncsi_dev_state_suspend_dcnt;
+		if (ndp->flags & NCSI_DEV_RESHUFFLE)
+			nd->state = ncsi_dev_state_suspend_gls;
+		else
+			nd->state = ncsi_dev_state_suspend_dcnt;
 
 		ret = ncsi_xmit_cmd(&nca);
 		if (ret)
 			goto error;
 
 		break;
+	case ncsi_dev_state_suspend_gls:
+		ndp->pending_req_num = np->channel_num;
+
+		nca.type = NCSI_PKT_CMD_GLS;
+		nca.package = np->id;
+		nd->state = ncsi_dev_state_suspend_dcnt;
+
+		NCSI_FOR_EACH_CHANNEL(np, nc) {
+			nca.channel = nc->id;
+			ret = ncsi_xmit_cmd(&nca);
+			if (ret)
+				goto error;
+		}
+
+		break;
 	case ncsi_dev_state_suspend_dcnt:
 	case ncsi_dev_state_suspend_dc:
 	case ncsi_dev_state_suspend_deselect:
-- 
2.1.0