net: thunderx: Fix OOPs with ethtool --register-dump

BugLink: http://bugs.launchpad.net/bugs/1627730

commit 1423661f upstream.

The ethtool_ops .get_regs function attempts to read the nonexistent
register NIC_QSET_SQ_0_7_CNM_CHG, which produces a "bus error" type
OOPs.

Fix by not attempting to read, and removing the definition of,
NIC_QSET_SQ_0_7_CNM_CHG.  A zero is written into the register dump to
keep the layout unchanged.
Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/net/ethernet/cavium/thunder/nic_reg.h

@@ -170,7 +170,6 @@
 #define   NIC_QSET_SQ_0_7_DOOR			(0x010838)
 #define   NIC_QSET_SQ_0_7_STATUS		(0x010840)
 #define   NIC_QSET_SQ_0_7_DEBUG			(0x010848)
-#define   NIC_QSET_SQ_0_7_CNM_CHG		(0x010860)
 #define   NIC_QSET_SQ_0_7_STAT_0_1		(0x010900)
 
 #define   NIC_QSET_RBDR_0_1_CFG			(0x010C00)

drivers/net/ethernet/cavium/thunder/nicvf_ethtool.c

@@ -382,7 +382,10 @@ static void nicvf_get_regs(struct net_device *dev,
 		p[i++] = nicvf_queue_reg_read(nic, NIC_QSET_SQ_0_7_DOOR, q);
 		p[i++] = nicvf_queue_reg_read(nic, NIC_QSET_SQ_0_7_STATUS, q);
 		p[i++] = nicvf_queue_reg_read(nic, NIC_QSET_SQ_0_7_DEBUG, q);
-		p[i++] = nicvf_queue_reg_read(nic, NIC_QSET_SQ_0_7_CNM_CHG, q);
+		/* Padding, was NIC_QSET_SQ_0_7_CNM_CHG, which
+		 * produces bus errors when read
+		 */
+		p[i++] = 0;
 		p[i++] = nicvf_queue_reg_read(nic, NIC_QSET_SQ_0_7_STAT_0_1, q);
 		reg_offset = NIC_QSET_SQ_0_7_STAT_0_1 | (1 << 3);
 		p[i++] = nicvf_queue_reg_read(nic, reg_offset, q);