ixgbe: DCB: enable RSS to be used with DCB

RSS had previously been disabled when DCB was enabled because
DCB was single queued per traffic class. Now that DCB implements
multiple Tx/Rx rings per traffic class enable RSS.

Here RSS hashes across the queues in the traffic class.

Signed-off-by: John Fastabend <[e-mail]>
Tested-by: Ross Brattain <[e-mail]>
Signed-off-by: Jeff Kirsher <[e-mail]>

drivers/net/ixgbe/ixgbe_dcb_nl.c

···
 			netdev->netdev_ops->ndo_stop(netdev);
 		ixgbe_clear_interrupt_scheme(adapter);
 
-		adapter->flags &= ~IXGBE_FLAG_RSS_ENABLED;
 		switch (adapter->hw.mac.type) {
 		case ixgbe_mac_82598EB:
 			adapter->last_lfc_mode = adapter->hw.fc.current_mode;
···
 			adapter->temp_dcb_cfg.pfc_mode_enable = false;
 			adapter->dcb_cfg.pfc_mode_enable = false;
 			adapter->flags &= ~IXGBE_FLAG_DCB_ENABLED;
-			adapter->flags |= IXGBE_FLAG_RSS_ENABLED;
 			switch (adapter->hw.mac.type) {
 			case ixgbe_mac_82599EB:
 			case ixgbe_mac_X540:

drivers/net/ixgbe/ixgbe_main.c

···
 					);
 
 	switch (mask) {
+#ifdef CONFIG_IXGBE_DCB
+	case (IXGBE_FLAG_DCB_ENABLED | IXGBE_FLAG_RSS_ENABLED):
+		mrqc = IXGBE_MRQC_RTRSS8TCEN;
+		break;
+	case (IXGBE_FLAG_DCB_ENABLED):
+		mrqc = IXGBE_MRQC_RT8TCEN;
+		break;
+#endif /* CONFIG_IXGBE_DCB */
 	case (IXGBE_FLAG_RSS_ENABLED):
 		mrqc = IXGBE_MRQC_RSSEN;
 		break;
 	case (IXGBE_FLAG_SRIOV_ENABLED):
 		mrqc = IXGBE_MRQC_VMDQEN;
 		break;
-#ifdef CONFIG_IXGBE_DCB
-	case (IXGBE_FLAG_DCB_ENABLED):
-		mrqc = IXGBE_MRQC_RT8TCEN;
-		break;
-#endif /* CONFIG_IXGBE_DCB */
 	default:
 		break;
 	}
···
 
 	/* reconfigure the hardware */
 	ixgbe_dcb_hw_config(hw, &adapter->dcb_cfg);
+
+	/* Enable RSS Hash per TC */
+	if (hw->mac.type != ixgbe_mac_82598EB) {
+		int i;
+		u32 reg = 0;
+
+		for (i = 0; i < MAX_TRAFFIC_CLASS; i++) {
+			u8 msb = 0;
+			u8 cnt = adapter->netdev->tc_to_txq[i].count;
+
+			while (cnt >>= 1)
+				msb++;
+
+			reg |= msb << IXGBE_RQTC_SHIFT_TC(i);
+		}
+		IXGBE_WRITE_REG(hw, IXGBE_RQTC, reg);
+	}
 }
 
 #endif
···
 	if (adapter->flags & IXGBE_FLAG_SRIOV_ENABLED)
 		adapter->flags &= ~(IXGBE_FLAG_RSS_ENABLED |
 				    IXGBE_FLAG_DCB_ENABLED);
-	if (adapter->flags & IXGBE_FLAG_DCB_ENABLED)
-		adapter->flags &= ~IXGBE_FLAG_RSS_ENABLED;
 
 #ifdef CONFIG_IXGBE_DCB
 	netdev->dcbnl_ops = &dcbnl_ops;