net: ethernet: ti: am65-cpsw: fix tx csum offload for multi mac mode

The current implementation uses .ndo_set_features() callback to track
NETIF_F_HW_CSUM feature changes and update generic
CPSW_P0_CONTROL_REG.RX_CHECKSUM_EN option accordingly. It's not going to
work in case of multi-port devices as TX csum offload can be changed per
netdev.

On K3 CPSWxG devices TX csum offload enabled in the following way:

 - the CPSW_P0_CONTROL_REG.RX_CHECKSUM_EN option enables TX csum offload in
generic and affects all TX DMA channels and packets;

 - corresponding fields in TX DMA descriptor have to be filed properly when
upper layer wants to offload TX csum (skb->ip_summed == CHECKSUM_PARTIAL)
and it's per-packet option.

The Linux Network core is expected to never request TX csum offload if
netdev NETIF_F_HW_CSUM feature is disabled, and, as result, TX DMA
descriptors should not be modified, and per-packet TX csum offload will be
disabled (or enabled) on per-netdev basis. Which, in turn, makes it safe to
enable the CPSW_P0_CONTROL_REG.RX_CHECKSUM_EN option unconditionally.

Hence, fix TX csum offload for multi-port devices by:
 - enabling the CPSW_P0_CONTROL_REG.RX_CHECKSUM_EN option in
am65_cpsw_nuss_common_open() unconditionally
 - and removing .ndo_set_features() callback implementation, which was used
only NETIF_F_HW_CSUM feature update purposes

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/ti/am65-cpsw-nuss.c

@@ -428,9 +428,7 @@ static int am65_cpsw_nuss_common_open(struct am65_cpsw_common *common,
 	writel(common->rx_flow_id_base,
 	       host_p->port_base + AM65_CPSW_PORT0_REG_FLOW_ID_OFFSET);
 	/* en tx crc offload */
-	if (features & NETIF_F_HW_CSUM)
-		writel(AM65_CPSW_P0_REG_CTL_RX_CHECKSUM_EN,
-		       host_p->port_base + AM65_CPSW_P0_REG_CTL);
+	writel(AM65_CPSW_P0_REG_CTL_RX_CHECKSUM_EN, host_p->port_base + AM65_CPSW_P0_REG_CTL);
 
 	am65_cpsw_nuss_set_p0_ptype(common);
 
@@ -1371,31 +1369,6 @@ static void am65_cpsw_nuss_ndo_get_stats(struct net_device *dev,
 	stats->tx_dropped	= dev->stats.tx_dropped;
 }
 
-static int am65_cpsw_nuss_ndo_slave_set_features(struct net_device *ndev,
-						 netdev_features_t features)
-{
-	struct am65_cpsw_common *common = am65_ndev_to_common(ndev);
-	netdev_features_t changes = features ^ ndev->features;
-	struct am65_cpsw_host *host_p;
-
-	host_p = am65_common_get_host(common);
-
-	if (changes & NETIF_F_HW_CSUM) {
-		bool enable = !!(features & NETIF_F_HW_CSUM);
-
-		dev_info(common->dev, "Turn %s tx-checksum-ip-generic\n",
-			 enable ? "ON" : "OFF");
-		if (enable)
-			writel(AM65_CPSW_P0_REG_CTL_RX_CHECKSUM_EN,
-			       host_p->port_base + AM65_CPSW_P0_REG_CTL);
-		else
-			writel(0,
-			       host_p->port_base + AM65_CPSW_P0_REG_CTL);
-	}
-
-	return 0;
-}
-
 static const struct net_device_ops am65_cpsw_nuss_netdev_ops_2g = {
 	.ndo_open		= am65_cpsw_nuss_ndo_slave_open,
 	.ndo_stop		= am65_cpsw_nuss_ndo_slave_stop,
@@ -1408,7 +1381,6 @@ static const struct net_device_ops am65_cpsw_nuss_netdev_ops_2g = {
 	.ndo_vlan_rx_add_vid	= am65_cpsw_nuss_ndo_slave_add_vid,
 	.ndo_vlan_rx_kill_vid	= am65_cpsw_nuss_ndo_slave_kill_vid,
 	.ndo_do_ioctl		= am65_cpsw_nuss_ndo_slave_ioctl,
-	.ndo_set_features	= am65_cpsw_nuss_ndo_slave_set_features,
 	.ndo_setup_tc           = am65_cpsw_qos_ndo_setup_tc,
 };