aquantia: Setup max_mtu in ndev to enable jumbo frames

Although hardware is capable for almost 16K MTU, without max_mtu field
correctly set it only allows standard MTU to be used.
This patch enables max MTU, calculating it from hardware maximum frame size
of 16352 octets (including FCS).

Fixes: 5513e164 ("net: ethernet: aquantia: Fixes for aq_ndev_change_mtu")
Signed-off-by: Pavel Belous <Pavel.Belous@aquantia.com>
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/aquantia/atlantic/aq_nic.c

@@ -214,7 +214,6 @@ struct aq_nic_s *aq_nic_alloc_cold(const struct net_device_ops *ndev_ops,
 	SET_NETDEV_DEV(ndev, dev);
 
 	ndev->if_port = port;
-	ndev->min_mtu = ETH_MIN_MTU;
 	self->ndev = ndev;
 
 	self->aq_pci_func = aq_pci_func;
@@ -283,6 +282,7 @@ int aq_nic_ndev_init(struct aq_nic_s *self)
 	self->ndev->features = aq_hw_caps->hw_features;
 	self->ndev->priv_flags = aq_hw_caps->hw_priv_flags;
 	self->ndev->mtu = aq_nic_cfg->mtu - ETH_HLEN;
+	self->ndev->max_mtu = self->aq_hw_caps.mtu - ETH_FCS_LEN - ETH_HLEN;
 
 	return 0;
 }
@@ -693,16 +693,9 @@ int aq_nic_set_multicast_list(struct aq_nic_s *self, struct net_device *ndev)
 
 int aq_nic_set_mtu(struct aq_nic_s *self, int new_mtu)
 {
-	int err = 0;
-
-	if (new_mtu > self->aq_hw_caps.mtu) {
-		err = -EINVAL;
-		goto err_exit;
-	}
 	self->aq_nic_cfg.mtu = new_mtu;
 
-err_exit:
-	return err;
+	return 0;
 }
 
 int aq_nic_set_mac(struct aq_nic_s *self, struct net_device *ndev)

drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0_internal.h

@@ -16,7 +16,7 @@
 
 #include "../aq_common.h"
 
-#define HW_ATL_B0_MTU_JUMBO (16000U)
+#define HW_ATL_B0_MTU_JUMBO  16352U
 #define HW_ATL_B0_MTU        1514U
 
 #define HW_ATL_B0_TX_RINGS 4U