net: lan966x: Fix FDMA when MTU is changed

[ Upstream commit 872ad758f9b7fb4eb42aebaf64e50c5b29b7ffe5 ]

When MTU is changed, FDMA is required to calculate what is the maximum
size of the frame that it can received. So it can calculate what is the
page order needed to allocate for the received frames.
The first problem was that, when the max MTU was calculated it was
reading the value from dev and not from HW, so in this way it was
missing L2 header + the FCS.
The other problem was that once the skb is created using
__build_skb_around, it would reserve some space for skb_shared_info.
So if we received a frame which size is at the limit of the page order
then the creating will failed because it would not have space to put all
the data.

Fixes: 2ea1cbac267e ("net: lan966x: Update FDMA to change MTU.")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
index 69f741db25b1f32c64d39cba74df2d668e512643..407a6c125515357a5098ae65555427cff8248a2d 100644 (file)
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
@@ -668,12 +668,14 @@ static int lan966x_fdma_get_max_mtu(struct lan966x *lan966x)
        int i;
 
        for (i = 0; i < lan966x->num_phys_ports; ++i) {
+               struct lan966x_port *port;
                int mtu;
 
-               if (!lan966x->ports[i])
+               port = lan966x->ports[i];
+               if (!port)
                        continue;
 
-               mtu = lan966x->ports[i]->dev->mtu;
+               mtu = lan_rd(lan966x, DEV_MAC_MAXLEN_CFG(port->chip_port));
                if (mtu > max_mtu)
                        max_mtu = mtu;
        }
@@ -733,6 +735,8 @@ int lan966x_fdma_change_mtu(struct lan966x *lan966x)
 
        max_mtu = lan966x_fdma_get_max_mtu(lan966x);
        max_mtu += IFH_LEN * sizeof(u32);
+       max_mtu += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+       max_mtu += VLAN_HLEN * 2;
 
        if (round_up(max_mtu, PAGE_SIZE) / PAGE_SIZE - 1 ==
            lan966x->rx.page_order)

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
index 989e5f045d7ec06328cdf2555653db14665cc96c..4a3cb7579420223b4347bb3be887fd161e8363e6 100644 (file)
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
@@ -394,7 +394,7 @@ static int lan966x_port_change_mtu(struct net_device *dev, int new_mtu)
 
        err = lan966x_fdma_change_mtu(lan966x);
        if (err) {
-               lan_wr(DEV_MAC_MAXLEN_CFG_MAX_LEN_SET(old_mtu),
+               lan_wr(DEV_MAC_MAXLEN_CFG_MAX_LEN_SET(LAN966X_HW_MTU(old_mtu)),
                       lan966x, DEV_MAC_MAXLEN_CFG(port->chip_port));
                dev->mtu = old_mtu;
        }