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net: lan966x: Fix FDMA when MTU is changed

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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>
This commit is contained in:
Horatiu Vultur 2022-10-30 22:36:36 +01:00 committed by Jakub Kicinski
parent 25f28bb1b4
commit 872ad758f9
2 changed files with 7 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
View File

@ -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)

2
drivers/net/ethernet/microchip/lan966x/lan966x_main.c
View File

@ -395,7 +395,7 @@ 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;
}