[PATCH net-next v9 17/17] net: macb: use context swapping in .ndo_change_mtu()
From: Théo Lebrun <theo.lebrun@bootlin.com>
Date: 2026-08-12 08:04:26
Also in:
lkml
Subsystem:
atmel macb ethernet driver, networking drivers, the rest · Maintainers:
Théo Lebrun, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Use newly introduced context buffer management to implement .ndo_change_mtu() as a context swap: allocate new context -> reconfigure HW -> free old context. This resists memory pressure well by failing without closing the interface and it is much faster by avoiding PHY reinit. AT91 EMAC is handled differently as their buffer management is separate and they don't do NAPI. They cannot land in macb_change_mtu as they use a different ndo struct. We still defensively protect against it in code. Reviewed-by: Nicolai Buchwitz <redacted> Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com> --- drivers/net/ethernet/cadence/macb_main.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 55c97f2035e7..3160e815a89a 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c@@ -3530,11 +3530,29 @@ static int macb_close(struct net_device *netdev) static int macb_change_mtu(struct net_device *netdev, int new_mtu) { - if (netif_running(netdev)) - return -EBUSY; + struct macb *bp = netdev_priv(netdev); + bool running = netif_running(netdev); + struct macb_context *new_ctx; + + if (running) { + /* Context swapping is not supported for AT91. */ + if (bp->caps & MACB_CAPS_MACB_IS_EMAC) + return -EBUSY; + + new_ctx = macb_context_alloc(bp, new_mtu, + bp->configured_rx_ring_size, + bp->configured_tx_ring_size); + if (IS_ERR(new_ctx)) + return PTR_ERR(new_ctx); + + macb_context_swap_start(bp); + } WRITE_ONCE(netdev->mtu, new_mtu); + if (running) + macb_context_swap_end(bp, new_ctx); + return 0; }
--
2.55.0