[PATCH net-next 11/11] net: macb: use context swapping in .ndo_change_mtu()

Théo Lebrun
2026-04-01T16:39:53Z

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.

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
drivers/net/ethernet/cadence/macb_main.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 543356554c11..e10791bf1f4d 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -3438,11 +3438,25 @@ 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) {
+ 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;
}

--
2.53.0