[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID:
<PAXPR04MB8510EA7CD915DE9340303B0F8807A@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Mon, 1 Sep 2025 06:52:32 +0000
From: Wei Fang <wei.fang@....com>
To: Shenwei Wang <shenwei.wang@....com>
CC: Clark Wang <xiaoning.wang@....com>, Stanislav Fomichev <sdf@...ichev.me>,
"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "netdev@...r.kernel.org"
<netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, dl-linux-imx <linux-imx@....com>, Andrew Lunn
<andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, Eric
Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
<daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, John
Fastabend <john.fastabend@...il.com>
Subject: RE: [PATCH v4 net-next 4/5] net: fec: add change_mtu to support
dynamic buffer allocation
> * 2048 byte skbufs are allocated. However, alignment requirements
> * varies between FEC variants. Worst case is 64, so round down by 64.
> */
> +#define FEC_DRV_RESERVE_SPACE \
> + (XDP_PACKET_HEADROOM + \
> + SKB_DATA_ALIGN((unsigned int)sizeof(struct skb_shared_info)))
"unsigned int" can be removed. And please move FEC_DRV_RESERVE_SPACE
to fec.h, FEC_ENET_RX_FRSIZE can be updated to
(PAGE_SIZE - FEC_DRV_RESERVE_SPACE).
> +static int fec_change_mtu(struct net_device *ndev, int new_mtu)
> +{
> + struct fec_enet_private *fep = netdev_priv(ndev);
> + int old_mtu, old_order, old_size, order, done;
> + int ret = 0;
> +
> + order = get_order(new_mtu + ETH_HLEN + ETH_FCS_LEN +
> FEC_DRV_RESERVE_SPACE);
> + old_order = fep->pagepool_order;
> + old_size = fep->rx_frame_size;
> + old_mtu = READ_ONCE(ndev->mtu);
> + fep->pagepool_order = order;
> + fep->rx_frame_size = (PAGE_SIZE << order) - FEC_DRV_RESERVE_SPACE;
> +
> + if (!netif_running(ndev)) {
> + WRITE_ONCE(ndev->mtu, new_mtu);
> + return 0;
> + }
> +
> + /* Stop TX/RX and free the buffers */
> + napi_disable(&fep->napi);
> + netif_tx_disable(ndev);
> + read_poll_timeout(fec_enet_rx_napi, done, (done == 0),
> + 10, 1000, false, &fep->napi, 10);
> + fec_stop(ndev);
> +
> + WRITE_ONCE(ndev->mtu, new_mtu);
> +
> + if (fep->pagepool_order != old_order) {
If fep->pagepool_order is not changed, why need to stop TX/RX?
> + fec_enet_free_buffers(ndev);
> +
> + /* Create the pagepool based on the new mtu.
> + * Revert to the original settings if buffer
> + * allocation fails.
> + */
> + if (fec_enet_alloc_buffers(ndev) < 0) {
> + fep->pagepool_order = old_order;
> + fep->rx_frame_size = old_size;
> + WRITE_ONCE(ndev->mtu, old_mtu);
> + fec_enet_alloc_buffers(ndev);
fec_enet_alloc_buffers() may still fail here, the best approach is to add a helper
function that allocates new buffers before freeing the old ones. However, this is
a complex change, so I think returning an error is sufficient for now, and we can
consider improving it later.
Powered by blists - more mailing lists