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net: fec: enable the Jumbo frame support for i.MX8QM

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Certain i.MX SoCs, such as i.MX8QM and i.MX8QXP, feature enhanced
FEC hardware that supports Ethernet Jumbo frames with packet sizes
up to 16K bytes.

When Jumbo frames are supported, the TX FIFO may not be large enough
to hold an entire frame. To handle this, the FIFO is configured to
operate in cut-through mode when the frame size exceeds
(PKT_MAXBUF_SIZE - ETH_HLEN - ETH_FCS_LEN), which allows transmission
to begin once the FIFO reaches a certain threshold.

Reviewed-by: Wei Fang <wei.fang@nxp.com>
Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Link: https://patch.msgid.link/20250910185211.721341-7-shenwei.wang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Shenwei Wang 2025-09-10 13:52:11 -05:00 • committed by Jakub Kicinski
parent 59e9bf037d
commit d466c16026
2 changed files with 24 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

3
drivers/net/ethernet/freescale/fec.h
View file

@ -514,6 +514,9 @@ struct bufdesc_ex {
*/
#define FEC_QUIRK_HAS_MDIO_C45 BIT(24)
/* Jumbo Frame support */
#define FEC_QUIRK_JUMBO_FRAME BIT(25)
struct bufdesc_prop {
int qid;
/* Address of Rx and Tx buffers */

25
drivers/net/ethernet/freescale/fec_main.c
View file

@ -167,7 +167,8 @@ static const struct fec_devinfo fec_imx8qm_info = {
FEC_QUIRK_ERR007885 | FEC_QUIRK_BUG_CAPTURE |
FEC_QUIRK_HAS_RACC | FEC_QUIRK_HAS_COALESCE |
FEC_QUIRK_CLEAR_SETUP_MII | FEC_QUIRK_HAS_MULTI_QUEUES |
FEC_QUIRK_DELAYED_CLKS_SUPPORT | FEC_QUIRK_HAS_MDIO_C45,
FEC_QUIRK_DELAYED_CLKS_SUPPORT | FEC_QUIRK_HAS_MDIO_C45 |
FEC_QUIRK_JUMBO_FRAME,
};
static const struct fec_devinfo fec_s32v234_info = {
@ -233,6 +234,7 @@ MODULE_PARM_DESC(macaddr, "FEC Ethernet MAC address");
* 2048 byte skbufs are allocated. However, alignment requirements
* varies between FEC variants. Worst case is 64, so round down by 64.
*/
#define MAX_JUMBO_BUF_SIZE (round_down(16384 - FEC_DRV_RESERVE_SPACE - 64, 64))
#define PKT_MAXBUF_SIZE (round_down(2048 - 64, 64))
#define PKT_MINBUF_SIZE 64
@ -1281,8 +1283,18 @@ fec_restart(struct net_device *ndev)
if (fep->quirks & FEC_QUIRK_ENET_MAC) {
/* enable ENET endian swap */
ecntl |= FEC_ECR_BYTESWP;
/* enable ENET store and forward mode */
writel(FEC_TXWMRK_STRFWD, fep->hwp + FEC_X_WMRK);
/* When Jumbo Frame is enabled, the FIFO may not be large enough
* to hold an entire frame. In such cases, if the MTU exceeds
* (PKT_MAXBUF_SIZE - ETH_HLEN - ETH_FCS_LEN), configure the interface
* to operate in cut-through mode, triggered by the FIFO threshold.
* Otherwise, enable the ENET store-and-forward mode.
*/
if ((fep->quirks & FEC_QUIRK_JUMBO_FRAME) &&
(ndev->mtu > (PKT_MAXBUF_SIZE - ETH_HLEN - ETH_FCS_LEN)))
writel(0xF, fep->hwp + FEC_X_WMRK);
else
writel(FEC_TXWMRK_STRFWD, fep->hwp + FEC_X_WMRK);
}
if (fep->bufdesc_ex)
@ -4584,7 +4596,12 @@ fec_probe(struct platform_device *pdev)
fep->pagepool_order = 0;
fep->rx_frame_size = FEC_ENET_RX_FRSIZE;
fep->max_buf_size = PKT_MAXBUF_SIZE;
if (fep->quirks & FEC_QUIRK_JUMBO_FRAME)
fep->max_buf_size = MAX_JUMBO_BUF_SIZE;
else
fep->max_buf_size = PKT_MAXBUF_SIZE;
ndev->max_mtu = fep->max_buf_size - ETH_HLEN - ETH_FCS_LEN;
ret = register_netdev(ndev);