RE: [PATCH v6 net-next 6/6] net: fec: enable the Jumbo frame support for i.MX8QM

[Wei Fang]

> 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.
> 
> Signed-off-by: Shenwei Wang <shenwei.wang@xxxxxxx>
> ---
>  drivers/net/ethernet/freescale/fec.h      |  3 +++
>  drivers/net/ethernet/freescale/fec_main.c | 25 +++++++++++++++++++----
>  2 files changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec.h
> b/drivers/net/ethernet/freescale/fec.h
> index 0127cfa5529f..41e0d85d15da 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
> @@ -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 */
> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index a2aa08afa4bd..329320395285 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -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
> 
> @@ -1279,8 +1281,18 @@ 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)
> @@ -4581,7 +4593,12 @@ 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);
> --
> 2.43.0

Reviewed-by: Wei Fang <wei.fang@xxxxxxx>