Re: [PATCH net-next v24 06/10] net: dsa: tag_mtk: add Airoha variant usage of this TAG

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] net: dsa: MAC driver offloads fail for new Airoha tag protocol
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commit 8cdc1e6c2d15d8ca09e78024f7070167218dff24
Author: Christian Marangi <ansuelsmth@gmail.com>

    net: dsa: tag_mtk: add Airoha variant usage of this TAG
    
    Add variant of the MTK TAG for Airoha Switch and comments about difference
    between Airoha AN8855 and Mediatek tag bitmap.

> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index 5d12191b6f6f5..9824c63ad50b3 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -76,6 +77,7 @@ enum dsa_tag_protocol {
>  	DSA_TAG_PROTO_KSZ9893		= DSA_TAG_PROTO_KSZ9893_VALUE,
>  	DSA_TAG_PROTO_LAN9303		= DSA_TAG_PROTO_LAN9303_VALUE,
>  	DSA_TAG_PROTO_MTK		= DSA_TAG_PROTO_MTK_VALUE,
> +	DSA_TAG_PROTO_AIROHA		= DSA_TAG_PROTO_AIROHA_VALUE,

[Severity: High]
Does this new protocol ID break hardware offloading and DMA descriptor
construction in existing drivers?

Several MAC drivers currently hardcode checks for DSA_TAG_PROTO_MTK and will
silently fail or reject this new protocol.

In the Airoha Ethernet driver, returning 0 breaks DMA descriptor construction:

drivers/net/ethernet/airoha/airoha_eth.c:airoha_get_dsa_tag() {
	if (dev->dsa_ptr->tag_ops->proto != DSA_TAG_PROTO_MTK)
		return 0;
}

In the Mediatek Ethernet driver, metadata allocation for hardware forwarding
fails because mtk_uses_dsa() returns false:

drivers/net/ethernet/mediatek/mtk_eth_soc.c:mtk_uses_dsa() {
	return netdev_uses_dsa(dev) &&
	       dev->dsa_ptr->tag_ops->proto == DSA_TAG_PROTO_MTK;
}

PPE hardware offloading silently aborts instead of forwarding:

drivers/net/ethernet/mediatek/mtk_ppe.c:mtk_foe_entry_prepare() {
	if (!netdev_uses_dsa(skb->dev) ||
	    skb->dev->dsa_ptr->tag_ops->proto != DSA_TAG_PROTO_MTK)
		goto out;
}

And flow offloading completely fails:

drivers/net/ethernet/mediatek/mtk_ppe_offload.c:mtk_flow_get_dsa_port() {
	if (dp->cpu_dp->tag_ops->proto != DSA_TAG_PROTO_MTK)
		return -ENODEV;
}

Do these drivers need to be updated to also accept DSA_TAG_PROTO_AIROHA?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260928194511.41878-1-ansuelsmth@gmail.com?part=6