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Message-ID: <CANn89iKVpihmWn8u3AT-zEX0aDU6tD+c9KhjNriTRNxTcofuzg@mail.gmail.com>
Date: Thu, 23 Oct 2025 23:48:41 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Hariprasad Kelam <hkelam@...vell.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>, Jonathan Corbet <corbet@....net>, Sunil Goutham <sgoutham@...vell.com>,
Geetha sowjanya <gakula@...vell.com>, Subbaraya Sundeep <sbhatta@...vell.com>,
Bharat Bhushan <bbhushan2@...vell.com>, Andrew Lunn <andrew+netdev@...n.ch>,
Kory Maincent <kory.maincent@...tlin.com>, Gal Pressman <gal@...dia.com>,
Jianbo Liu <jianbol@...dia.com>, Edward Cree <ecree.xilinx@...il.com>,
Breno Leitao <leitao@...ian.org>
Subject: Re: [RFC net-next] net: loopback: Extend netdev features with new
loopback modes
On Thu, Oct 23, 2025 at 9:49 PM Hariprasad Kelam <hkelam@...vell.com> wrote:
>
> This patch enhances loopback support by exposing new loopback modes
> (e.g., MAC, SERDES) to userspace. These new modes are added extension
> to the existing netdev features.
>
> This allows users to select the loopback at specific layer.
>
> Below are new modes added:
>
> MAC near end loopback
>
> MAC far end loopback
>
> SERDES loopback
>
> Depending on the feedback will submit ethtool changes.
>
> Signed-off-by: Hariprasad Kelam <hkelam@...vell.com>
> ---
> Documentation/networking/netdev-features.rst | 15 +++
> .../ethernet/marvell/octeontx2/nic/otx2_pf.c | 93 ++++++++++++++++++-
> include/linux/netdev_features.h | 9 +-
> net/ethtool/common.c | 3 +
> 4 files changed, 116 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/networking/netdev-features.rst b/Documentation/networking/netdev-features.rst
> index 02bd7536fc0c..dcad5e875f32 100644
> --- a/Documentation/networking/netdev-features.rst
> +++ b/Documentation/networking/netdev-features.rst
> @@ -193,3 +193,18 @@ frames in hardware.
>
> This should be set for devices which support netmem TX. See
> Documentation/networking/netmem.rst
> +
> +* mac-nearend-loopback
> +
> +This requests that the NIC enables MAC nearend loopback i.e egress traffic is
> +routed back to ingress traffic.
> +
> +* mac-farend-loopback
> +
> +This requests that the NIC enables MAC farend loopback i.e ingress traffic is
> +routed back to egress traffic.
> +
> +
> +* serdes-loopback
> +
> +This request that the NIC enables SERDES near end digital loopback.
> diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c
> index e808995703cf..14be6a9206c8 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c
> @@ -1316,6 +1316,84 @@ static int otx2_cgx_config_loopback(struct otx2_nic *pf, bool enable)
> return err;
> }
>
> +static int otx2_cgx_mac_nearend_loopback(struct otx2_nic *pf, bool enable)
> +{
> + struct msg_req *msg;
> + int err;
> +
> + if (enable && !bitmap_empty(pf->flow_cfg->dmacflt_bmap,
> + pf->flow_cfg->dmacflt_max_flows))
> + netdev_warn(pf->netdev,
> + "CGX/RPM nearend loopback might not work as DMAC filters are active\n");
> +
> + mutex_lock(&pf->mbox.lock);
> + if (enable)
> + msg = otx2_mbox_alloc_msg_cgx_intlbk_enable(&pf->mbox);
> + else
> + msg = otx2_mbox_alloc_msg_cgx_intlbk_disable(&pf->mbox);
> +
> + if (!msg) {
> + mutex_unlock(&pf->mbox.lock);
> + return -ENOMEM;
> + }
> +
> + err = otx2_sync_mbox_msg(&pf->mbox);
> + mutex_unlock(&pf->mbox.lock);
> + return err;
> +}
> +
> +static int otx2_cgx_mac_farend_loopback(struct otx2_nic *pf, bool enable)
> +{
> + struct msg_req *msg;
> + int err;
> +
> + if (enable && !bitmap_empty(pf->flow_cfg->dmacflt_bmap,
> + pf->flow_cfg->dmacflt_max_flows))
> + netdev_warn(pf->netdev,
> + "CGX/RPM farend loopback might not work as DMAC filters are active\n");
> +
> + mutex_lock(&pf->mbox.lock);
> + if (enable)
> + msg = otx2_mbox_alloc_msg_cgx_intlbk_enable(&pf->mbox);
> + else
> + msg = otx2_mbox_alloc_msg_cgx_intlbk_disable(&pf->mbox);
> +
> + if (!msg) {
> + mutex_unlock(&pf->mbox.lock);
> + return -ENOMEM;
> + }
> +
> + err = otx2_sync_mbox_msg(&pf->mbox);
> + mutex_unlock(&pf->mbox.lock);
> + return err;
> +}
> +
> +static int otx2_cgx_serdes_loopback(struct otx2_nic *pf, bool enable)
> +{
> + struct msg_req *msg;
> + int err;
> +
> + if (enable && !bitmap_empty(pf->flow_cfg->dmacflt_bmap,
> + pf->flow_cfg->dmacflt_max_flows))
> + netdev_warn(pf->netdev,
> + "CGX/RPM serdes loopback might not work as DMAC filters are active\n");
> +
> + mutex_lock(&pf->mbox.lock);
> + if (enable)
> + msg = otx2_mbox_alloc_msg_cgx_intlbk_enable(&pf->mbox);
> + else
> + msg = otx2_mbox_alloc_msg_cgx_intlbk_disable(&pf->mbox);
> +
> + if (!msg) {
> + mutex_unlock(&pf->mbox.lock);
> + return -ENOMEM;
> + }
> +
> + err = otx2_sync_mbox_msg(&pf->mbox);
> + mutex_unlock(&pf->mbox.lock);
> + return err;
> +}
> +
> int otx2_set_real_num_queues(struct net_device *netdev,
> int tx_queues, int rx_queues)
> {
> @@ -2363,6 +2441,18 @@ static int otx2_set_features(struct net_device *netdev,
> return cn10k_ipsec_ethtool_init(netdev,
> features & NETIF_F_HW_ESP);
>
> + if ((changed & NETIF_F_MAC_LBK_NE) && netif_running(netdev))
> + return otx2_cgx_mac_nearend_loopback(pf,
> + features & NETIF_F_MAC_LBK_NE);
> +
> + if ((changed & NETIF_F_MAC_LBK_FE) && netif_running(netdev))
> + return otx2_cgx_mac_farend_loopback(pf,
> + features & NETIF_F_MAC_LBK_FE);
> +
> + if ((changed & NETIF_F_SERDES_LBK) && netif_running(netdev))
> + return otx2_cgx_serdes_loopback(pf,
> + features & NETIF_F_SERDES_LBK);
> +
> return otx2_handle_ntuple_tc_features(netdev, features);
> }
>
> @@ -3249,7 +3339,8 @@ static int otx2_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> if (pf->flags & OTX2_FLAG_TC_FLOWER_SUPPORT)
> netdev->hw_features |= NETIF_F_HW_TC;
>
> - netdev->hw_features |= NETIF_F_LOOPBACK | NETIF_F_RXALL;
> + netdev->hw_features |= NETIF_F_LOOPBACK | NETIF_F_RXALL |
> + NETIF_F_MAC_LBK_NE | NETIF_F_MAC_LBK_FE | NETIF_F_SERDES_LBK;
>
> netif_set_tso_max_segs(netdev, OTX2_MAX_GSO_SEGS);
> netdev->watchdog_timeo = OTX2_TX_TIMEOUT;
> diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
> index 93e4da7046a1..124f83223361 100644
> --- a/include/linux/netdev_features.h
> +++ b/include/linux/netdev_features.h
> @@ -14,7 +14,7 @@ typedef u64 netdev_features_t;
> enum {
> NETIF_F_SG_BIT, /* Scatter/gather IO. */
> NETIF_F_IP_CSUM_BIT, /* Can checksum TCP/UDP over IPv4. */
> - __UNUSED_NETIF_F_1,
> + NETIF_F_MAC_LBK_NE_BIT, /* MAC near end loopback */
> NETIF_F_HW_CSUM_BIT, /* Can checksum all the packets. */
> NETIF_F_IPV6_CSUM_BIT, /* Can checksum TCP/UDP over IPV6 */
> NETIF_F_HIGHDMA_BIT, /* Can DMA to high memory. */
> @@ -24,8 +24,8 @@ enum {
> NETIF_F_HW_VLAN_CTAG_FILTER_BIT,/* Receive filtering on VLAN CTAGs */
> NETIF_F_VLAN_CHALLENGED_BIT, /* Device cannot handle VLAN packets */
> NETIF_F_GSO_BIT, /* Enable software GSO. */
> - __UNUSED_NETIF_F_12,
> - __UNUSED_NETIF_F_13,
> + NETIF_F_MAC_LBK_FE_BIT, /* MAC far end loopback */
> + NETIF_F_SERDES_LBK_BIT, /* SERDES loopback */
> NETIF_F_GRO_BIT, /* Generic receive offload */
> NETIF_F_LRO_BIT, /* large receive offload */
>
> @@ -165,6 +165,9 @@ enum {
> #define NETIF_F_HW_HSR_TAG_RM __NETIF_F(HW_HSR_TAG_RM)
> #define NETIF_F_HW_HSR_FWD __NETIF_F(HW_HSR_FWD)
> #define NETIF_F_HW_HSR_DUP __NETIF_F(HW_HSR_DUP)
> +#define NETIF_F_MAC_LBK_NE __NETIF_F(MAC_LBK_NE)
> +#define NETIF_F_MAC_LBK_FE __NETIF_F(MAC_LBK_FE)
> +#define NETIF_F_SERDES_LBK __NETIF_F(SERDES_LBK)
>
I do not think we want to burn three generic bits in netdev_features_t
for something which seems device specific.
You have not shown any change for taking care of these features in net/core.
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