> -----Original Message-----
> From: Jakub Kicinski <[email protected]>
> Sent: Friday, January 9, 2026 8:56 PM
> To: Haiyang Zhang <[email protected]>
> Cc: [email protected]; [email protected]; KY Srinivasan
> <[email protected]>; Haiyang Zhang <[email protected]>; Wei Liu
> <[email protected]>; Dexuan Cui <[email protected]>; Long Li
> <[email protected]>; Andrew Lunn <[email protected]>; David S.
> Miller <[email protected]>; Eric Dumazet <[email protected]>; Paolo
> Abeni <[email protected]>; Konstantin Taranov <[email protected]>;
> Simon Horman <[email protected]>; Erni Sri Satya Vennela
> <[email protected]>; Shradha Gupta
> <[email protected]>; Saurabh Sengar
> <[email protected]>; Aditya Garg
> <[email protected]>; Dipayaan Roy
> <[email protected]>; Shiraz Saleem
> <[email protected]>; [email protected]; linux-
> [email protected]; Paul Rosswurm <[email protected]>
> Subject: [EXTERNAL] Re: [PATCH V2,net-next, 1/2] net: mana: Add support
> for coalesced RX packets on CQE
>
> On Tue, 6 Jan 2026 12:46:46 -0800 Haiyang Zhang wrote:
> > From: Haiyang Zhang <[email protected]>
> >
> > Our NIC can have up to 4 RX packets on 1 CQE. To support this feature,
> > check and process the type CQE_RX_COALESCED_4. The default setting is
> > disabled, to avoid possible regression on latency.
> >
> > And add ethtool handler to switch this feature. To turn it on, run:
> > ethtool -C <nic> rx-frames 4
> > To turn it off:
> > ethtool -C <nic> rx-frames 1
>
> Exposing just rx frame count, and only two values is quite unusual.
> Please explain in more detail the coalescing logic of the device.
Our NIC device only supports coalescing on RX. And when it's disabled each
RX CQE indicates 1 RX packet; when enabled each RX CQE indicates up to 4
packets.
>
> > @@ -2079,14 +2081,10 @@ static void mana_process_rx_cqe(struct mana_rxq
> *rxq, struct mana_cq *cq,
> > return;
> > }
> >
> > - pktlen = oob->ppi[0].pkt_len;
> > -
> > - if (pktlen == 0) {
> > - /* data packets should never have packetlength of zero */
> > - netdev_err(ndev, "RX pkt len=0, rq=%u, cq=%u, rxobj=0x%llx\n",
> > - rxq->gdma_id, cq->gdma_id, rxq->rxobj);
> > +nextpkt:
> > + pktlen = oob->ppi[i].pkt_len;
> > + if (pktlen == 0)
> > return;
> > - }
> >
> > curr = rxq->buf_index;
> > rxbuf_oob = &rxq->rx_oobs[curr];
> > @@ -2097,12 +2095,15 @@ static void mana_process_rx_cqe(struct mana_rxq
> *rxq, struct mana_cq *cq,
> > /* Unsuccessful refill will have old_buf == NULL.
> > * In this case, mana_rx_skb() will drop the packet.
> > */
> > - mana_rx_skb(old_buf, old_fp, oob, rxq);
> > + mana_rx_skb(old_buf, old_fp, oob, rxq, i);
> >
> > drop:
> > mana_move_wq_tail(rxq->gdma_rq, rxbuf_oob->wqe_inf.wqe_size_in_bu);
> >
> > mana_post_pkt_rxq(rxq);
> > +
> > + if (coalesced && (++i < MANA_RXCOMP_OOB_NUM_PPI))
> > + goto nextpkt;
>
> Please code this up as a loop. Using gotos for control flow other than
> to jump to error handling epilogues is a poor coding practice (see the
> kernel coding style).
Will do.
>
> > +static int mana_set_coalesce(struct net_device *ndev,
> > + struct ethtool_coalesce *ec,
> > + struct kernel_ethtool_coalesce *kernel_coal,
> > + struct netlink_ext_ack *extack)
> > +{
> > + struct mana_port_context *apc = netdev_priv(ndev);
> > + u8 saved_cqe_coalescing_enable;
> > + int err;
> > +
> > + if (ec->rx_max_coalesced_frames != 1 &&
> > + ec->rx_max_coalesced_frames != MANA_RXCOMP_OOB_NUM_PPI) {
> > + NL_SET_ERR_MSG_FMT(extack,
> > + "rx-frames must be 1 or %u, got %u",
> > + MANA_RXCOMP_OOB_NUM_PPI,
> > + ec->rx_max_coalesced_frames);
> > + return -EINVAL;
> > + }
> > +
> > + saved_cqe_coalescing_enable = apc->cqe_coalescing_enable;
> > + apc->cqe_coalescing_enable =
> > + ec->rx_max_coalesced_frames == MANA_RXCOMP_OOB_NUM_PPI;
> > +
> > + if (!apc->port_is_up)
> > + return 0;
> > +
> > + err = mana_config_rss(apc, TRI_STATE_TRUE, false, false);
> > +
>
> unnecessary empty line
Will rm.
>
> > + if (err) {
> > + netdev_err(ndev, "Set rx-frames to %u failed:%d\n",
> > + ec->rx_max_coalesced_frames, err);
> > + NL_SET_ERR_MSG_FMT(extack, "Set rx-frames to %u failed",
> > + ec->rx_max_coalesced_frames);
>
> These messages are both pointless. If HW communication has failed
> presumably there will already be an error in the logs. The extack
> gives the user no information they wouldn't already have.
Will rm.
Thanks,
- Haiyang
