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Date: Wed, 12 Jun 2024 10:36:38 +0000
From: Hariprasad Kelam <hkelam@...vell.com>
To: Justin Lai <justinlai0215@...ltek.com>,
"kuba@...nel.org"
<kuba@...nel.org>
CC: "davem@...emloft.net" <davem@...emloft.net>,
"edumazet@...gle.com"
<edumazet@...gle.com>,
"pabeni@...hat.com" <pabeni@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"andrew@...n.ch"
<andrew@...n.ch>,
"jiri@...nulli.us" <jiri@...nulli.us>,
"horms@...nel.org"
<horms@...nel.org>,
Ratheesh Kannoth <rkannoth@...vell.com>,
Ping-Ke Shih
<pkshih@...ltek.com>,
Larry Chiu <larry.chiu@...ltek.com>
Subject: RE: [PATCH net-next v20 06/13] rtase: Implement .ndo_start_xmit
function
> > > Implement .ndo_start_xmit function to fill the information of the
> > > packet to be transmitted into the tx descriptor, and then the
> > > hardware will transmit the packet using the information in the tx
> descriptor.
> > > In addition, we also implemented the tx_handler function to enable
> > > the tx descriptor to be reused.
> > >
> > > Signed-off-by: Justin Lai <justinlai0215@...ltek.com>
> > > ---
> > > .../net/ethernet/realtek/rtase/rtase_main.c | 285 ++++++++++++++++++
> > > 1 file changed, 285 insertions(+)
> > >
> > > diff --git a/drivers/net/ethernet/realtek/rtase/rtase_main.c
> > > b/drivers/net/ethernet/realtek/rtase/rtase_main.c
> > > index 23406c195cff..6bdb4edbfbc1 100644
> > > --- a/drivers/net/ethernet/realtek/rtase/rtase_main.c
> > > +++ b/drivers/net/ethernet/realtek/rtase/rtase_main.c
> > > @@ -256,6 +256,68 @@ static void rtase_mark_to_asic(union
> > > rtase_rx_desc *desc, u32 rx_buf_sz)
> > > cpu_to_le32(RTASE_DESC_OWN | eor | rx_buf_sz)); }
> > >
> > > +static u32 rtase_tx_avail(struct rtase_ring *ring) {
> > > + return READ_ONCE(ring->dirty_idx) + RTASE_NUM_DESC -
> > > + READ_ONCE(ring->cur_idx); }
> > > +
> > > +static int tx_handler(struct rtase_ring *ring, int budget) {
> > > + const struct rtase_private *tp = ring->ivec->tp;
> > > + struct net_device *dev = tp->dev;
> > > + u32 dirty_tx, tx_left;
> > > + u32 bytes_compl = 0;
> > > + u32 pkts_compl = 0;
> > > + int workdone = 0;
> > > +
> > > + dirty_tx = ring->dirty_idx;
> > > + tx_left = READ_ONCE(ring->cur_idx) - dirty_tx;
> > > +
> > > + while (tx_left > 0) {
> > > + u32 entry = dirty_tx % RTASE_NUM_DESC;
> > > + struct rtase_tx_desc *desc = ring->desc +
> > > + sizeof(struct rtase_tx_desc) *
> > entry;
> > > + u32 status;
> > > +
> > > + status = le32_to_cpu(desc->opts1);
> > > +
> > > + if (status & RTASE_DESC_OWN)
> > > + break;
> > > +
> > > + rtase_unmap_tx_skb(tp->pdev, ring->mis.len[entry], desc);
> > > + ring->mis.len[entry] = 0;
> > > + if (ring->skbuff[entry]) {
> > > + pkts_compl++;
> > > + bytes_compl += ring->skbuff[entry]->len;
> > > + napi_consume_skb(ring->skbuff[entry], budget);
> > > + ring->skbuff[entry] = NULL;
> > > + }
> > > +
> > > + dirty_tx++;
> > > + tx_left--;
> > > + workdone++;
> > > +
> > > + if (workdone == RTASE_TX_BUDGET_DEFAULT)
> > > + break;
> > > + }
> > > +
> > > + if (ring->dirty_idx != dirty_tx) {
> > > + dev_sw_netstats_tx_add(dev, pkts_compl, bytes_compl);
> > > + WRITE_ONCE(ring->dirty_idx, dirty_tx);
> > > +
> > > + netif_subqueue_completed_wake(dev, ring->index,
> > > pkts_compl,
> > > + bytes_compl,
> > > + rtase_tx_avail(ring),
> > > +
> > RTASE_TX_START_THRS);
> > > +
> > > + if (ring->cur_idx != dirty_tx)
> > > + rtase_w8(tp, RTASE_TPPOLL, BIT(ring->index));
> > > + }
> > > +
> > > + return 0;
> > > +}
> > > +
> > > static void rtase_tx_desc_init(struct rtase_private *tp, u16 idx) {
> > > struct rtase_ring *ring = &tp->tx_ring[idx]; @@ -1014,6
> > > +1076,228 @@ static int rtase_close(struct net_device *dev)
> > > return 0;
> > > }
> > >
> > > +static u32 rtase_tx_vlan_tag(const struct rtase_private *tp,
> > > + const struct sk_buff *skb) {
> > > + return (skb_vlan_tag_present(skb)) ?
> > > + (RTASE_TX_VLAN_TAG | swab16(skb_vlan_tag_get(skb))) :
> > > 0x00; }
> > > +
> > Vlan protocol can be either 0x8100 or 0x88A8, how does
> > hardware know which header to insert?
> > Thanks,
> > Hariprasad k
>
> We only allow the hardware to add 0x8100, the VLAN must at least have
> 0x8100 to potentially have 0x88a8, skb_vlan_tag_present indicates that VLAN
> exists, hence at least the 0x8100 VLAN would exist.
> >
Thanks for the explanation, but one question which bothers me is that "how hardware knows offset with in the packet"
For example
Case 1: DMAC + SMAC + 8100 VLAN_ID + IP
Here offset is right after the SMAC.
Case 2: DMAC + SMAC + 88A8 VLAN_ID + 8100 VLAN_ID + IP
Here offset is right after first vlan tag.
Thanks,
Hariprasad k
> > > +static u32 rtase_tx_csum(struct sk_buff *skb, const struct
> > > +net_device
> > > +*dev) {
> > > + u32 csum_cmd = 0;
> > > + u8 ip_protocol;
> > > +
> > > + switch (vlan_get_protocol(skb)) {
> > > + case htons(ETH_P_IP):
> > > + csum_cmd = RTASE_TX_IPCS_C;
> > > + ip_protocol = ip_hdr(skb)->protocol;
> > > + break;
> > > +
> > > + case htons(ETH_P_IPV6):
> > > + csum_cmd = RTASE_TX_IPV6F_C;
> > > + ip_protocol = ipv6_hdr(skb)->nexthdr;
> > > + break;
> > > +
> > > + default:
> > > + ip_protocol = IPPROTO_RAW;
> > > + break;
> > > + }
> > > +
> > > + if (ip_protocol == IPPROTO_TCP)
> > > + csum_cmd |= RTASE_TX_TCPCS_C;
> > > + else if (ip_protocol == IPPROTO_UDP)
> > > + csum_cmd |= RTASE_TX_UDPCS_C;
> > > +
> > > + csum_cmd |= u32_encode_bits(skb_transport_offset(skb),
> > > + RTASE_TCPHO_MASK);
> > > +
> > > + return csum_cmd;
> > > +}
> > > +
> > > +static int rtase_xmit_frags(struct rtase_ring *ring, struct sk_buff *skb,
> > > + u32 opts1, u32 opts2) {
> > > + const struct skb_shared_info *info = skb_shinfo(skb);
> > > + const struct rtase_private *tp = ring->ivec->tp;
> > > + const u8 nr_frags = info->nr_frags;
> > > + struct rtase_tx_desc *txd = NULL;
> > > + u32 cur_frag, entry;
> > > +
> > > + entry = ring->cur_idx;
> > > + for (cur_frag = 0; cur_frag < nr_frags; cur_frag++) {
> > > + const skb_frag_t *frag = &info->frags[cur_frag];
> > > + dma_addr_t mapping;
> > > + u32 status, len;
> > > + void *addr;
> > > +
> > > + entry = (entry + 1) % RTASE_NUM_DESC;
> > > +
> > > + txd = ring->desc + sizeof(struct rtase_tx_desc) * entry;
> > > + len = skb_frag_size(frag);
> > > + addr = skb_frag_address(frag);
> > > + mapping = dma_map_single(&tp->pdev->dev, addr, len,
> > > + DMA_TO_DEVICE);
> > > +
> > > + if (unlikely(dma_mapping_error(&tp->pdev->dev,
> > > + mapping)))
> > > {
> > > + if (unlikely(net_ratelimit()))
> > > + netdev_err(tp->dev,
> > > + "Failed to map TX
> > fragments
> > > DMA!\n");
> > > +
> > > + goto err_out;
> > > + }
> > > +
> > > + if (((entry + 1) % RTASE_NUM_DESC) == 0)
> > > + status = (opts1 | len | RTASE_RING_END);
> > > + else
> > > + status = opts1 | len;
> > > +
> > > + if (cur_frag == (nr_frags - 1)) {
> > > + ring->skbuff[entry] = skb;
> > > + status |= RTASE_TX_LAST_FRAG;
> > > + }
> > > +
> > > + ring->mis.len[entry] = len;
> > > + txd->addr = cpu_to_le64(mapping);
> > > + txd->opts2 = cpu_to_le32(opts2);
> > > +
> > > + /* make sure the operating fields have been updated */
> > > + dma_wmb();
> > > + txd->opts1 = cpu_to_le32(status);
> > > + }
> > > +
> > > + return cur_frag;
> > > +
> > > +err_out:
> > > + rtase_tx_clear_range(ring, ring->cur_idx + 1, cur_frag);
> > > + return -EIO;
> > > +}
> > > +
> > > +static netdev_tx_t rtase_start_xmit(struct sk_buff *skb,
> > > + struct net_device *dev) {
> > > + struct skb_shared_info *shinfo = skb_shinfo(skb);
> > > + struct rtase_private *tp = netdev_priv(dev);
> > > + u32 q_idx, entry, len, opts1, opts2;
> > > + struct netdev_queue *tx_queue;
> > > + bool stop_queue, door_bell;
> > > + u32 mss = shinfo->gso_size;
> > > + struct rtase_tx_desc *txd;
> > > + struct rtase_ring *ring;
> > > + dma_addr_t mapping;
> > > + int frags;
> > > +
> > > + /* multiqueues */
> > > + q_idx = skb_get_queue_mapping(skb);
> > > + ring = &tp->tx_ring[q_idx];
> > > + tx_queue = netdev_get_tx_queue(dev, q_idx);
> > > +
> > > + if (unlikely(!rtase_tx_avail(ring))) {
> > > + if (net_ratelimit())
> > > + netdev_err(dev, "BUG! Tx Ring full when queue
> > > awake!\n");
> > > + goto err_stop;
> > > + }
> > > +
> > > + entry = ring->cur_idx % RTASE_NUM_DESC;
> > > + txd = ring->desc + sizeof(struct rtase_tx_desc) * entry;
> > > +
> > > + opts1 = RTASE_DESC_OWN;
> > > + opts2 = rtase_tx_vlan_tag(tp, skb);
> > > +
> > > + /* tcp segmentation offload (or tcp large send) */
> > > + if (mss) {
> > > + if (shinfo->gso_type & SKB_GSO_TCPV4) {
> > > + opts1 |= RTASE_GIANT_SEND_V4;
> > > + } else if (shinfo->gso_type & SKB_GSO_TCPV6) {
> > > + if (skb_cow_head(skb, 0))
> > > + goto err_dma_0;
> > > +
> > > + tcp_v6_gso_csum_prep(skb);
> > > + opts1 |= RTASE_GIANT_SEND_V6;
> > > + } else {
> > > + WARN_ON_ONCE(1);
> > > + }
> > > +
> > > + opts1 |= u32_encode_bits(skb_transport_offset(skb),
> > > + RTASE_TCPHO_MASK);
> > > + opts2 |= u32_encode_bits(mss, RTASE_MSS_MASK);
> > > + } else if (skb->ip_summed == CHECKSUM_PARTIAL) {
> > > + opts2 |= rtase_tx_csum(skb, dev);
> > > + }
> > > +
> > > + frags = rtase_xmit_frags(ring, skb, opts1, opts2);
> > > + if (unlikely(frags < 0))
> > > + goto err_dma_0;
> > > +
> > > + if (frags) {
> > > + len = skb_headlen(skb);
> > > + opts1 |= RTASE_TX_FIRST_FRAG;
> > > + } else {
> > > + len = skb->len;
> > > + ring->skbuff[entry] = skb;
> > > + opts1 |= RTASE_TX_FIRST_FRAG | RTASE_TX_LAST_FRAG;
> > > + }
> > > +
> > > + if (((entry + 1) % RTASE_NUM_DESC) == 0)
> > > + opts1 |= (len | RTASE_RING_END);
> > > + else
> > > + opts1 |= len;
> > > +
> > > + mapping = dma_map_single(&tp->pdev->dev, skb->data, len,
> > > + DMA_TO_DEVICE);
> > > +
> > > + if (unlikely(dma_mapping_error(&tp->pdev->dev, mapping))) {
> > > + if (unlikely(net_ratelimit()))
> > > + netdev_err(dev, "Failed to map TX DMA!\n");
> > > +
> > > + goto err_dma_1;
> > > + }
> > > +
> > > + ring->mis.len[entry] = len;
> > > + txd->addr = cpu_to_le64(mapping);
> > > + txd->opts2 = cpu_to_le32(opts2);
> > > + txd->opts1 = cpu_to_le32(opts1 & ~RTASE_DESC_OWN);
> > > +
> > > + /* make sure the operating fields have been updated */
> > > + dma_wmb();
> > > +
> > > + door_bell = __netdev_tx_sent_queue(tx_queue, skb->len,
> > > + netdev_xmit_more());
> > > +
> > > + txd->opts1 = cpu_to_le32(opts1);
> > > +
> > > + skb_tx_timestamp(skb);
> > > +
> > > + /* tx needs to see descriptor changes before updated cur_idx */
> > > + smp_wmb();
> > > +
> > > + WRITE_ONCE(ring->cur_idx, ring->cur_idx + frags + 1);
> > > +
> > > + stop_queue = !netif_subqueue_maybe_stop(dev, ring->index,
> > > + rtase_tx_avail(ring),
> > > +
> > RTASE_TX_STOP_THRS,
> > > +
> > RTASE_TX_START_THRS);
> > > +
> > > + if (door_bell || stop_queue)
> > > + rtase_w8(tp, RTASE_TPPOLL, BIT(ring->index));
> > > +
> > > + return NETDEV_TX_OK;
> > > +
> > > +err_dma_1:
> > > + ring->skbuff[entry] = NULL;
> > > + rtase_tx_clear_range(ring, ring->cur_idx + 1, frags);
> > > +
> > > +err_dma_0:
> > > + dev->stats.tx_dropped++;
> > > + dev_kfree_skb_any(skb);
> > > + return NETDEV_TX_OK;
> > > +
> > > +err_stop:
> > > + netif_stop_queue(dev);
> > > + dev->stats.tx_dropped++;
> > > + return NETDEV_TX_BUSY;
> > > +}
> > > +
> > > static void rtase_enable_eem_write(const struct rtase_private *tp) {
> > > u8 val;
> > > @@ -1065,6 +1349,7 @@ static void rtase_netpoll(struct net_device
> > > *dev) static const struct net_device_ops rtase_netdev_ops = {
> > > .ndo_open = rtase_open,
> > > .ndo_stop = rtase_close,
> > > + .ndo_start_xmit = rtase_start_xmit,
> > > #ifdef CONFIG_NET_POLL_CONTROLLER
> > > .ndo_poll_controller = rtase_netpoll, #endif
> > > --
> > > 2.34.1
> > >
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