--- /dev/null
+From e015593573b3e3f74bd8a63c05fa92902194a354 Mon Sep 17 00:00:00 2001
+From: Aleksander Jan Bajkowski <olek2@wp.pl>
+Date: Tue, 4 Jan 2022 16:11:44 +0100
+Subject: [PATCH 715/715] net: lantiq_xrx200: convert to build_skb
+
+We can increase the efficiency of rx path by using buffers to receive
+packets then build SKBs around them just before passing into the network
+stack. In contrast, preallocating SKBs too early reduces CPU cache
+efficiency.
+
+NAT Performance results on BT Home Hub 5A (kernel 5.10.89, mtu 1500):
+
+ Down Up
+Before 577 Mbps 648 Mbps
+After 624 Mbps 695 Mbps
+
+Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
+Signed-off-by: Jakub Kicinski <kuba@kernel.org>
+---
+ drivers/net/ethernet/lantiq_xrx200.c | 56 ++++++++++++++++++----------
+ 1 file changed, 36 insertions(+), 20 deletions(-)
+
+--- a/drivers/net/ethernet/lantiq_xrx200.c
++++ b/drivers/net/ethernet/lantiq_xrx200.c
+@@ -63,7 +63,11 @@ struct xrx200_chan {
+
+ struct napi_struct napi;
+ struct ltq_dma_channel dma;
+- struct sk_buff *skb[LTQ_DESC_NUM];
++
++ union {
++ struct sk_buff *skb[LTQ_DESC_NUM];
++ void *rx_buff[LTQ_DESC_NUM];
++ };
+
+ struct sk_buff *skb_head;
+ struct sk_buff *skb_tail;
+@@ -78,6 +82,7 @@ struct xrx200_priv {
+ struct xrx200_chan chan_rx;
+
+ u16 rx_buf_size;
++ u16 rx_skb_size;
+
+ struct net_device *net_dev;
+ struct device *dev;
+@@ -115,6 +120,12 @@ static int xrx200_buffer_size(int mtu)
+ return round_up(xrx200_max_frame_len(mtu), 4 * XRX200_DMA_BURST_LEN);
+ }
+
++static int xrx200_skb_size(u16 buf_size)
++{
++ return SKB_DATA_ALIGN(buf_size + NET_SKB_PAD + NET_IP_ALIGN) +
++ SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
++}
++
+ /* drop all the packets from the DMA ring */
+ static void xrx200_flush_dma(struct xrx200_chan *ch)
+ {
+@@ -173,30 +184,29 @@ static int xrx200_close(struct net_devic
+ return 0;
+ }
+
+-static int xrx200_alloc_skb(struct xrx200_chan *ch)
++static int xrx200_alloc_buf(struct xrx200_chan *ch, void *(*alloc)(unsigned int size))
+ {
+- struct sk_buff *skb = ch->skb[ch->dma.desc];
++ void *buf = ch->rx_buff[ch->dma.desc];
+ struct xrx200_priv *priv = ch->priv;
+ dma_addr_t mapping;
+ int ret = 0;
+
+- ch->skb[ch->dma.desc] = netdev_alloc_skb_ip_align(priv->net_dev,
+- priv->rx_buf_size);
+- if (!ch->skb[ch->dma.desc]) {
++ ch->rx_buff[ch->dma.desc] = alloc(priv->rx_skb_size);
++ if (!ch->rx_buff[ch->dma.desc]) {
+ ret = -ENOMEM;
+ goto skip;
+ }
+
+- mapping = dma_map_single(priv->dev, ch->skb[ch->dma.desc]->data,
++ mapping = dma_map_single(priv->dev, ch->rx_buff[ch->dma.desc],
+ priv->rx_buf_size, DMA_FROM_DEVICE);
+ if (unlikely(dma_mapping_error(priv->dev, mapping))) {
+- dev_kfree_skb_any(ch->skb[ch->dma.desc]);
+- ch->skb[ch->dma.desc] = skb;
++ skb_free_frag(ch->rx_buff[ch->dma.desc]);
++ ch->rx_buff[ch->dma.desc] = buf;
+ ret = -ENOMEM;
+ goto skip;
+ }
+
+- ch->dma.desc_base[ch->dma.desc].addr = mapping;
++ ch->dma.desc_base[ch->dma.desc].addr = mapping + NET_SKB_PAD + NET_IP_ALIGN;
+ /* Make sure the address is written before we give it to HW */
+ wmb();
+ skip:
+@@ -210,13 +220,14 @@ static int xrx200_hw_receive(struct xrx2
+ {
+ struct xrx200_priv *priv = ch->priv;
+ struct ltq_dma_desc *desc = &ch->dma.desc_base[ch->dma.desc];
+- struct sk_buff *skb = ch->skb[ch->dma.desc];
++ void *buf = ch->rx_buff[ch->dma.desc];
+ u32 ctl = desc->ctl;
+ int len = (ctl & LTQ_DMA_SIZE_MASK);
+ struct net_device *net_dev = priv->net_dev;
++ struct sk_buff *skb;
+ int ret;
+
+- ret = xrx200_alloc_skb(ch);
++ ret = xrx200_alloc_buf(ch, napi_alloc_frag);
+
+ ch->dma.desc++;
+ ch->dma.desc %= LTQ_DESC_NUM;
+@@ -227,19 +238,21 @@ static int xrx200_hw_receive(struct xrx2
+ return ret;
+ }
+
++ skb = build_skb(buf, priv->rx_skb_size);
++ skb_reserve(skb, NET_SKB_PAD);
+ skb_put(skb, len);
+
+ /* add buffers to skb via skb->frag_list */
+ if (ctl & LTQ_DMA_SOP) {
+ ch->skb_head = skb;
+ ch->skb_tail = skb;
++ skb_reserve(skb, NET_IP_ALIGN);
+ } else if (ch->skb_head) {
+ if (ch->skb_head == ch->skb_tail)
+ skb_shinfo(ch->skb_tail)->frag_list = skb;
+ else
+ ch->skb_tail->next = skb;
+ ch->skb_tail = skb;
+- skb_reserve(ch->skb_tail, -NET_IP_ALIGN);
+ ch->skb_head->len += skb->len;
+ ch->skb_head->data_len += skb->len;
+ ch->skb_head->truesize += skb->truesize;
+@@ -395,12 +408,13 @@ xrx200_change_mtu(struct net_device *net
+ struct xrx200_chan *ch_rx = &priv->chan_rx;
+ int old_mtu = net_dev->mtu;
+ bool running = false;
+- struct sk_buff *skb;
++ void *buff;
+ int curr_desc;
+ int ret = 0;
+
+ net_dev->mtu = new_mtu;
+ priv->rx_buf_size = xrx200_buffer_size(new_mtu);
++ priv->rx_skb_size = xrx200_skb_size(priv->rx_buf_size);
+
+ if (new_mtu <= old_mtu)
+ return ret;
+@@ -416,14 +430,15 @@ xrx200_change_mtu(struct net_device *net
+
+ for (ch_rx->dma.desc = 0; ch_rx->dma.desc < LTQ_DESC_NUM;
+ ch_rx->dma.desc++) {
+- skb = ch_rx->skb[ch_rx->dma.desc];
+- ret = xrx200_alloc_skb(ch_rx);
++ buff = ch_rx->rx_buff[ch_rx->dma.desc];
++ ret = xrx200_alloc_buf(ch_rx, netdev_alloc_frag);
+ if (ret) {
+ net_dev->mtu = old_mtu;
+ priv->rx_buf_size = xrx200_buffer_size(old_mtu);
++ priv->rx_skb_size = xrx200_skb_size(priv->rx_buf_size);
+ break;
+ }
+- dev_kfree_skb_any(skb);
++ skb_free_frag(buff);
+ }
+
+ ch_rx->dma.desc = curr_desc;
+@@ -476,7 +491,7 @@ static int xrx200_dma_init(struct xrx200
+ ltq_dma_alloc_rx(&ch_rx->dma);
+ for (ch_rx->dma.desc = 0; ch_rx->dma.desc < LTQ_DESC_NUM;
+ ch_rx->dma.desc++) {
+- ret = xrx200_alloc_skb(ch_rx);
++ ret = xrx200_alloc_buf(ch_rx, netdev_alloc_frag);
+ if (ret)
+ goto rx_free;
+ }
+@@ -511,7 +526,7 @@ rx_ring_free:
+ /* free the allocated RX ring */
+ for (i = 0; i < LTQ_DESC_NUM; i++) {
+ if (priv->chan_rx.skb[i])
+- dev_kfree_skb_any(priv->chan_rx.skb[i]);
++ skb_free_frag(priv->chan_rx.rx_buff[i]);
+ }
+
+ rx_free:
+@@ -528,7 +543,7 @@ static void xrx200_hw_cleanup(struct xrx
+
+ /* free the allocated RX ring */
+ for (i = 0; i < LTQ_DESC_NUM; i++)
+- dev_kfree_skb_any(priv->chan_rx.skb[i]);
++ skb_free_frag(priv->chan_rx.rx_buff[i]);
+ }
+
+ static int xrx200_probe(struct platform_device *pdev)
+@@ -554,6 +569,7 @@ static int xrx200_probe(struct platform_
+ net_dev->min_mtu = ETH_ZLEN;
+ net_dev->max_mtu = XRX200_DMA_DATA_LEN - xrx200_max_frame_len(0);
+ priv->rx_buf_size = xrx200_buffer_size(ETH_DATA_LEN);
++ priv->rx_skb_size = xrx200_skb_size(priv->rx_buf_size);
+
+ /* load the memory ranges */
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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