From c3e6b2c35b34214c58c1e90d65dab5f5393608e7 Mon Sep 17 00:00:00 2001 From: Aleksander Jan Bajkowski Date: Mon, 3 Jan 2022 20:43:16 +0100 Subject: [PATCH] net: lantiq_xrx200: add ingress SG DMA support This patch adds support for scatter gather DMA. DMA in PMAC splits the packet into several buffers when the MTU on the CPU port is less than the MTU of the switch. The first buffer starts at an offset of NET_IP_ALIGN. In subsequent buffers, dma ignores the offset. Thanks to this patch, the user can still connect to the device in such a situation. For normal configurations, the patch has no effect on performance. Signed-off-by: Aleksander Jan Bajkowski Signed-off-by: David S. Miller --- drivers/net/ethernet/lantiq_xrx200.c | 47 +++++++++++++++++++++++----- 1 file changed, 40 insertions(+), 7 deletions(-) --- a/drivers/net/ethernet/lantiq_xrx200.c +++ b/drivers/net/ethernet/lantiq_xrx200.c @@ -26,6 +26,9 @@ #define XRX200_DMA_RX 0 #define XRX200_DMA_TX 1 +#define XRX200_DMA_PACKET_COMPLETE 0 +#define XRX200_DMA_PACKET_IN_PROGRESS 1 + /* cpu port mac */ #define PMAC_RX_IPG 0x0024 #define PMAC_RX_IPG_MASK 0xf @@ -61,6 +64,9 @@ struct xrx200_chan { struct ltq_dma_channel dma; struct sk_buff *skb[LTQ_DESC_NUM]; + struct sk_buff *skb_head; + struct sk_buff *skb_tail; + struct xrx200_priv *priv; }; @@ -204,7 +210,8 @@ 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]; - int len = (desc->ctl & LTQ_DMA_SIZE_MASK); + u32 ctl = desc->ctl; + int len = (ctl & LTQ_DMA_SIZE_MASK); struct net_device *net_dev = priv->net_dev; int ret; @@ -220,12 +227,36 @@ static int xrx200_hw_receive(struct xrx2 } skb_put(skb, len); - skb->protocol = eth_type_trans(skb, net_dev); - netif_receive_skb(skb); - net_dev->stats.rx_packets++; - net_dev->stats.rx_bytes += len; - return 0; + /* add buffers to skb via skb->frag_list */ + if (ctl & LTQ_DMA_SOP) { + ch->skb_head = skb; + ch->skb_tail = skb; + } 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; + } + + if (ctl & LTQ_DMA_EOP) { + ch->skb_head->protocol = eth_type_trans(ch->skb_head, net_dev); + netif_receive_skb(ch->skb_head); + net_dev->stats.rx_packets++; + net_dev->stats.rx_bytes += ch->skb_head->len; + ch->skb_head = NULL; + ch->skb_tail = NULL; + ret = XRX200_DMA_PACKET_COMPLETE; + } else { + ret = XRX200_DMA_PACKET_IN_PROGRESS; + } + + return ret; } static int xrx200_poll_rx(struct napi_struct *napi, int budget) @@ -240,7 +271,9 @@ static int xrx200_poll_rx(struct napi_st if ((desc->ctl & (LTQ_DMA_OWN | LTQ_DMA_C)) == LTQ_DMA_C) { ret = xrx200_hw_receive(ch); - if (ret) + if (ret == XRX200_DMA_PACKET_IN_PROGRESS) + continue; + if (ret != XRX200_DMA_PACKET_COMPLETE) return ret; rx++; } else {