atl1c: Work around the DMA RX overflow issue

This is based on alx driver commit 881d0327db37 ("net: alx: Work around
the DMA RX overflow issue").

The alx and atl1c drivers had RX overflow error which was why a custom
allocator was created to avoid certain addresses. The simpler workaround
then created for alx driver, but not for atl1c due to lack of tester.

Instead of using a custom allocator, check the allocated skb address and
use skb_reserve() to move away from problematic 0x...fc0 address.

Tested on AR8131 on Acer 4540.

Signed-off-by: Sieng-Piaw Liew <liew.s.piaw@gmail.com>
Link: https://lore.kernel.org/r/20230912010711.12036-1-liew.s.piaw@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c.h b/drivers/net/ethernet/atheros/atl1c/atl1c.h
index 43d821fe7a5424aaba322f514fa3949fa9107c68..63ba64dbb731071edbb7bf015e8422df8b8a79dd 100644 (file)
--- a/drivers/net/ethernet/atheros/atl1c/atl1c.h
+++ b/drivers/net/ethernet/atheros/atl1c/atl1c.h
@@ -504,15 +504,12 @@ struct atl1c_rrd_ring {
        u16 next_to_use;
        u16 next_to_clean;
        struct napi_struct napi;
-       struct page *rx_page;
-       unsigned int rx_page_offset;
 };
 
 /* board specific private data structure */
 struct atl1c_adapter {
        struct net_device   *netdev;
        struct pci_dev      *pdev;
-       unsigned int        rx_frag_size;
        struct atl1c_hw        hw;
        struct atl1c_hw_stats  hw_stats;
        struct mii_if_info  mii;    /* MII interface info */

diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
index 940c5d1ff9cfcef2269f423af5130e0fc29195f3..74b78164cf74a8ec053b40420412080252b459a7 100644 (file)
--- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
+++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
@@ -483,15 +483,10 @@ static int atl1c_set_mac_addr(struct net_device *netdev, void *p)
 static void atl1c_set_rxbufsize(struct atl1c_adapter *adapter,
                                struct net_device *dev)
 {
-       unsigned int head_size;
        int mtu = dev->mtu;
 
        adapter->rx_buffer_len = mtu > AT_RX_BUF_SIZE ?
                roundup(mtu + ETH_HLEN + ETH_FCS_LEN + VLAN_HLEN, 8) : AT_RX_BUF_SIZE;
-
-       head_size = SKB_DATA_ALIGN(adapter->rx_buffer_len + NET_SKB_PAD + NET_IP_ALIGN) +
-                   SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
-       adapter->rx_frag_size = roundup_pow_of_two(head_size);
 }
 
 static netdev_features_t atl1c_fix_features(struct net_device *netdev,
@@ -964,7 +959,6 @@ static void atl1c_init_ring_ptrs(struct atl1c_adapter *adapter)
 static void atl1c_free_ring_resources(struct atl1c_adapter *adapter)
 {
        struct pci_dev *pdev = adapter->pdev;
-       int i;
 
        dma_free_coherent(&pdev->dev, adapter->ring_header.size,
                          adapter->ring_header.desc, adapter->ring_header.dma);
@@ -977,12 +971,6 @@ static void atl1c_free_ring_resources(struct atl1c_adapter *adapter)
                kfree(adapter->tpd_ring[0].buffer_info);
                adapter->tpd_ring[0].buffer_info = NULL;
        }
-       for (i = 0; i < adapter->rx_queue_count; ++i) {
-               if (adapter->rrd_ring[i].rx_page) {
-                       put_page(adapter->rrd_ring[i].rx_page);
-                       adapter->rrd_ring[i].rx_page = NULL;
-               }
-       }
 }
 
 /**
@@ -1754,48 +1742,11 @@ static inline void atl1c_rx_checksum(struct atl1c_adapter *adapter,
        skb_checksum_none_assert(skb);
 }
 
-static struct sk_buff *atl1c_alloc_skb(struct atl1c_adapter *adapter,
-                                      u32 queue, bool napi_mode)
-{
-       struct atl1c_rrd_ring *rrd_ring = &adapter->rrd_ring[queue];
-       struct sk_buff *skb;
-       struct page *page;
-
-       if (adapter->rx_frag_size > PAGE_SIZE) {
-               if (likely(napi_mode))
-                       return napi_alloc_skb(&rrd_ring->napi,
-                                             adapter->rx_buffer_len);
-               else
-                       return netdev_alloc_skb_ip_align(adapter->netdev,
-                                                        adapter->rx_buffer_len);
-       }
-
-       page = rrd_ring->rx_page;
-       if (!page) {
-               page = alloc_page(GFP_ATOMIC);
-               if (unlikely(!page))
-                       return NULL;
-               rrd_ring->rx_page = page;
-               rrd_ring->rx_page_offset = 0;
-       }
-
-       skb = build_skb(page_address(page) + rrd_ring->rx_page_offset,
-                       adapter->rx_frag_size);
-       if (likely(skb)) {
-               skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
-               rrd_ring->rx_page_offset += adapter->rx_frag_size;
-               if (rrd_ring->rx_page_offset >= PAGE_SIZE)
-                       rrd_ring->rx_page = NULL;
-               else
-                       get_page(page);
-       }
-       return skb;
-}
-
 static int atl1c_alloc_rx_buffer(struct atl1c_adapter *adapter, u32 queue,
                                 bool napi_mode)
 {
        struct atl1c_rfd_ring *rfd_ring = &adapter->rfd_ring[queue];
+       struct atl1c_rrd_ring *rrd_ring = &adapter->rrd_ring[queue];
        struct pci_dev *pdev = adapter->pdev;
        struct atl1c_buffer *buffer_info, *next_info;
        struct sk_buff *skb;
@@ -1814,13 +1765,27 @@ static int atl1c_alloc_rx_buffer(struct atl1c_adapter *adapter, u32 queue,
        while (next_info->flags & ATL1C_BUFFER_FREE) {
                rfd_desc = ATL1C_RFD_DESC(rfd_ring, rfd_next_to_use);
 
-               skb = atl1c_alloc_skb(adapter, queue, napi_mode);
+               /* When DMA RX address is set to something like
+                * 0x....fc0, it will be very likely to cause DMA
+                * RFD overflow issue.
+                *
+                * To work around it, we apply rx skb with 64 bytes
+                * longer space, and offset the address whenever
+                * 0x....fc0 is detected.
+                */
+               if (likely(napi_mode))
+                       skb = napi_alloc_skb(&rrd_ring->napi, adapter->rx_buffer_len + 64);
+               else
+                       skb = netdev_alloc_skb(adapter->netdev, adapter->rx_buffer_len + 64);
                if (unlikely(!skb)) {
                        if (netif_msg_rx_err(adapter))
                                dev_warn(&pdev->dev, "alloc rx buffer failed\n");
                        break;
                }
 
+               if (((unsigned long)skb->data & 0xfff) == 0xfc0)
+                       skb_reserve(skb, 64);
+
                /*
                 * Make buffer alignment 2 beyond a 16 byte boundary
                 * this will result in a 16 byte aligned IP header after