realtek: eth: Adapt SKB defines

Testing shows that the existing performance boost by aligning the data
to 2 bytes (NET_IP_ALIGN) breaks fragment handling on RTL838x devices. The
SoC silently drops 2 bytes between each fragment. Use this tricky alignment
only when it is supported. This will bring down performance on RTL838x SoCs
by 30%. All other SoCs are unaffected. This is a legitimate tradeoff for
allowing multiple fragments. While we are here make clearer what the
definies are about and rename them to a SKB_ prefix.

Link: https://github.com/openwrt/openwrt/pull/24245
Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>

diff --git a/target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.c b/target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.c
index c8591541e319a2fbc5d2eca60f32aa7e2f1dab52..b955219c92874a9953cb134f04f5744f335f78ef 100644 (file)
--- a/target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.c
+++ b/target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.c
@@ -30,7 +30,6 @@
 #define RING_OWN_HW                    BIT(0)
 #define RING_WRAP                      BIT(1)
 
-#define RTETH_SKB_HEADROOM             (NET_SKB_PAD + NET_IP_ALIGN)
 #define RTETH_RX_RING_SIZE             128
 #define RTETH_RX_RINGS                 2
 #define RTETH_TX_RING_SIZE             16
@@ -42,7 +41,11 @@
 #define RX_TRUNCATE_EN_93XX            BIT(6)
 #define RX_TRUNCATE_EN_83XX            BIT(4)
 #define TX_PAD_EN_838X                 BIT(5)
-#define RING_BUFFER                    1600
+
+#define SKB_FRAG_SIZE                  1600
+#define SKB_PAD                                MAX(32, L1_CACHE_BYTES)
+#define SKB_HEADROOM_FAST              (SKB_PAD + NET_IP_ALIGN)
+#define SKB_HEADROOM_SLOW              SKB_PAD
 
 /* Define page pool that holds 2KB fragments in 4KB pages and has 8 safety pages */
 #define PPOOL_FRAG_SIZE                        2048
@@ -668,7 +671,7 @@ static int rteth_setup_ring_buffer(struct rteth_ctrl *ctrl)
         * and the DMA capabilities of the network adapter. Be defensive and add some checks to
         * assist further error analysis.
         */
-       BUILD_BUG_ON(RTETH_SKB_HEADROOM + RING_BUFFER +
+       BUILD_BUG_ON(SKB_HEADROOM_FAST + SKB_FRAG_SIZE +
                     SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) > PPOOL_FRAG_SIZE);
 
        for (int r = 0; r < RTETH_RX_RINGS; r++) {
@@ -686,8 +689,9 @@ static int rteth_setup_ring_buffer(struct rteth_ctrl *ctrl)
                        highmem |= PageHighMem(page);
                        paddr = max(paddr, page_to_phys(page));
 
-                       packet->size = RING_BUFFER;
-                       packet->dma = page_pool_get_dma_addr(page) + RTETH_SKB_HEADROOM + offset;
+                       packet->size = SKB_FRAG_SIZE;
+                       packet->dma = page_pool_get_dma_addr(page)
+                                   + ctrl->r->skb_headroom + offset;
                        packet->page = page;
                        packet->page_offset = offset;
                        ctrl->rx_data[r].ring[i] = ctrl->rx_data_dma +
@@ -1126,7 +1130,7 @@ static int rteth_hw_receive(struct net_device *dev, int ring, int budget)
                packet = &ctrl->rx_data[ring].packet[slot];
                len = packet->len - ETH_FCS_LEN;
 
-               if (unlikely(len > RING_BUFFER)) {
+               if (unlikely(len > SKB_FRAG_SIZE)) {
                        netdev_err(dev, "invalid packet with %d bytes received\n", len);
                        dev->stats.rx_errors++;
                        goto recycle;
@@ -1144,10 +1148,11 @@ static int rteth_hw_receive(struct net_device *dev, int ring, int budget)
 
                packet->page = new_page;
                packet->page_offset = new_offset;
-               packet->dma = page_pool_get_dma_addr(new_page) + new_offset + RTETH_SKB_HEADROOM;
+               packet->dma = page_pool_get_dma_addr(new_page)
+                           + new_offset + ctrl->r->skb_headroom;
 
                page_pool_dma_sync_for_cpu(ctrl->rx_qs[ring].page_pool, old_page,
-                                          old_offset + RTETH_SKB_HEADROOM, len);
+                                          old_offset + ctrl->r->skb_headroom, len);
 
                skb = napi_build_skb(page_address(old_page) + old_offset, PPOOL_FRAG_SIZE);
                if (unlikely(!skb)) {
@@ -1156,7 +1161,7 @@ static int rteth_hw_receive(struct net_device *dev, int ring, int budget)
                        goto recycle;
                }
 
-               skb_reserve(skb, RTETH_SKB_HEADROOM);
+               skb_reserve(skb, ctrl->r->skb_headroom);
                skb_mark_for_recycle(skb);
                skb_put(skb, len);
 
@@ -1448,6 +1453,7 @@ static const struct rteth_config rteth_838x_cfg = {
        .dma_tx_base = RTETH_838X_DMA_TX_BASE,
        .mac_force_mode_ctrl = RTETH_838X_MAC_FORCE_MODE_CTRL,
        .rst_glb_ctrl = RTL838X_RST_GLB_CTRL_0,
+       .skb_headroom = SKB_HEADROOM_SLOW,
        .mac_reg = { RTETH_838X_MAC_ADDR_CTRL,
                     RTETH_838X_MAC_ADDR_CTRL_ALE,
                     RTETH_838X_MAC_ADDR_CTRL_MAC },
@@ -1494,6 +1500,7 @@ static const struct rteth_config rteth_839x_cfg = {
        .dma_tx_base = RTETH_839X_DMA_TX_BASE,
        .mac_force_mode_ctrl = RTETH_839X_MAC_FORCE_MODE_CTRL,
        .rst_glb_ctrl = RTL839X_RST_GLB_CTRL,
+       .skb_headroom = SKB_HEADROOM_FAST,
        .mac_reg = { RTETH_839X_MAC_ADDR_CTRL },
        .l2_tbl_flush_ctrl = RTL839X_L2_TBL_FLUSH_CTRL,
        .update_counter = rteth_83xx_update_counter,
@@ -1540,6 +1547,7 @@ static const struct rteth_config rteth_930x_cfg = {
        .l2_ntfy_if_intr_msk = RTL930X_L2_NTFY_IF_INTR_MSK,
        .mac_force_mode_ctrl = RTETH_930X_MAC_FORCE_MODE_CTRL,
        .rst_glb_ctrl = RTL930X_RST_GLB_CTRL_0,
+       .skb_headroom = SKB_HEADROOM_FAST,
        .mac_reg = { RTETH_930X_MAC_L2_ADDR_CTRL },
        .l2_tbl_flush_ctrl = RTL930X_L2_TBL_FLUSH_CTRL,
        .update_counter = rteth_93xx_update_counter,
@@ -1585,6 +1593,7 @@ static const struct rteth_config rteth_931x_cfg = {
        .l2_ntfy_if_intr_msk = RTL931X_L2_NTFY_IF_INTR_MSK,
        .mac_force_mode_ctrl = RTETH_931X_MAC_FORCE_MODE_CTRL,
        .rst_glb_ctrl = RTL931X_RST_GLB_CTRL,
+       .skb_headroom = SKB_HEADROOM_FAST,
        .mac_reg = { RTETH_930X_MAC_L2_ADDR_CTRL },
        .l2_tbl_flush_ctrl = RTL931X_L2_TBL_FLUSH_CTRL,
        .update_counter = rteth_93xx_update_counter,

diff --git a/target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.h b/target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.h
index 36ba386dd3f670933f9c6a2a2fd843e17b33dd36..9d6837e915bfc8dbc7fd1a7cb70c33802e0971f3 100644 (file)
--- a/target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.h
+++ b/target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.h
@@ -209,6 +209,7 @@ struct rteth_config {
        int dma_rx_base;
        int dma_tx_base;
        int rst_glb_ctrl;
+       int skb_headroom;
        u32 mac_reg[RTETH_MAX_MAC_REGS];
        int l2_tbl_flush_ctrl;
        void (*create_tx_header)(struct rteth_packet *h, unsigned int dest_port, int prio);