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realtek: eth: Adapt SKB defines

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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>
This commit is contained in:
Markus Stockhausen
2026-07-21 09:30:09 +02:00
parent 419f023ec3
commit 54a7e09329
2 changed files with 19 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files
target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.c
+18 -9
View File
@@ -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,
target/linux/realtek/files-6.18/drivers/net/ethernet/rtl838x_eth.h
+1
View File
@@ -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);