[openwrt/openwrt] realtek: eth: use free floating rings for RTL838x

[LEDE Commits]

robimarko pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/b2c56b52334ec9d81d57fd4449feda2d09083679

commit b2c56b52334ec9d81d57fd4449feda2d09083679
Author: Markus Stockhausen <markus.stockhausen at gmx.de>
AuthorDate: Tue Feb 3 08:15:33 2026 +0100

    realtek: eth: use free floating rings for RTL838x
    
    The ring counters on RTL83xx allow a space of up to 15 entries.
    But rings can be filled faster than data is received and might be
    much larger defined (128 at the moment). Also NAPI processing
    allows much more than 15 packets to be processed in one chunk.
    Disable the counters and let the hardware automatically detect
    the available buffers by the ownership flag. With this disable
    a pseudo workaround that tried to mitigate the buffer filling
    on RTL838x due to wrong setup.
    
    Remark. This commit fixes several inconsistencies in the setup
    code. RTL838x runs the setup twice with different values. RTL839x
    does not run the setup at all.
    
    Signed-off-by: Markus Stockhausen <markus.stockhausen at gmx.de>
    Link: https://github.com/openwrt/openwrt/pull/21856
    Signed-off-by: Robert Marko <robimarko at gmail.com>
---
 .../files-6.12/drivers/net/ethernet/rtl838x_eth.c  | 38 +++++-----------------
 1 file changed, 9 insertions(+), 29 deletions(-)

diff --git a/target/linux/realtek/files-6.12/drivers/net/ethernet/rtl838x_eth.c b/target/linux/realtek/files-6.12/drivers/net/ethernet/rtl838x_eth.c
index d27c750152..529658121f 100644
--- a/target/linux/realtek/files-6.12/drivers/net/ethernet/rtl838x_eth.c
+++ b/target/linux/realtek/files-6.12/drivers/net/ethernet/rtl838x_eth.c
@@ -217,14 +217,9 @@ struct rteth_ctrl {
  * When the content reaches the ring size, the ASIC no longer adds
  * packets to this receive queue.
  */
-static void rteth_838x_update_counter(int r, int released)
+static void rteth_83xx_update_counter(int r, int released)
 {
-	/* This feature is not available on RTL838x SoCs */
-}
-
-static void rteth_839x_update_counter(int r, int released)
-{
-	/* This feature is not available on RTL839x SoCs */
+	/* Free floating rings without space tracking */
 }
 
 static void rteth_930x_update_counter(int r, int released)
@@ -479,8 +474,8 @@ static void rteth_838x_hw_reset(struct rteth_ctrl *ctrl)
 
 	rteth_nic_reset(ctrl, 0xc);
 
-	/* Setup Head of Line */
-	sw_w32(0, RTL838X_DMA_IF_RX_RING_SIZE);  /* Disabled on RTL8380 */
+	/* Free floating rings without space tracking */
+	sw_w32(0, RTL838X_DMA_IF_RX_RING_SIZE);
 }
 
 static void rteth_839x_hw_reset(struct rteth_ctrl *ctrl)
@@ -501,9 +496,6 @@ static void rteth_839x_hw_reset(struct rteth_ctrl *ctrl)
 
 	rteth_nic_reset(ctrl, 0xc);
 
-	/* Setup Head of Line */
-	sw_w32(0xffffffff, RTL839X_DMA_IF_RX_RING_CNTR);
-
 	/* Re-enable link change interrupt */
 	sw_w32(0xffffffff, RTL839X_ISR_PORT_LINK_STS_CHG);
 	sw_w32(0xffffffff, RTL839X_ISR_PORT_LINK_STS_CHG + 4);
@@ -513,6 +505,9 @@ static void rteth_839x_hw_reset(struct rteth_ctrl *ctrl)
 	/* Restore notification settings: on RTL838x these bits are null */
 	sw_w32_mask(7 << 20, int_saved & (7 << 20), ctrl->r->dma_if_intr_msk);
 	sw_w32(nbuf, RTL839X_DMA_IF_NBUF_BASE_DESC_ADDR_CTRL);
+
+	/* Free floating rings without space tracking */
+	sw_w32(0, RTL839X_DMA_IF_RX_RING_SIZE);
 }
 
 static void rteth_93xx_hw_reset(struct rteth_ctrl *ctrl)
@@ -551,9 +546,6 @@ static void rteth_hw_ring_setup(struct rteth_ctrl *ctrl)
 
 static void rtl838x_hw_en_rxtx(struct rteth_ctrl *ctrl)
 {
-	/* Disable Head of Line features for all RX rings */
-	sw_w32(0xffffffff, ctrl->r->dma_if_rx_ring_size(0));
-
 	/* Truncate RX buffer to DEFAULT_MTU bytes, pad TX */
 	sw_w32((DEFAULT_MTU << 16) | RX_TRUNCATE_EN_83XX | TX_PAD_EN_838X, ctrl->r->dma_if_ctrl);
 
@@ -1077,18 +1069,6 @@ static int rtl838x_hw_receive(struct net_device *dev, int r, int budget)
 
 		skb = netdev_alloc_skb_ip_align(dev, len);
 		if (likely(skb)) {
-			/* BUG: Prevent bug on RTL838x SoCs */
-			if (ctrl->r->family_id == RTL8380_FAMILY_ID) {
-				sw_w32(0xffffffff, ctrl->r->dma_if_rx_ring_size(0));
-				for (int i = 0; i < ctrl->rxrings; i++) {
-					unsigned int val;
-
-					/* Update each ring cnt */
-					val = sw_r32(ctrl->r->dma_if_rx_ring_cntr(i));
-					sw_w32(val, ctrl->r->dma_if_rx_ring_cntr(i));
-				}
-			}
-
 			/* Make sure data is visible */
 			mb();
 			skb_put_data(skb, (u8 *)KSEG1ADDR(data), len);
@@ -1473,7 +1453,7 @@ static const struct rteth_config rteth_838x_cfg = {
 	.get_mac_tx_pause_sts = rtl838x_get_mac_tx_pause_sts,
 	.mac = RTL838X_MAC,
 	.l2_tbl_flush_ctrl = RTL838X_L2_TBL_FLUSH_CTRL,
-	.update_counter = rteth_838x_update_counter,
+	.update_counter = rteth_83xx_update_counter,
 	.create_tx_header = rteth_838x_create_tx_header,
 	.decode_tag = rteth_838x_decode_tag,
 	.hw_reset = &rteth_838x_hw_reset,
@@ -1517,7 +1497,7 @@ static const struct rteth_config rteth_839x_cfg = {
 	.get_mac_tx_pause_sts = rtl839x_get_mac_tx_pause_sts,
 	.mac = RTL839X_MAC,
 	.l2_tbl_flush_ctrl = RTL839X_L2_TBL_FLUSH_CTRL,
-	.update_counter = rteth_839x_update_counter,
+	.update_counter = rteth_83xx_update_counter,
 	.create_tx_header = rteth_839x_create_tx_header,
 	.decode_tag = rteth_839x_decode_tag,
 	.hw_reset = &rteth_839x_hw_reset,