[openwrt/openwrt] realtek: RTL931x: disable USXGMII SerDes setup

[LEDE Commits]

robimarko pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/c18476d0c58187238304e2300ebf341726b21413

commit c18476d0c58187238304e2300ebf341726b21413
Author: Markus Stockhausen <markus.stockhausen at gmx.de>
AuthorDate: Fri Oct 3 11:18:42 2025 -0400

    realtek: RTL931x: disable USXGMII SerDes setup
    
    The first RTL931x devices make their way into OpenWrt. Their copper
    ports are driven by different interfaces modes like 10G_QXGMII or
    Realtek proprietary XSGMII. The DSA driver has no proper handling
    for theses modes implemented yet. So a lot is auto-mapped to USXGMII
    internally. As soon as the SerDes setup activates this (wrong) mode
    the PHY connectivity breaks.
    
    Disable this mode for now and rely on the proper U-Boot setup.
    
    Signed-off-by: Markus Stockhausen <markus.stockhausen at gmx.de>
    Link: https://github.com/openwrt/openwrt/pull/20292
    Signed-off-by: Robert Marko <robimarko at gmail.com>
---
 .../linux/realtek/files-6.12/drivers/net/dsa/rtl83xx/dsa.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/target/linux/realtek/files-6.12/drivers/net/dsa/rtl83xx/dsa.c b/target/linux/realtek/files-6.12/drivers/net/dsa/rtl83xx/dsa.c
index d37a372c06..508119ff01 100644
--- a/target/linux/realtek/files-6.12/drivers/net/dsa/rtl83xx/dsa.c
+++ b/target/linux/realtek/files-6.12/drivers/net/dsa/rtl83xx/dsa.c
@@ -692,10 +692,16 @@ static void rtl931x_phylink_mac_config(struct dsa_switch *ds, int port,
 		rtl931x_sds_init(sds_num, PHY_INTERFACE_MODE_10GBASER);
 		break;
 	case PHY_INTERFACE_MODE_USXGMII:
-		/* Translates to MII_USXGMII_10GSXGMII */
-		band = rtl931x_sds_cmu_band_get(sds_num, PHY_INTERFACE_MODE_USXGMII);
-		rtl931x_sds_init(sds_num, PHY_INTERFACE_MODE_USXGMII);
-		break;
+		/*
+		 * TODO: USXGMII is currently the swiss army knife to declare 10G
+		 * multi port PHYs. Real devices use other modes instead. Especially
+		 *
+		 * - RTL8224 is driven in 10G_QXGMII
+		 * - RTL8218D/E are driven in (Realtek proprietary) XSGMII (10G SGMII)
+		 *
+		 * For now disable all USXGMII SerDes handling and rely on U-Boot setup.
+		 */
+		 break;
 	case PHY_INTERFACE_MODE_SGMII:
 		pr_info("%s setting mode PHY_INTERFACE_MODE_SGMII\n", __func__);
 		band = rtl931x_sds_cmu_band_get(sds_num, PHY_INTERFACE_MODE_SGMII);