[PATCH net-next] net: dsa: microchip: enable SGMII port for KSZ9897

[PATCH net-next] net: dsa: microchip: enable SGMII port for KSZ9897

[Tapio Reijonen]

The KSZ9897 has an SGMII/1000BASE-X capable port 7, but its chip_info
entry never set .sgmii_port. As a result ksz_has_sgmii_port() is false,
ksz9477_pcs_create() is never called, and ksz9477_phylink_mac_select_pcs()
returns NULL for port 7, so no PCS is ever instantiated and a
phy-mode = "sgmii" or "1000base-x" link on that port cannot come up.

The KSZ9897 shares the KSZ9477 register layout and operations
(ksz9477_dev_ops, ksz9477_regs) and reaches its port-7 PCS through the
same SPI-indirect XPCS register window. The register-identical LAN9646
already enables this via .sgmii_port = 7. Set the same for the KSZ9897
so the XPCS instance is created and 1000BASE-X / SGMII links on port 7
negotiate correctly.

Tested on a KSZ9897 with a 1000BASE-X fibre SFP wired directly to
port 7: the link negotiates at 1Gbps/full duplex and passes traffic.

Signed-off-by: Tapio Reijonen <tapio.reijonen@vaisala.com>
---
 drivers/net/dsa/microchip/ksz_common.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index d1726778bb488e424aed450fb02c8fe4b332a1f4..718c72206ab451cb4c5e88fc91a5eae4892518b7 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -1591,6 +1591,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.internal_phy	= {true, true, true, true,
 				   true, false, false},
 		.gbit_capable	= {true, true, true, true, true, true, true},
+		.sgmii_port = 7,
 	},
 
 	[KSZ9893] = {

---
base-commit: 322008f87f917e2217eeac386a9410945092eb2e
change-id: 20260703-ksz9897-sgmii-port-48ddb100e015

Best regards,
-- 
Tapio Reijonen <tapio.reijonen@vaisala.com>

Re: [PATCH net-next] net: dsa: microchip: enable SGMII port for KSZ9897

[Jakub Kicinski]

On Fri, 03 Jul 2026 06:37:28 +0000 Tapio Reijonen wrote:
> The KSZ9897 has an SGMII/1000BASE-X capable port 7, but its chip_info
> entry never set .sgmii_port. As a result ksz_has_sgmii_port() is false,
> ksz9477_pcs_create() is never called, and ksz9477_phylink_mac_select_pcs()
> returns NULL for port 7, so no PCS is ever instantiated and a
> phy-mode = "sgmii" or "1000base-x" link on that port cannot come up.

The netdev patch queue has overflown, if this patch is necessary you
will have to repost it.