netdev - [net-next PATCH v2 03/11] net: phy: Fix PMA identifier handling in XPCS

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Message-ID: 
 <176218921797.2759873.4522051915422366242.stgit@ahduyck-xeon-server.home.arpa>
Date: Mon, 03 Nov 2025 09:00:17 -0800
From: Alexander Duyck <alexander.duyck@...il.com>
To: netdev@...r.kernel.org
Cc: kuba@...nel.org, kernel-team@...a.com, andrew+netdev@...n.ch,
 hkallweit1@...il.com, linux@...linux.org.uk, pabeni@...hat.com,
 davem@...emloft.net
Subject: [net-next PATCH v2 03/11] net: phy: Fix PMA identifier handling in
 XPCS

From: Alexander Duyck <alexanderduyck@...com>

The XPCS driver was mangling the PMA identifier as the original code
appears to have been focused on just capturing the OUI. Rather than store a
mangled ID it is better to work with the actual PMA ID and instead just
mask out the values that don't apply rather than shifting them and
reordering them as you still don't get the original OUI for the NIC without
having to bitswap the values as per the definition of the layout in IEEE
802.3-2022 22.2.4.3.1.

By laying it out as it was in the hardware it is also less likely for us to
have an unintentional collision as the enum values will occupy the revision
number area while the OUI occupies the upper 22 bits.

Signed-off-by: Alexander Duyck <alexanderduyck@...com>
---
 drivers/net/pcs/pcs-xpcs.c   |    9 ++++-----
 include/linux/pcs/pcs-xpcs.h |    2 +-
 include/uapi/linux/mdio.h    |    5 +++++
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index f2a6fdb972e7..fde9d9299756 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -1328,17 +1328,16 @@ static int xpcs_read_ids(struct dw_xpcs *xpcs)
 	if (ret < 0)
 		return ret;
 
-	id = ret;
+	id = ret << 16;
 
 	ret = xpcs_read(xpcs, MDIO_MMD_PMAPMD, MDIO_DEVID2);
 	if (ret < 0)
 		return ret;
 
-	/* Note the inverted dword order and masked out Model/Revision numbers
-	 * with respect to what is done with the PCS ID...
+	/* For now we only record the OUI for the PMAPMD, we may want to
+	 * add the model number at some point in the future.
 	 */
-	ret = (ret >> 10) & 0x3F;
-	id |= ret << 16;
+	id |= ret & MDIO_DEVID2_OUI;
 
 	/* Set the PMA ID if it hasn't been pre-initialized */
 	if (xpcs->info.pma == DW_XPCS_PMA_ID_NATIVE)
diff --git a/include/linux/pcs/pcs-xpcs.h b/include/linux/pcs/pcs-xpcs.h
index e40f554ff717..4cf6bd611e5a 100644
--- a/include/linux/pcs/pcs-xpcs.h
+++ b/include/linux/pcs/pcs-xpcs.h
@@ -38,7 +38,7 @@ enum dw_xpcs_pma_id {
 	DW_XPCS_PMA_GEN4_6G_ID,
 	DW_XPCS_PMA_GEN5_10G_ID,
 	DW_XPCS_PMA_GEN5_12G_ID,
-	WX_TXGBE_XPCS_PMA_10G_ID = 0x0018fc80,
+	WX_TXGBE_XPCS_PMA_10G_ID = 0xfc806000,
 };
 
 struct dw_xpcs_info {
diff --git a/include/uapi/linux/mdio.h b/include/uapi/linux/mdio.h
index eee38690ddc4..387c8b4eeb61 100644
--- a/include/uapi/linux/mdio.h
+++ b/include/uapi/linux/mdio.h
@@ -139,6 +139,11 @@
 #define MDIO_AN_STAT1_PAGE		0x0040	/* Page received */
 #define MDIO_AN_STAT1_XNP		0x0080	/* Extended next page status */
 
+/* Device Identifier 2 */
+#define MDIO_DEVID2_OUI			0xfc00	/* OUI Portion of PHY ID */
+#define MDIO_DEVID2_MODEL_NUM		0x03f0	/* Manufacturer's Model Number */
+#define MDIO_DEVID2_REV_NUM		0x000f	/* Revision Number */
+
 /* Speed register. */
 #define MDIO_SPEED_10G			0x0001	/* 10G capable */
 #define MDIO_PMA_SPEED_2B		0x0002	/* 2BASE-TL capable */