[PATCH net-next 3/4] net: phy: realtek: use paged access for MDIO_MMD_VEND2 in C22 mode
From: Daniel Golle
Date: Sun Jan 04 2026 - 08:12:55 EST
RTL822x cannot access MDIO_MMD_VEND2 via MII_MMD_CTRL/MII_MMD_DATA.
A mapping to use paged access needs to be used instead.
All other MMD devices can be accessed as usual.
Implement phy_read_mmd and phy_write_mmd using paged access for
MDIO_MMD_VEND2 in Clause-22 mode instead of relying on
MII_MMD_CTRL/MII_MMD_DATA.
This allows eg. rtl822x_config_aneg to work as expected in case the
MDIO bus doesn't support Clause-45 access.
Suggested-by: Bevan Weiss <bevan.weiss@xxxxxxxxx>
Signed-off-by: Daniel Golle <daniel@xxxxxxxxxxxxxx>
---
drivers/net/phy/realtek/realtek_main.c | 116 ++++++++++++++++++++++++-
1 file changed, 113 insertions(+), 3 deletions(-)
diff --git a/drivers/net/phy/realtek/realtek_main.c b/drivers/net/phy/realtek/realtek_main.c
index 0653a9d8fcb6f..142a5421fe84c 100644
--- a/drivers/net/phy/realtek/realtek_main.c
+++ b/drivers/net/phy/realtek/realtek_main.c
@@ -140,9 +140,8 @@
#define RTL822X_VND1_SERDES_INBAND_ENABLE 0x70d0
#define RTL822X_VND1_SERDES_DATA 0x7589
-/* RTL822X_VND2_XXXXX registers are only accessible when phydev->is_c45
- * is set, they cannot be accessed by C45-over-C22.
- */
+#define RTL822X_VND2_TO_PAGE(reg) ((reg) >> 4)
+#define RTL822X_VND2_TO_PAGE_REG(reg) (16 + (((reg) & GENMASK(3, 0)) >> 1))
#define RTL822X_VND2_C22_REG(reg) (0xa400 + 2 * (reg))
#define RTL8221B_VND2_INER 0xa4d2
@@ -1247,6 +1246,105 @@ static int rtl822x_probe(struct phy_device *phydev)
return 0;
}
+/* RTL822x cannot access MDIO_MMD_VEND2 via MII_MMD_CTRL/MII_MMD_DATA.
+ * A mapping to use paged access needs to be used instead.
+ * All other MMD devices can be accessed as usual.
+ */
+static int rtl822xb_read_mmd(struct phy_device *phydev, int devnum, u16 reg)
+{
+ int oldpage, ret, read_ret;
+ u16 page;
+
+ /* Use Clause-45 bus access in case it is available */
+ if (phydev->is_c45)
+ return __mdiobus_c45_read(phydev->mdio.bus, phydev->mdio.addr,
+ devnum, mmdreg);
+
+ /* Use indirect access via MII_MMD_CTRL and MII_MMD_DATA for all
+ * MMDs except MDIO_MMD_VEND2
+ */
+ if (devnum != MDIO_MMD_VEND2) {
+ __mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
+ MII_MMD_CTRL, devnum);
+ __mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
+ MII_MMD_DATA, mmdreg);
+ __mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
+ MII_MMD_CTRL, devnum | MII_MMD_CTRL_NOINCR);
+
+ return __mdiobus_read(phydev->mdio.bus, phydev->mdio.addr,
+ MII_MMD_DATA);
+ }
+
+ /* Use paged access for MDIO_MMD_VEND2 over Clause-22 */
+ page = RTL822X_VND2_TO_PAGE(reg);
+ oldpage = __phy_read(phydev, RTL821x_PAGE_SELECT);
+ if (oldpage < 0)
+ return ret;
+
+ if (oldpage != page) {
+ ret = __phy_write(phydev, RTL821x_PAGE_SELECT, page);
+ if (ret < 0)
+ return ret;
+ }
+
+ read_ret = __phy_read(phydev, RTL822X_VND2_TO_PAGE_REG(reg));
+ if (oldpage != page) {
+ ret = __phy_write(phydev, RTL821x_PAGE_SELECT, oldpage);
+ if (ret < 0)
+ return ret;
+ }
+
+ return read_ret;
+}
+
+static int rtl822xb_write_mmd(struct phy_device *phydev, int devnum, u16 reg,
+ u16 val)
+{
+ int oldpage, ret, write_ret;
+ u16 page;
+
+ /* Use Clause-45 bus access in case it is available */
+ if (phydev->is_c45)
+ return __mdiobus_c45_write(phydev->mdio.bus, phydev->mdio.addr,
+ devnum, mmdreg, val);
+
+ /* Use indirect access via MII_MMD_CTRL and MII_MMD_DATA for all
+ * MMDs except MDIO_MMD_VEND2
+ */
+ if (devnum != MDIO_MMD_VEND2) {
+ __mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
+ MII_MMD_CTRL, devnum);
+ __mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
+ MII_MMD_DATA, mmdreg);
+ __mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
+ MII_MMD_CTRL, devnum | MII_MMD_CTRL_NOINCR);
+
+ return __mdiobus_write(phydev->mdio.bus, phydev->mdio.addr,
+ MII_MMD_DATA, val);
+ }
+
+ /* Use paged access for MDIO_MMD_VEND2 over Clause-22 */
+ page = RTL822X_VND2_TO_PAGE(reg);
+ oldpage = __phy_read(phydev, RTL821x_PAGE_SELECT);
+ if (oldpage < 0)
+ return ret;
+
+ if (oldpage != page) {
+ ret = __phy_write(phydev, RTL821x_PAGE_SELECT, page);
+ if (ret < 0)
+ return ret;
+ }
+
+ write_ret = __phy_write(phydev, RTL822X_VND2_TO_PAGE_REG(reg), val);
+ if (oldpage != page) {
+ ret = __phy_write(phydev, RTL821x_PAGE_SELECT, oldpage);
+ if (ret < 0)
+ return ret;
+ }
+
+ return write_ret;
+}
+
static int rtl822x_set_serdes_option_mode(struct phy_device *phydev, bool gen1)
{
bool has_2500, has_sgmii;
@@ -2150,6 +2248,8 @@ static struct phy_driver realtek_drvs[] = {
.resume = rtlgen_resume,
.read_page = rtl821x_read_page,
.write_page = rtl821x_write_page,
+ .read_mmd = rtl822xb_read_mmd,
+ .write_mmd = rtl822xb_write_mmd,
}, {
.match_phy_device = rtl8221b_match_phy_device,
.name = "RTL8226B_RTL8221B 2.5Gbps PHY",
@@ -2164,6 +2264,8 @@ static struct phy_driver realtek_drvs[] = {
.resume = rtlgen_resume,
.read_page = rtl821x_read_page,
.write_page = rtl821x_write_page,
+ .read_mmd = rtl822xb_read_mmd,
+ .write_mmd = rtl822xb_write_mmd,
}, {
PHY_ID_MATCH_EXACT(0x001cc838),
.name = "RTL8226-CG 2.5Gbps PHY",
@@ -2176,6 +2278,8 @@ static struct phy_driver realtek_drvs[] = {
.read_status = rtl822xb_c45_read_status,
.suspend = genphy_c45_pma_suspend,
.resume = rtlgen_c45_resume,
+ .read_mmd = rtl822xb_read_mmd,
+ .write_mmd = rtl822xb_write_mmd,
}, {
PHY_ID_MATCH_EXACT(0x001cc848),
.name = "RTL8226B-CG_RTL8221B-CG 2.5Gbps PHY",
@@ -2190,6 +2294,8 @@ static struct phy_driver realtek_drvs[] = {
.resume = rtlgen_resume,
.read_page = rtl821x_read_page,
.write_page = rtl821x_write_page,
+ .read_mmd = rtl822xb_read_mmd,
+ .write_mmd = rtl822xb_write_mmd,
}, {
.match_phy_device = rtl8221b_vb_cg_c22_match_phy_device,
.name = "RTL8221B-VB-CG 2.5Gbps PHY (C22)",
@@ -2205,6 +2311,8 @@ static struct phy_driver realtek_drvs[] = {
.resume = rtlgen_resume,
.read_page = rtl821x_read_page,
.write_page = rtl821x_write_page,
+ .read_mmd = rtl822xb_read_mmd,
+ .write_mmd = rtl822xb_write_mmd,
}, {
.match_phy_device = rtl8221b_vb_cg_c45_match_phy_device,
.name = "RTL8221B-VB-CG 2.5Gbps PHY (C45)",
@@ -2235,6 +2343,8 @@ static struct phy_driver realtek_drvs[] = {
.resume = rtlgen_resume,
.read_page = rtl821x_read_page,
.write_page = rtl821x_write_page,
+ .read_mmd = rtl822xb_read_mmd,
+ .write_mmd = rtl822xb_write_mmd,
}, {
.match_phy_device = rtl8221b_vm_cg_c45_match_phy_device,
.name = "RTL8221B-VM-CG 2.5Gbps PHY (C45)",
--
2.52.0