[net-next,PATCH 1/2] dt-bindings: net: enetc-mdio: Document optional MDC clock

[net-next,PATCH 1/2] dt-bindings: net: enetc-mdio: Document optional MDC clock

[Marek Vasut]

Document clock from which the MDIO MDC clock are derived from.
While those clock are always present in every SoC, they are not
described in legacy DTs, make them optional. The clock-frequency
DT property is not described here, it is already part of mdio.yaml .

Signed-off-by: Marek Vasut <marex@nabladev.com>
---
Cc: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>
Cc: Clark Wang <xiaoning.wang@nxp.com>
Cc: Claudiu Manoil <claudiu.manoil@nxp.com>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: Eric Dumazet <edumazet@kernel.org>
Cc: Frank Li <Frank.Li@nxp.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Rob Herring <robh@kernel.org>
Cc: UNGLinuxDriver@microchip.com
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
Cc: Wei Fang <wei.fang@nxp.com>
Cc: devicetree@vger.kernel.org
Cc: imx@lists.linux.dev
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: netdev@vger.kernel.org
---
 Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml b/Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml
index 71c43ece82954..708d410187baa 100644
--- a/Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml
+++ b/Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml
@@ -31,6 +31,11 @@ properties:
   reg:
     maxItems: 1
 
+  clocks:
+    items:
+      - description: A reference to the input clock of the controller
+          from which the MDC frequency is derived.
+
 required:
   - compatible
   - reg
-- 
2.53.0

[net-next,PATCH 2/2] enetc: Make eMDIO MDC rate configurable from DT

[Marek Vasut]

The current eMDIO MDC rate is hard-coded in the drivers which use the
eMDIO MDC, this is not flexible for various deployments of SoCs which
use the eMDIO interface, for example i.MX95 B0 MDC clock is currently
set to 644 kHz.

Introduce enetc_mdio_priv .mdc_div field which contains the divider
used for MDC clock and pass it around, including into functions which
configure the MDC clock. This way, drivers which use the eMDIO can set
the divider as needed. Introduce enetc_mdio_update_mdc_div() function
which calculates the divider from upstream clock and clock-frequency
DT property, both of which are optional to retain compatibility with
older DTs. This is modeled according to xgmac_mdio_set_mdc_freq().

Suggested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Marek Vasut <marex@nabladev.com>
---
Cc: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>
Cc: Clark Wang <xiaoning.wang@nxp.com>
Cc: Claudiu Manoil <claudiu.manoil@nxp.com>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: Eric Dumazet <edumazet@kernel.org>
Cc: Frank Li <Frank.Li@nxp.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Rob Herring <robh@kernel.org>
Cc: UNGLinuxDriver@microchip.com
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
Cc: Wei Fang <wei.fang@nxp.com>
Cc: devicetree@vger.kernel.org
Cc: imx@lists.linux.dev
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: netdev@vger.kernel.org
---
NOTE: I could only test i.MX95 , I could not test LS or Felix
---
 drivers/net/dsa/ocelot/felix_vsc9959.c        |  5 +++
 .../net/ethernet/freescale/enetc/enetc_mdio.c | 39 ++++++++++++++++---
 .../ethernet/freescale/enetc/enetc_pci_mdio.c |  5 +++
 .../freescale/enetc/enetc_pf_common.c         | 10 +++++
 include/linux/fsl/enetc_mdio.h                |  6 +++
 5 files changed, 59 insertions(+), 6 deletions(-)

diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index 8387dd208adb9..dbeec1b229325 100644
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -1008,8 +1008,13 @@ static int vsc9959_mdio_bus_alloc(struct ocelot *ocelot)
 	 * starting with the proper offset.
 	 */
 	mdio_priv->mdio_base = 0;
+	mdio_priv->mdc_div = ENETC_MDIO_DEFAULT_DIVIDER;
 	snprintf(bus->id, MII_BUS_ID_SIZE, "%s-imdio", dev_name(dev));
 
+	rc = enetc_mdio_update_mdc_div(bus);
+	if (rc)
+		return rc;
+
 	/* Needed in order to initialize the bus mutex lock */
 	rc = mdiobus_register(bus);
 	if (rc < 0) {
diff --git a/drivers/net/ethernet/freescale/enetc/enetc_mdio.c b/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
index 998aaa394e9c4..93d61c2f1464f 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
 /* Copyright 2019 NXP */
 
+#include <linux/clk.h>
 #include <linux/fsl/enetc_mdio.h>
 #include <linux/mdio.h>
 #include <linux/of_mdio.h>
@@ -22,9 +23,9 @@
  /* external MDIO only - driven on neg MDC edge */
 #define MDIO_CFG_NEG		BIT(23)
 
-#define ENETC_EMDIO_CFG \
+#define ENETC_EMDIO_CFG(mdc_div) \
 	(MDIO_CFG_HOLD(2) | \
-	 MDIO_CFG_CLKDIV(258) | \
+	 MDIO_CFG_CLKDIV(mdc_div) | \
 	 MDIO_CFG_NEG)
 
 #define MDIO_CTL_DEV_ADDR(x)	((x) & 0x1f)
@@ -63,7 +64,7 @@ int enetc_mdio_write_c22(struct mii_bus *bus, int phy_id, int regnum,
 	u16 dev_addr;
 	int ret;
 
-	mdio_cfg = ENETC_EMDIO_CFG;
+	mdio_cfg = ENETC_EMDIO_CFG(mdio_priv->mdc_div);
 	dev_addr = regnum & 0x1f;
 	mdio_cfg &= ~MDIO_CFG_ENC45;
 
@@ -95,7 +96,7 @@ int enetc_mdio_write_c45(struct mii_bus *bus, int phy_id, int dev_addr,
 	u32 mdio_ctl, mdio_cfg;
 	int ret;
 
-	mdio_cfg = ENETC_EMDIO_CFG;
+	mdio_cfg = ENETC_EMDIO_CFG(mdio_priv->mdc_div);
 	mdio_cfg |= MDIO_CFG_ENC45;
 
 	enetc_mdio_wr(mdio_priv, ENETC_MDIO_CFG, mdio_cfg);
@@ -133,7 +134,7 @@ int enetc_mdio_read_c22(struct mii_bus *bus, int phy_id, int regnum)
 	u16 dev_addr, value;
 	int ret;
 
-	mdio_cfg = ENETC_EMDIO_CFG;
+	mdio_cfg = ENETC_EMDIO_CFG(mdio_priv->mdc_div);
 	dev_addr = regnum & 0x1f;
 	mdio_cfg &= ~MDIO_CFG_ENC45;
 
@@ -176,7 +177,7 @@ int enetc_mdio_read_c45(struct mii_bus *bus, int phy_id, int dev_addr,
 	u16 value;
 	int ret;
 
-	mdio_cfg = ENETC_EMDIO_CFG;
+	mdio_cfg = ENETC_EMDIO_CFG(mdio_priv->mdc_div);
 	mdio_cfg |= MDIO_CFG_ENC45;
 
 	enetc_mdio_wr(mdio_priv, ENETC_MDIO_CFG, mdio_cfg);
@@ -231,6 +232,32 @@ struct enetc_hw *enetc_hw_alloc(struct device *dev, void __iomem *port_regs)
 }
 EXPORT_SYMBOL_GPL(enetc_hw_alloc);
 
+int enetc_mdio_update_mdc_div(struct mii_bus *bus)
+{
+	struct enetc_mdio_priv *mdio_priv = bus->priv;
+	struct device *dev = bus->parent;
+	struct clk *enet_clk;
+	u32 div, mdc_freq;
+
+	if (device_property_read_u32(dev, "clock-frequency", &mdc_freq))
+		return 0;
+
+	enet_clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(enet_clk))
+		return dev_err_probe(dev, PTR_ERR(enet_clk),
+				     "Input clock unknown, not changing MDC frequency\n");
+
+	div = ((clk_get_rate(enet_clk) / mdc_freq) - 1) / 4;
+	if (div < 5 || div > 0x1ff)
+		return dev_err_probe(dev, -EINVAL,
+				     "Requested MDC frequency is out of range, ignoring\n");
+
+	mdio_priv->mdc_div = div;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(enetc_mdio_update_mdc_div);
+
 /* Lock for MDIO access errata on LS1028A */
 DEFINE_RWLOCK(enetc_mdio_lock);
 EXPORT_SYMBOL_GPL(enetc_mdio_lock);
diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pci_mdio.c b/drivers/net/ethernet/freescale/enetc/enetc_pci_mdio.c
index e108cac8288d3..4ff182d7d21ec 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_pci_mdio.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_pci_mdio.c
@@ -71,8 +71,13 @@ static int enetc_pci_mdio_probe(struct pci_dev *pdev,
 	mdio_priv = bus->priv;
 	mdio_priv->hw = hw;
 	mdio_priv->mdio_base = ENETC_EMDIO_BASE;
+	mdio_priv->mdc_div = ENETC_MDIO_DEFAULT_DIVIDER;
 	snprintf(bus->id, MII_BUS_ID_SIZE, "%s", dev_name(dev));
 
+	err = enetc_mdio_update_mdc_div(bus);
+	if (err)
+		return err;
+
 	pcie_flr(pdev);
 	err = pci_enable_device_mem(pdev);
 	if (err) {
diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pf_common.c b/drivers/net/ethernet/freescale/enetc/enetc_pf_common.c
index 8206884294a47..adba3fdea32dc 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_pf_common.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_pf_common.c
@@ -300,6 +300,7 @@ static int enetc_mdio_probe(struct enetc_pf *pf, struct device_node *np)
 	bus->parent = dev;
 	mdio_priv = bus->priv;
 	mdio_priv->hw = &pf->si->hw;
+	mdio_priv->mdc_div = ENETC_MDIO_DEFAULT_DIVIDER;
 
 	if (is_enetc_rev1(pf->si))
 		mdio_priv->mdio_base = ENETC_EMDIO_BASE;
@@ -308,6 +309,10 @@ static int enetc_mdio_probe(struct enetc_pf *pf, struct device_node *np)
 
 	snprintf(bus->id, MII_BUS_ID_SIZE, "%s", dev_name(dev));
 
+	err = enetc_mdio_update_mdc_div(bus);
+	if (err)
+		return err;
+
 	err = of_mdiobus_register(bus, np);
 	if (err)
 		return dev_err_probe(dev, err, "cannot register MDIO bus\n");
@@ -350,6 +355,7 @@ static int enetc_imdio_create(struct enetc_pf *pf)
 	bus->phy_mask = ~0;
 	mdio_priv = bus->priv;
 	mdio_priv->hw = &pf->si->hw;
+	mdio_priv->mdc_div = ENETC_MDIO_DEFAULT_DIVIDER;
 
 	if (is_enetc_rev1(pf->si))
 		mdio_priv->mdio_base = ENETC_PM_IMDIO_BASE;
@@ -358,6 +364,10 @@ static int enetc_imdio_create(struct enetc_pf *pf)
 
 	snprintf(bus->id, MII_BUS_ID_SIZE, "%s-imdio", dev_name(dev));
 
+	err = enetc_mdio_update_mdc_div(bus);
+	if (err)
+		return err;
+
 	err = mdiobus_register(bus);
 	if (err) {
 		dev_err(dev, "cannot register internal MDIO bus (%d)\n", err);
diff --git a/include/linux/fsl/enetc_mdio.h b/include/linux/fsl/enetc_mdio.h
index 623ccfcbf39c3..13eb6939efe29 100644
--- a/include/linux/fsl/enetc_mdio.h
+++ b/include/linux/fsl/enetc_mdio.h
@@ -6,6 +6,8 @@
 
 #include <linux/phy.h>
 
+#define ENETC_MDIO_DEFAULT_DIVIDER		258
+
 /* PCS registers */
 #define ENETC_PCS_LINK_TIMER1			0x12
 #define ENETC_PCS_LINK_TIMER1_VAL		0x06a0
@@ -33,6 +35,7 @@ struct enetc_hw;
 struct enetc_mdio_priv {
 	struct enetc_hw *hw;
 	int mdio_base;
+	int mdc_div;
 };
 
 #if IS_REACHABLE(CONFIG_FSL_ENETC_MDIO)
@@ -44,6 +47,7 @@ int enetc_mdio_read_c45(struct mii_bus *bus, int phy_id, int devad, int regnum);
 int enetc_mdio_write_c45(struct mii_bus *bus, int phy_id, int devad, int regnum,
 			 u16 value);
 struct enetc_hw *enetc_hw_alloc(struct device *dev, void __iomem *port_regs);
+int enetc_mdio_update_mdc_div(struct mii_bus *bus);
 
 #else
 
@@ -62,6 +66,8 @@ static inline int enetc_mdio_write_c45(struct mii_bus *bus, int phy_id,
 static inline struct enetc_hw *enetc_hw_alloc(struct device *dev,
 					      void __iomem *port_regs)
 { return ERR_PTR(-EINVAL); }
+static inline int enetc_mdio_update_mdc_div(struct mii_bus *bus)
+{ return -EINVAL; }
 
 #endif
 
-- 
2.53.0

Re: [net-next,PATCH 1/2] dt-bindings: net: enetc-mdio: Document optional MDC clock

[Frank Li]

On Fri, Oct 16, 2026 at 09:32:00PM +0200, Marek Vasut wrote:
> Document clock from which the MDIO MDC clock are derived from.
> While those clock are always present in every SoC, they are not
> described in legacy DTs, make them optional. The clock-frequency
> DT property is not described here, it is already part of mdio.yaml .
>
> Signed-off-by: Marek Vasut <marex@nabladev.com>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> Cc: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Andrew Lunn <andrew+netdev@lunn.ch>
> Cc: Clark Wang <xiaoning.wang@nxp.com>
> Cc: Claudiu Manoil <claudiu.manoil@nxp.com>
> Cc: Conor Dooley <conor+dt@kernel.org>
> Cc: Eric Dumazet <edumazet@kernel.org>
> Cc: Frank Li <Frank.Li@nxp.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: UNGLinuxDriver@microchip.com
> Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
> Cc: Wei Fang <wei.fang@nxp.com>
> Cc: devicetree@vger.kernel.org
> Cc: imx@lists.linux.dev
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: netdev@vger.kernel.org
> ---
>  Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml b/Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml
> index 71c43ece82954..708d410187baa 100644
> --- a/Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml
> +++ b/Documentation/devicetree/bindings/net/fsl,enetc-mdio.yaml
> @@ -31,6 +31,11 @@ properties:
>    reg:
>      maxItems: 1
>
> +  clocks:
> +    items:
> +      - description: A reference to the input clock of the controller
> +          from which the MDC frequency is derived.
> +
>  required:
>    - compatible
>    - reg
> --
> 2.53.0
>
>

Re: [net-next,PATCH 2/2] enetc: Make eMDIO MDC rate configurable from DT

[Frank Li]

On Fri, Oct 16, 2026 at 09:32:01PM +0200, Marek Vasut wrote:
> The current eMDIO MDC rate is hard-coded in the drivers which use the
> eMDIO MDC, this is not flexible for various deployments of SoCs which
> use the eMDIO interface, for example i.MX95 B0 MDC clock is currently
> set to 644 kHz.
>
> Introduce enetc_mdio_priv .mdc_div field which contains the divider
> used for MDC clock and pass it around, including into functions which
> configure the MDC clock. This way, drivers which use the eMDIO can set
> the divider as needed. Introduce enetc_mdio_update_mdc_div() function
> which calculates the divider from upstream clock and clock-frequency
> DT property, both of which are optional to retain compatibility with
> older DTs. This is modeled according to xgmac_mdio_set_mdc_freq().
>
> Suggested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> Signed-off-by: Marek Vasut <marex@nabladev.com>
> ---
> Cc: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Andrew Lunn <andrew+netdev@lunn.ch>
> Cc: Clark Wang <xiaoning.wang@nxp.com>
> Cc: Claudiu Manoil <claudiu.manoil@nxp.com>
> Cc: Conor Dooley <conor+dt@kernel.org>
> Cc: Eric Dumazet <edumazet@kernel.org>
> Cc: Frank Li <Frank.Li@nxp.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: UNGLinuxDriver@microchip.com
> Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
> Cc: Wei Fang <wei.fang@nxp.com>
> Cc: devicetree@vger.kernel.org
> Cc: imx@lists.linux.dev
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: netdev@vger.kernel.org
> ---
> NOTE: I could only test i.MX95 , I could not test LS or Felix
> ---
>  drivers/net/dsa/ocelot/felix_vsc9959.c        |  5 +++
>  .../net/ethernet/freescale/enetc/enetc_mdio.c | 39 ++++++++++++++++---
>  .../ethernet/freescale/enetc/enetc_pci_mdio.c |  5 +++
>  .../freescale/enetc/enetc_pf_common.c         | 10 +++++
>  include/linux/fsl/enetc_mdio.h                |  6 +++
>  5 files changed, 59 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
> index 8387dd208adb9..dbeec1b229325 100644
> --- a/drivers/net/dsa/ocelot/felix_vsc9959.c
> +++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
> @@ -1008,8 +1008,13 @@ static int vsc9959_mdio_bus_alloc(struct ocelot *ocelot)
>  	 * starting with the proper offset.
>  	 */
>  	mdio_priv->mdio_base = 0;
> +	mdio_priv->mdc_div = ENETC_MDIO_DEFAULT_DIVIDER;
>  	snprintf(bus->id, MII_BUS_ID_SIZE, "%s-imdio", dev_name(dev));
>
> +	rc = enetc_mdio_update_mdc_div(bus);
> +	if (rc)
> +		return rc;
> +
>  	/* Needed in order to initialize the bus mutex lock */
>  	rc = mdiobus_register(bus);
>  	if (rc < 0) {
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc_mdio.c b/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
> index 998aaa394e9c4..93d61c2f1464f 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
> @@ -1,6 +1,7 @@
>  // SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
>  /* Copyright 2019 NXP */
>
> +#include <linux/clk.h>
>  #include <linux/fsl/enetc_mdio.h>
>  #include <linux/mdio.h>
>  #include <linux/of_mdio.h>
> @@ -22,9 +23,9 @@
>   /* external MDIO only - driven on neg MDC edge */
>  #define MDIO_CFG_NEG		BIT(23)
>
> -#define ENETC_EMDIO_CFG \
> +#define ENETC_EMDIO_CFG(mdc_div) \
>  	(MDIO_CFG_HOLD(2) | \
> -	 MDIO_CFG_CLKDIV(258) | \
> +	 MDIO_CFG_CLKDIV(mdc_div) | \
>  	 MDIO_CFG_NEG)
>
>  #define MDIO_CTL_DEV_ADDR(x)	((x) & 0x1f)
> @@ -63,7 +64,7 @@ int enetc_mdio_write_c22(struct mii_bus *bus, int phy_id, int regnum,
>  	u16 dev_addr;
>  	int ret;
>
> -	mdio_cfg = ENETC_EMDIO_CFG;
> +	mdio_cfg = ENETC_EMDIO_CFG(mdio_priv->mdc_div);
>  	dev_addr = regnum & 0x1f;
>  	mdio_cfg &= ~MDIO_CFG_ENC45;
>
> @@ -95,7 +96,7 @@ int enetc_mdio_write_c45(struct mii_bus *bus, int phy_id, int dev_addr,
>  	u32 mdio_ctl, mdio_cfg;
>  	int ret;
>
> -	mdio_cfg = ENETC_EMDIO_CFG;
> +	mdio_cfg = ENETC_EMDIO_CFG(mdio_priv->mdc_div);
>  	mdio_cfg |= MDIO_CFG_ENC45;
>
>  	enetc_mdio_wr(mdio_priv, ENETC_MDIO_CFG, mdio_cfg);
> @@ -133,7 +134,7 @@ int enetc_mdio_read_c22(struct mii_bus *bus, int phy_id, int regnum)
>  	u16 dev_addr, value;
>  	int ret;
>
> -	mdio_cfg = ENETC_EMDIO_CFG;
> +	mdio_cfg = ENETC_EMDIO_CFG(mdio_priv->mdc_div);
>  	dev_addr = regnum & 0x1f;
>  	mdio_cfg &= ~MDIO_CFG_ENC45;
>
> @@ -176,7 +177,7 @@ int enetc_mdio_read_c45(struct mii_bus *bus, int phy_id, int dev_addr,
>  	u16 value;
>  	int ret;
>
> -	mdio_cfg = ENETC_EMDIO_CFG;
> +	mdio_cfg = ENETC_EMDIO_CFG(mdio_priv->mdc_div);
>  	mdio_cfg |= MDIO_CFG_ENC45;
>
>  	enetc_mdio_wr(mdio_priv, ENETC_MDIO_CFG, mdio_cfg);
> @@ -231,6 +232,32 @@ struct enetc_hw *enetc_hw_alloc(struct device *dev, void __iomem *port_regs)
>  }
>  EXPORT_SYMBOL_GPL(enetc_hw_alloc);
>
> +int enetc_mdio_update_mdc_div(struct mii_bus *bus)
> +{
> +	struct enetc_mdio_priv *mdio_priv = bus->priv;
> +	struct device *dev = bus->parent;
> +	struct clk *enet_clk;
> +	u32 div, mdc_freq;
> +
> +	if (device_property_read_u32(dev, "clock-frequency", &mdc_freq))
> +		return 0;
> +
> +	enet_clk = devm_clk_get(dev, NULL);
> +	if (IS_ERR(enet_clk))
> +		return dev_err_probe(dev, PTR_ERR(enet_clk),
> +				     "Input clock unknown, not changing MDC frequency\n");

binding said clock is optional. If return failure here, it will block
existing dts, which have not clock property.

should be devm_clk_get_optional()?

Frank