[PATCH net-next v2 0/5] Side MDIO Support for LAN937x Switches

[PATCH net-next v2 0/5] Side MDIO Support for LAN937x Switches

[Oleksij Rempel]

This patch set introduces support for an internal MDIO bus in LAN937x
switches, enabling the use of a side MDIO channel for PHY management
while keeping SPI as the main interface for switch configuration.

changelogs are added to separate patches.

Oleksij Rempel (5):
  dt-bindings: net: dsa: ksz: add internal MDIO bus description
  dt-bindings: net: dsa: ksz: add mdio-parent-bus property for internal
    MDIO
  net: dsa: microchip: Refactor MDIO handling for side MDIO access
  net: dsa: microchip: cleanup error handling in ksz_mdio_register
  net: dsa: microchip: add support for side MDIO interface in LAN937x

 .../bindings/net/dsa/microchip,ksz.yaml       |  20 ++
 drivers/net/dsa/microchip/ksz_common.c        | 192 +++++++++++++--
 drivers/net/dsa/microchip/ksz_common.h        |  59 +++++
 drivers/net/dsa/microchip/lan937x.h           |   2 +
 drivers/net/dsa/microchip/lan937x_main.c      | 226 ++++++++++++++++--
 drivers/net/dsa/microchip/lan937x_reg.h       |   4 +
 6 files changed, 471 insertions(+), 32 deletions(-)

--
2.39.5

[PATCH net-next v2 1/5] dt-bindings: net: dsa: ksz: add internal MDIO bus description

[Oleksij Rempel]

Add description for the internal MDIO bus, including integrated PHY
nodes, to ksz DSA bindings.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
 .../devicetree/bindings/net/dsa/microchip,ksz.yaml    | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
index 30c0c3e6f37a4..a4e463819d4d7 100644
--- a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
+++ b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
@@ -81,6 +81,17 @@ properties:
   interrupts:
     maxItems: 1
 
+  mdio:
+    $ref: /schemas/net/mdio.yaml#
+    unevaluatedProperties: false
+    patternProperties:
+      "^ethernet-phy@[0-9a-f]$":
+        type: object
+        $ref: /schemas/net/ethernet-phy.yaml#
+        unevaluatedProperties: false
+        description:
+          Integrated PHY node
+
 required:
   - compatible
   - reg
-- 
2.39.5

[PATCH net-next v2 2/5] dt-bindings: net: dsa: ksz: add mdio-parent-bus property for internal MDIO

[Oleksij Rempel]

Introduce `mdio-parent-bus` property in the ksz DSA bindings to
reference the parent MDIO bus when the internal MDIO bus is attached to
it, bypassing the main management interface.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
 .../devicetree/bindings/net/dsa/microchip,ksz.yaml       | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
index a4e463819d4d7..121a4bbd147be 100644
--- a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
+++ b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
@@ -84,6 +84,15 @@ properties:
   mdio:
     $ref: /schemas/net/mdio.yaml#
     unevaluatedProperties: false
+    properties:
+      mdio-parent-bus:
+        $ref: /schemas/types.yaml#/definitions/phandle
+        description:
+          Phandle pointing to the MDIO bus controller connected to the
+          secondary MDIO interface. This property should be used when
+          the internal MDIO bus is accessed via a secondary MDIO
+          interface rather than the primary management interface.
+
     patternProperties:
       "^ethernet-phy@[0-9a-f]$":
         type: object
-- 
2.39.5

Re: [PATCH net-next v2 2/5] dt-bindings: net: dsa: ksz: add mdio-parent-bus property for internal MDIO

[Vladimir Oltean]

On Tue, Oct 29, 2024 at 12:07:29PM +0100, Oleksij Rempel wrote:
> Introduce `mdio-parent-bus` property in the ksz DSA bindings to
> reference the parent MDIO bus when the internal MDIO bus is attached to
> it, bypassing the main management interface.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> ---
>  .../devicetree/bindings/net/dsa/microchip,ksz.yaml       | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
> index a4e463819d4d7..121a4bbd147be 100644
> --- a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
> +++ b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
> @@ -84,6 +84,15 @@ properties:
>    mdio:
>      $ref: /schemas/net/mdio.yaml#
>      unevaluatedProperties: false
> +    properties:
> +      mdio-parent-bus:
> +        $ref: /schemas/types.yaml#/definitions/phandle
> +        description:
> +          Phandle pointing to the MDIO bus controller connected to the
> +          secondary MDIO interface. This property should be used when
> +          the internal MDIO bus is accessed via a secondary MDIO
> +          interface rather than the primary management interface.
> +
>      patternProperties:
>        "^ethernet-phy@[0-9a-f]$":
>          type: object
> -- 
> 2.39.5
> 

I'm not saying whether this is good or bad, I'm just worried about
mixing quantities having different measurement units into the same
address space.

Just like in the case of an mdio-mux, there is no address space isolation
between the parent bus and the child bus. AKA you can't have this,
because there would be clashes:

	host_bus: mdio@abcd {
		ethernet-phy@2 {
			reg = <2>;
		};
	};

	child_bus: mdio@efgh {
		mdio-parent-bus = <&host_bus>;

		ethernet-phy@2 {
			reg = <2>;
		};
	};

But there is a big difference. With an mdio-mux, you could statically
detect address space clashes by inspecting the PHY addresses on the 2
buses. But with the lan937x child MDIO bus, in this design, you can't,
because the "reg" values don't represent MDIO addresses, but switch port
numbers (this is kind of important, but I don't see it mentioned in the
dt-binding). These are translated by lan937x_create_phy_addr_map() using
the CASCADE_ID/VPHY_ADD pin strapping information read over SPI.
I.e. with the same device tree, you may or may not have address space
clashes depending on pin strapping. No way to tell.

Have you considered putting the switch's internal PHYs directly under
the host MDIO bus node, with their 'real' MDIO bus computed statically
by the DT writer based on the pin straps? Yes, I'm aware that this means
different pin straps mean different device trees.

Under certain circumstances I could understand this dt-binding design
with an mdio-parent-bus, like for example if the MDIO addresses at which
the internal PHYs respond would be configurable over SPI, from the switch
registers. But I'm not led to believe that here, this is the case.

Re: [PATCH net-next v2 2/5] dt-bindings: net: dsa: ksz: add mdio-parent-bus property for internal MDIO

[Oleksij Rempel]

On Tue, Oct 29, 2024 at 02:31:07PM +0200, Vladimir Oltean wrote:
> On Tue, Oct 29, 2024 at 12:07:29PM +0100, Oleksij Rempel wrote:
> > Introduce `mdio-parent-bus` property in the ksz DSA bindings to
> > reference the parent MDIO bus when the internal MDIO bus is attached to
> > it, bypassing the main management interface.
> > 
> > Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> > Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
> > Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> > ---
> >  .../devicetree/bindings/net/dsa/microchip,ksz.yaml       | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
> > index a4e463819d4d7..121a4bbd147be 100644
> > --- a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
> > +++ b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
> > @@ -84,6 +84,15 @@ properties:
> >    mdio:
> >      $ref: /schemas/net/mdio.yaml#
> >      unevaluatedProperties: false
> > +    properties:
> > +      mdio-parent-bus:
> > +        $ref: /schemas/types.yaml#/definitions/phandle
> > +        description:
> > +          Phandle pointing to the MDIO bus controller connected to the
> > +          secondary MDIO interface. This property should be used when
> > +          the internal MDIO bus is accessed via a secondary MDIO
> > +          interface rather than the primary management interface.
> > +
> >      patternProperties:
> >        "^ethernet-phy@[0-9a-f]$":
> >          type: object
> > -- 
> > 2.39.5
> > 
> 
> I'm not saying whether this is good or bad, I'm just worried about
> mixing quantities having different measurement units into the same
> address space.
> 
> Just like in the case of an mdio-mux, there is no address space isolation
> between the parent bus and the child bus. AKA you can't have this,
> because there would be clashes:
> 
> 	host_bus: mdio@abcd {
> 		ethernet-phy@2 {
> 			reg = <2>;
> 		};
> 	};
> 
> 	child_bus: mdio@efgh {
> 		mdio-parent-bus = <&host_bus>;
> 
> 		ethernet-phy@2 {
> 			reg = <2>;
> 		};
> 	};
> 
> But there is a big difference. With an mdio-mux, you could statically
> detect address space clashes by inspecting the PHY addresses on the 2
> buses. But with the lan937x child MDIO bus, in this design, you can't,
> because the "reg" values don't represent MDIO addresses, but switch port
> numbers (this is kind of important, but I don't see it mentioned in the
> dt-binding).

In current state, the driver still require properly configured addresses
in the devicetree. So, it will be visible in the DT.

> These are translated by lan937x_create_phy_addr_map() using
> the CASCADE_ID/VPHY_ADD pin strapping information read over SPI.
> I.e. with the same device tree, you may or may not have address space
> clashes depending on pin strapping. No way to tell.

The PHY address to port mapping in the driver is needed to make the
internal switch interrupt controller assign interrupts to proper PHYs.

It would be possible to assign interrupts per devicetree, but the driver
was previously implemented to not need it, so i decided to follow this
design pattern.

The driver can be extended to validate DT addresses, but I was not sure
that my current decisions are the way to go.

> Have you considered putting the switch's internal PHYs directly under
> the host MDIO bus node, with their 'real' MDIO bus computed statically
> by the DT writer based on the pin straps? Yes, I'm aware that this means
> different pin straps mean different device trees.

Yes, i tried this. In this case, the host MDIO registration procedure
will fail to find the PHYs, because they are not accessible before
switch driver initialization. I had in mind some different variants to
handle it, like:
- use compatible property in the PHY nodes in the host MDIO node.
- trigger MDIO re-scan from the switch
- mimic the MDIO mux. 

The last variant seems to be more or less better fit for this use case.

> Under certain circumstances I could understand this dt-binding design
> with an mdio-parent-bus, like for example if the MDIO addresses at which
> the internal PHYs respond would be configurable over SPI, from the switch
> registers. But I'm not led to believe that here, this is the case.

ack.

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

Re: [PATCH net-next v2 2/5] dt-bindings: net: dsa: ksz: add mdio-parent-bus property for internal MDIO

[Andrew Lunn]

> > I'm not saying whether this is good or bad, I'm just worried about
> > mixing quantities having different measurement units into the same
> > address space.
> > 
> > Just like in the case of an mdio-mux, there is no address space isolation
> > between the parent bus and the child bus. AKA you can't have this,
> > because there would be clashes:
> > 
> > 	host_bus: mdio@abcd {
> > 		ethernet-phy@2 {
> > 			reg = <2>;
> > 		};
> > 	};
> > 
> > 	child_bus: mdio@efgh {
> > 		mdio-parent-bus = <&host_bus>;
> > 
> > 		ethernet-phy@2 {
> > 			reg = <2>;
> > 		};
> > 	};
> > 
> > But there is a big difference. With an mdio-mux, you could statically
> > detect address space clashes by inspecting the PHY addresses on the 2
> > buses. But with the lan937x child MDIO bus, in this design, you can't,
> > because the "reg" values don't represent MDIO addresses, but switch port
> > numbers (this is kind of important, but I don't see it mentioned in the
> > dt-binding).
> 
> In current state, the driver still require properly configured addresses
> in the devicetree. So, it will be visible in the DT.

This is not what i was expecting, especially from mv88e6xxx
perspective. The older generation of devices had the PHYs available on
the 'host bus', as well as the 'child bus', using a 1:1 address
mapping. You could in theory even skip the 'child bus' and list the
PHYs on the 'host bus' and phy-handle would make it work. However i
see from a later comment that does not work here, you need some
configuration done over SPI, which mv88e6xx does not need. 

> 
> > These are translated by lan937x_create_phy_addr_map() using
> > the CASCADE_ID/VPHY_ADD pin strapping information read over SPI.
> > I.e. with the same device tree, you may or may not have address space
> > clashes depending on pin strapping. No way to tell.
> 
> The PHY address to port mapping in the driver is needed to make the
> internal switch interrupt controller assign interrupts to proper PHYs.

You are talking about:

			ds->user_mii_bus->irq[phy] = irq;

in ksz_irq_phy_setup.

I naively expect 'phy' to be the 'reg' value in DT, and the 'dev'
value which passed to mdiobus_read_nested(bus, dev, reg) ?

	Andrew

Re: [PATCH net-next v2 2/5] dt-bindings: net: dsa: ksz: add mdio-parent-bus property for internal MDIO

[Oleksij Rempel]

On Tue, Oct 29, 2024 at 09:35:48PM +0100, Andrew Lunn wrote:
> > > I'm not saying whether this is good or bad, I'm just worried about
> > > mixing quantities having different measurement units into the same
> > > address space.
> > > 
> > > Just like in the case of an mdio-mux, there is no address space isolation
> > > between the parent bus and the child bus. AKA you can't have this,
> > > because there would be clashes:
> > > 
> > > 	host_bus: mdio@abcd {
> > > 		ethernet-phy@2 {
> > > 			reg = <2>;
> > > 		};
> > > 	};
> > > 
> > > 	child_bus: mdio@efgh {
> > > 		mdio-parent-bus = <&host_bus>;
> > > 
> > > 		ethernet-phy@2 {
> > > 			reg = <2>;
> > > 		};
> > > 	};
> > > 
> > > But there is a big difference. With an mdio-mux, you could statically
> > > detect address space clashes by inspecting the PHY addresses on the 2
> > > buses. But with the lan937x child MDIO bus, in this design, you can't,
> > > because the "reg" values don't represent MDIO addresses, but switch port
> > > numbers (this is kind of important, but I don't see it mentioned in the
> > > dt-binding).
> > 
> > In current state, the driver still require properly configured addresses
> > in the devicetree. So, it will be visible in the DT.
> 
> This is not what i was expecting, especially from mv88e6xxx
> perspective. The older generation of devices had the PHYs available on
> the 'host bus', as well as the 'child bus', using a 1:1 address
> mapping. You could in theory even skip the 'child bus' and list the
> PHYs on the 'host bus' and phy-handle would make it work. However i
> see from a later comment that does not work here, you need some
> configuration done over SPI, which mv88e6xx does not need. 
> 
> > 
> > > These are translated by lan937x_create_phy_addr_map() using
> > > the CASCADE_ID/VPHY_ADD pin strapping information read over SPI.
> > > I.e. with the same device tree, you may or may not have address space
> > > clashes depending on pin strapping. No way to tell.
> > 
> > The PHY address to port mapping in the driver is needed to make the
> > internal switch interrupt controller assign interrupts to proper PHYs.
> 
> You are talking about:
> 
> 			ds->user_mii_bus->irq[phy] = irq;
> 
> in ksz_irq_phy_setup.
> 
> I naively expect 'phy' to be the 'reg' value in DT, and the 'dev'
> value which passed to mdiobus_read_nested(bus, dev, reg) ?

Yes, this is correct. This can be implemented purely by parsing the
devicetree. Based on previous experience, I expected you to suggest me
to implement the validation so i jumped directly to a part of this step.

Should I implement it based on the devicetree information and validate
based on HW strapping?

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

Re: [PATCH net-next v2 2/5] dt-bindings: net: dsa: ksz: add mdio-parent-bus property for internal MDIO

[Andrew Lunn]

> Yes, this is correct. This can be implemented purely by parsing the
> devicetree. Based on previous experience, I expected you to suggest me
> to implement the validation so i jumped directly to a part of this step.
> 
> Should I implement it based on the devicetree information and validate
> based on HW strapping?

I assume you need to list the PHYs in DT because there is not a 1:1
mapping of port number to MDIO address? If there is a 1:1 mapping,
port 1 has a PHY at MDIO address 1, the DSA core will connect the PHYs
for you, there is no need to list them in DT.

But if strapping can put them anywhere on the bus, this is not true,
and then you need the phy-handle.

I would then suggest DT described the hardware, the PHYs are listed on
the correct MDIO address, and you validate the hardware matches DT
just as a sanity check.

	Andrew

[PATCH net-next v2 3/5] net: dsa: microchip: Refactor MDIO handling for side MDIO access

[Oleksij Rempel]

Add support for accessing PHYs via a side MDIO interface in LAN937x
switches. The existing code already supports accessing PHYs via main
management interfaces, which can be SPI, I2C, or MDIO, depending on the
chip variant. This patch enables using a side MDIO bus, where SPI is
used for the main switch configuration and MDIO for managing the
integrated PHYs. On LAN937x, this is optional, allowing them to operate
in both configurations: SPI only, or SPI + MDIO. Typically, the SPI
interface is used for switch configuration, while MDIO handles PHY
management.

Additionally, update interrupt controller code to support non-linear
port to PHY address mapping, enabling correct interrupt handling for
configurations where PHY addresses do not directly correspond to port
indexes. This change ensures that the interrupt mechanism properly
aligns with the new, flexible PHY address mappings introduced by side
MDIO support.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
changes v2:
- fail on phy_side_mdio_supported
- add of_node_put(parent_bus_node)
- add comments
---
 drivers/net/dsa/microchip/ksz_common.c | 175 +++++++++++++++++++++++--
 drivers/net/dsa/microchip/ksz_common.h |  59 +++++++++
 2 files changed, 224 insertions(+), 10 deletions(-)

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index 5290f5ad98f39..89134e7fde93b 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -2238,16 +2238,100 @@ static int ksz_sw_mdio_write(struct mii_bus *bus, int addr, int regnum,
 	return dev->dev_ops->w_phy(dev, addr, regnum, val);
 }
 
+/**
+ * ksz_parent_mdio_read - Read data from a PHY register on the parent MDIO bus.
+ * @bus: MDIO bus structure.
+ * @addr: PHY address on the parent MDIO bus.
+ * @regnum: Register number to read.
+ *
+ * This function provides a direct read operation on the parent MDIO bus for
+ * accessing PHY registers. By bypassing SPI or I2C, it uses the parent MDIO bus
+ * to retrieve data from the PHY registers at the specified address and register
+ * number.
+ *
+ * Return: Value of the PHY register, or a negative error code on failure.
+ */
+static int ksz_parent_mdio_read(struct mii_bus *bus, int addr, int regnum)
+{
+	struct ksz_device *dev = bus->priv;
+
+	return mdiobus_read_nested(dev->parent_mdio_bus, addr, regnum);
+}
+
+/**
+ * ksz_parent_mdio_write - Write data to a PHY register on the parent MDIO bus.
+ * @bus: MDIO bus structure.
+ * @addr: PHY address on the parent MDIO bus.
+ * @regnum: Register number to write to.
+ * @val: Value to write to the PHY register.
+ *
+ * This function provides a direct write operation on the parent MDIO bus for
+ * accessing PHY registers. Bypassing SPI or I2C, it uses the parent MDIO bus
+ * to modify the PHY register values at the specified address.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
+static int ksz_parent_mdio_write(struct mii_bus *bus, int addr, int regnum,
+				 u16 val)
+{
+	struct ksz_device *dev = bus->priv;
+
+	return mdiobus_write_nested(dev->parent_mdio_bus, addr, regnum, val);
+}
+
+/**
+ * ksz_phy_addr_to_port - Map a PHY address to the corresponding switch port.
+ * @dev: Pointer to device structure.
+ * @addr: PHY address to map to a port.
+ *
+ * This function finds the corresponding switch port for a given PHY address by
+ * iterating over all user ports on the device. It checks if a port's PHY
+ * address in `phy_addr_map` matches the specified address and if the port
+ * contains an internal PHY. If a match is found, the index of the port is
+ * returned.
+ *
+ * Return: Port index on success, or -EINVAL if no matching port is found.
+ */
+static int ksz_phy_addr_to_port(struct ksz_device *dev, int addr)
+{
+	struct dsa_switch *ds = dev->ds;
+	struct dsa_port *dp;
+
+	dsa_switch_for_each_user_port(dp, ds) {
+		if (dev->info->internal_phy[dp->index] &&
+		    dev->phy_addr_map[dp->index] == addr)
+			return dp->index;
+	}
+
+	return -EINVAL;
+}
+
+/**
+ * ksz_irq_phy_setup - Configure IRQs for PHYs in the KSZ device.
+ * @dev: Pointer to the KSZ device structure.
+ *
+ * Sets up IRQs for each active PHY connected to the KSZ switch by mapping the
+ * appropriate IRQs for each PHY and assigning them to the `user_mii_bus` in
+ * the DSA switch structure. Each IRQ is mapped based on the port's IRQ domain.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
 static int ksz_irq_phy_setup(struct ksz_device *dev)
 {
 	struct dsa_switch *ds = dev->ds;
-	int phy;
+	int phy, port;
 	int irq;
 	int ret;
 
-	for (phy = 0; phy < KSZ_MAX_NUM_PORTS; phy++) {
+	for (phy = 0; phy < PHY_MAX_ADDR; phy++) {
 		if (BIT(phy) & ds->phys_mii_mask) {
-			irq = irq_find_mapping(dev->ports[phy].pirq.domain,
+			port = ksz_phy_addr_to_port(dev, phy);
+			if (port < 0) {
+				ret = port;
+				goto out;
+			}
+
+			irq = irq_find_mapping(dev->ports[port].pirq.domain,
 					       PORT_SRC_PHY_INT);
 			if (irq < 0) {
 				ret = irq;
@@ -2265,40 +2349,109 @@ static int ksz_irq_phy_setup(struct ksz_device *dev)
 	return ret;
 }
 
+/**
+ * ksz_irq_phy_free - Release IRQ mappings for PHYs in the KSZ device.
+ * @dev: Pointer to the KSZ device structure.
+ *
+ * Releases any IRQ mappings previously assigned to active PHYs in the KSZ
+ * switch by disposing of each mapped IRQ in the `user_mii_bus` structure.
+ */
 static void ksz_irq_phy_free(struct ksz_device *dev)
 {
 	struct dsa_switch *ds = dev->ds;
 	int phy;
 
-	for (phy = 0; phy < KSZ_MAX_NUM_PORTS; phy++)
+	for (phy = 0; phy < PHY_MAX_ADDR; phy++)
 		if (BIT(phy) & ds->phys_mii_mask)
 			irq_dispose_mapping(ds->user_mii_bus->irq[phy]);
 }
 
+/**
+ * ksz_mdio_register - Register and configure the MDIO bus for the KSZ device.
+ * @dev: Pointer to the KSZ device structure.
+ *
+ * This function sets up and registers an MDIO bus for the KSZ switch device,
+ * allowing access to its internal PHYs. If the device supports side MDIO,
+ * the function will configure the external MDIO controller specified by the
+ * "mdio-parent-bus" device tree property to directly manage internal PHYs.
+ * Otherwise, SPI or I2C access is set up for PHY access.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
 static int ksz_mdio_register(struct ksz_device *dev)
 {
+	struct device_node *parent_bus_node;
+	struct mii_bus *parent_bus = NULL;
 	struct dsa_switch *ds = dev->ds;
 	struct device_node *mdio_np;
 	struct mii_bus *bus;
-	int ret;
+	struct dsa_port *dp;
+	int ret, i;
 
 	mdio_np = of_get_child_by_name(dev->dev->of_node, "mdio");
 	if (!mdio_np)
 		return 0;
 
+	parent_bus_node = of_parse_phandle(mdio_np, "mdio-parent-bus", 0);
+	if (parent_bus_node && !dev->info->phy_side_mdio_supported) {
+		dev_err(dev->dev, "Side MDIO bus is not supported for this HW, ignoring 'mdio-parent-bus' property.\n");
+		ret = -EINVAL;
+
+		goto put_mdio_node;
+	} else if (parent_bus_node) {
+		parent_bus = of_mdio_find_bus(parent_bus_node);
+		if (!parent_bus) {
+			ret = -EPROBE_DEFER;
+
+			goto put_mdio_node;
+		}
+
+		dev->parent_mdio_bus = parent_bus;
+	}
+
 	bus = devm_mdiobus_alloc(ds->dev);
 	if (!bus) {
 		of_node_put(mdio_np);
 		return -ENOMEM;
 	}
 
+	if (dev->dev_ops->mdio_bus_preinit) {
+		ret = dev->dev_ops->mdio_bus_preinit(dev, !!parent_bus);
+		if (ret)
+			goto put_mdio_node;
+	}
+
+	if (dev->dev_ops->create_phy_addr_map) {
+		ret = dev->dev_ops->create_phy_addr_map(dev, !!parent_bus);
+		if (ret)
+			goto put_mdio_node;
+	} else {
+		for (i = 0; i < dev->info->port_cnt; i++)
+			dev->phy_addr_map[i] = i;
+	}
+
 	bus->priv = dev;
-	bus->read = ksz_sw_mdio_read;
-	bus->write = ksz_sw_mdio_write;
-	bus->name = "ksz user smi";
-	snprintf(bus->id, MII_BUS_ID_SIZE, "SMI-%d", ds->index);
+	if (parent_bus) {
+		bus->read = ksz_parent_mdio_read;
+		bus->write = ksz_parent_mdio_write;
+		bus->name = "KSZ side MDIO";
+		snprintf(bus->id, MII_BUS_ID_SIZE, "ksz-side-mdio-%d",
+			 ds->index);
+	} else {
+		bus->read = ksz_sw_mdio_read;
+		bus->write = ksz_sw_mdio_write;
+		bus->name = "ksz user smi";
+		snprintf(bus->id, MII_BUS_ID_SIZE, "SMI-%d", ds->index);
+	}
+
+	dsa_switch_for_each_user_port(dp, dev->ds) {
+		if (dev->info->internal_phy[dp->index] &&
+		    dev->phy_addr_map[dp->index] < PHY_MAX_ADDR)
+			bus->phy_mask |= BIT(dev->phy_addr_map[dp->index]);
+	}
+
+	ds->phys_mii_mask = bus->phy_mask;
 	bus->parent = ds->dev;
-	bus->phy_mask = ~ds->phys_mii_mask;
 
 	ds->user_mii_bus = bus;
 
@@ -2318,7 +2471,9 @@ static int ksz_mdio_register(struct ksz_device *dev)
 			ksz_irq_phy_free(dev);
 	}
 
+put_mdio_node:
 	of_node_put(mdio_np);
+	of_node_put(parent_bus_node);
 
 	return ret;
 }
diff --git a/drivers/net/dsa/microchip/ksz_common.h b/drivers/net/dsa/microchip/ksz_common.h
index bec846e20682f..bbb548af201ef 100644
--- a/drivers/net/dsa/microchip/ksz_common.h
+++ b/drivers/net/dsa/microchip/ksz_common.h
@@ -65,6 +65,12 @@ struct ksz_chip_data {
 	u8 num_tx_queues;
 	u8 num_ipms; /* number of Internal Priority Maps */
 	bool tc_cbs_supported;
+
+	/**
+	 * @phy_side_mdio_supported: Indicates if the chip supports an additional
+	 * side MDIO channel for accessing integrated PHYs.
+	 */
+	bool phy_side_mdio_supported;
 	const struct ksz_dev_ops *ops;
 	const struct phylink_mac_ops *phylink_mac_ops;
 	bool phy_errata_9477;
@@ -191,6 +197,22 @@ struct ksz_device {
 	struct ksz_switch_macaddr *switch_macaddr;
 	struct net_device *hsr_dev;     /* HSR */
 	u8 hsr_ports;
+
+	/**
+	 * @phy_addr_map: Array mapping switch ports to their corresponding PHY
+	 * addresses.
+	 */
+	u8 phy_addr_map[KSZ_MAX_NUM_PORTS];
+
+	/**
+	 * @parent_mdio_bus: Pointer to the external MDIO bus controller.
+	 *
+	 * This points to an external MDIO bus controller that is used to access
+	 * the  PHYs integrated within the switch. Unlike an integrated MDIO
+	 * bus, this external controller provides a direct path for managing
+	 * the switch’s internal PHYs, bypassing the main SPI interface.
+	 */
+	struct mii_bus *parent_mdio_bus;
 };
 
 /* List of supported models */
@@ -326,6 +348,43 @@ struct ksz_dev_ops {
 	void (*port_cleanup)(struct ksz_device *dev, int port);
 	void (*port_setup)(struct ksz_device *dev, int port, bool cpu_port);
 	int (*set_ageing_time)(struct ksz_device *dev, unsigned int msecs);
+
+	/**
+	 * @mdio_bus_preinit: Function pointer to pre-initialize the MDIO bus
+	 *                    for accessing PHYs.
+	 * @dev: Pointer to device structure.
+	 * @side_mdio: Boolean indicating if the PHYs are accessed over a side
+	 *             MDIO bus.
+	 *
+	 * This function pointer is used to configure the MDIO bus for PHY
+	 * access before initiating regular PHY operations. It enables either
+	 * SPI/I2C or side MDIO access modes by unlocking necessary registers
+	 * and setting up access permissions for the selected mode.
+	 *
+	 * Return:
+	 *  - 0 on success.
+	 *  - Negative error code on failure.
+	 */
+	int (*mdio_bus_preinit)(struct ksz_device *dev, bool side_mdio);
+
+	/**
+	 * @create_phy_addr_map: Function pointer to create a port-to-PHY
+	 *                       address map.
+	 * @dev: Pointer to device structure.
+	 * @side_mdio: Boolean indicating if the PHYs are accessed over a side
+	 *             MDIO bus.
+	 *
+	 * This function pointer is responsible for mapping switch ports to PHY
+	 * addresses according to the configured access mode (SPI or side MDIO)
+	 * and the device’s strap configuration. The mapping setup may vary
+	 * depending on the chip variant and configuration. Ensures the correct
+	 * address mapping for PHY communication.
+	 *
+	 * Return:
+	 *  - 0 on success.
+	 *  - Negative error code on failure (e.g., invalid configuration).
+	 */
+	int (*create_phy_addr_map)(struct ksz_device *dev, bool side_mdio);
 	int (*r_phy)(struct ksz_device *dev, u16 phy, u16 reg, u16 *val);
 	int (*w_phy)(struct ksz_device *dev, u16 phy, u16 reg, u16 val);
 	void (*r_mib_cnt)(struct ksz_device *dev, int port, u16 addr,
-- 
2.39.5

[PATCH net-next v2 4/5] net: dsa: microchip: cleanup error handling in ksz_mdio_register

[Oleksij Rempel]

Replace repeated cleanup code with a single error path using a label.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
 drivers/net/dsa/microchip/ksz_common.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index 89134e7fde93b..f9e45bba2d293 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -2411,8 +2411,8 @@ static int ksz_mdio_register(struct ksz_device *dev)
 
 	bus = devm_mdiobus_alloc(ds->dev);
 	if (!bus) {
-		of_node_put(mdio_np);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto put_mdio_node;
 	}
 
 	if (dev->dev_ops->mdio_bus_preinit) {
@@ -2457,10 +2457,8 @@ static int ksz_mdio_register(struct ksz_device *dev)
 
 	if (dev->irq > 0) {
 		ret = ksz_irq_phy_setup(dev);
-		if (ret) {
-			of_node_put(mdio_np);
-			return ret;
-		}
+		if (ret)
+			goto put_mdio_node;
 	}
 
 	ret = devm_of_mdiobus_register(ds->dev, bus, mdio_np);
-- 
2.39.5

[PATCH net-next v2 5/5] net: dsa: microchip: add support for side MDIO interface in LAN937x

[Oleksij Rempel]

Implement side MDIO channel support for LAN937x switches, providing an
alternative to SPI for PHY management alongside existing SPI-based
switch configuration. This is needed to reduce SPI load, as SPI can be
relatively expensive for small packets compared to MDIO support.

Also, implemented static mappings for PHY addresses for various LAN937x
models to support different internal PHY configurations. Since the PHY
address mappings are not equal to the port indexes, this patch also
provides PHY address calculation based on hardware strapping
configuration.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
changes v2:
- add lan9371_phy_addr map
- add comments
- add define LAN937X_NO_PHY
---
 drivers/net/dsa/microchip/ksz_common.c   |   7 +
 drivers/net/dsa/microchip/lan937x.h      |   2 +
 drivers/net/dsa/microchip/lan937x_main.c | 226 +++++++++++++++++++++--
 drivers/net/dsa/microchip/lan937x_reg.h  |   4 +
 4 files changed, 223 insertions(+), 16 deletions(-)

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index f9e45bba2d293..3909b55857430 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -411,6 +411,8 @@ static const struct ksz_dev_ops lan937x_dev_ops = {
 	.flush_dyn_mac_table = ksz9477_flush_dyn_mac_table,
 	.port_setup = lan937x_port_setup,
 	.set_ageing_time = lan937x_set_ageing_time,
+	.mdio_bus_preinit = lan937x_mdio_bus_preinit,
+	.create_phy_addr_map = lan937x_create_phy_addr_map,
 	.r_phy = lan937x_r_phy,
 	.w_phy = lan937x_w_phy,
 	.r_mib_cnt = ksz9477_r_mib_cnt,
@@ -1762,6 +1764,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,
@@ -1790,6 +1793,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,
@@ -1818,6 +1822,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,
@@ -1850,6 +1855,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,
@@ -1882,6 +1888,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.num_tx_queues = 8,
 		.num_ipms = 8,
 		.tc_cbs_supported = true,
+		.phy_side_mdio_supported = true,
 		.ops = &lan937x_dev_ops,
 		.phylink_mac_ops = &lan937x_phylink_mac_ops,
 		.mib_names = ksz9477_mib_names,
diff --git a/drivers/net/dsa/microchip/lan937x.h b/drivers/net/dsa/microchip/lan937x.h
index 3388d91dbc44e..df13ebbd356f9 100644
--- a/drivers/net/dsa/microchip/lan937x.h
+++ b/drivers/net/dsa/microchip/lan937x.h
@@ -13,6 +13,8 @@ void lan937x_port_setup(struct ksz_device *dev, int port, bool cpu_port);
 void lan937x_config_cpu_port(struct dsa_switch *ds);
 int lan937x_switch_init(struct ksz_device *dev);
 void lan937x_switch_exit(struct ksz_device *dev);
+int lan937x_mdio_bus_preinit(struct ksz_device *dev, bool side_mdio);
+int lan937x_create_phy_addr_map(struct ksz_device *dev, bool side_mdio);
 int lan937x_r_phy(struct ksz_device *dev, u16 addr, u16 reg, u16 *data);
 int lan937x_w_phy(struct ksz_device *dev, u16 addr, u16 reg, u16 val);
 int lan937x_change_mtu(struct ksz_device *dev, int port, int new_mtu);
diff --git a/drivers/net/dsa/microchip/lan937x_main.c b/drivers/net/dsa/microchip/lan937x_main.c
index 824d9309a3d35..b7652efd632ea 100644
--- a/drivers/net/dsa/microchip/lan937x_main.c
+++ b/drivers/net/dsa/microchip/lan937x_main.c
@@ -18,6 +18,87 @@
 #include "ksz9477.h"
 #include "lan937x.h"
 
+/* marker for ports without built-in PHY */
+#define LAN937X_NO_PHY U8_MAX
+
+/*
+ * lan9370_phy_addr - Mapping of LAN9370 switch ports to PHY addresses.
+ *
+ * Each entry corresponds to a specific port on the LAN9370 switch,
+ * where ports 1-4 are connected to integrated 100BASE-T1 PHYs, and
+ * Port 5 is connected to an RGMII interface without a PHY. The values
+ * are based on the documentation (DS00003108E, section 3.3).
+ */
+static const u8 lan9370_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = 6, /* Port 4, T1 AFE4 */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+};
+
+/*
+ * lan9371_phy_addr - Mapping of LAN9371 switch ports to PHY addresses.
+ *
+ * The values are based on the documentation (DS00003109E, section 3.3).
+ */
+static const u8 lan9371_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = 8, /* Port 4, TX PHY */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+	[5] = LAN937X_NO_PHY, /* Port 6, RGMII 1 */
+};
+
+/*
+ * lan9372_phy_addr - Mapping of LAN9372 switch ports to PHY addresses.
+ *
+ * The values are based on the documentation (DS00003110F, section 3.3).
+ */
+static const u8 lan9372_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = 8, /* Port 4, TX PHY */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+	[5] = LAN937X_NO_PHY, /* Port 6, RGMII 1 */
+	[6] = 6, /* Port 7, T1 AFE4 */
+	[7] = 4, /* Port 8, T1 AFE2 */
+};
+
+/*
+ * lan9373_phy_addr - Mapping of LAN9373 switch ports to PHY addresses.
+ *
+ * The values are based on the documentation (DS00003110F, section 3.3).
+ */
+static const u8 lan9373_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = LAN937X_NO_PHY, /* Port 4, SGMII */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+	[5] = LAN937X_NO_PHY, /* Port 6, RGMII 1 */
+	[6] = 6, /* Port 7, T1 AFE4 */
+	[7] = 4, /* Port 8, T1 AFE2 */
+};
+
+/*
+ * lan9374_phy_addr - Mapping of LAN9374 switch ports to PHY addresses.
+ *
+ * The values are based on the documentation (DS00003110F, section 3.3).
+ */
+static const u8 lan9374_phy_addr[] = {
+	[0] = 2, /* Port 1, T1 AFE0 */
+	[1] = 3, /* Port 2, T1 AFE1 */
+	[2] = 5, /* Port 3, T1 AFE3 */
+	[3] = 7, /* Port 4, T1 AFE5 */
+	[4] = LAN937X_NO_PHY, /* Port 5, RGMII 2 */
+	[5] = LAN937X_NO_PHY, /* Port 6, RGMII 1 */
+	[6] = 6, /* Port 7, T1 AFE4 */
+	[7] = 4, /* Port 8, T1 AFE2 */
+};
+
 static int lan937x_cfg(struct ksz_device *dev, u32 addr, u8 bits, bool set)
 {
 	return regmap_update_bits(ksz_regmap_8(dev), addr, bits, set ? bits : 0);
@@ -30,24 +111,144 @@ static int lan937x_port_cfg(struct ksz_device *dev, int port, int offset,
 				  bits, set ? bits : 0);
 }
 
-static int lan937x_enable_spi_indirect_access(struct ksz_device *dev)
+/**
+ * lan937x_create_phy_addr_map - Create port-to-PHY address map for MDIO bus.
+ * @dev: Pointer to device structure.
+ * @side_mdio: Boolean indicating if the PHYs are accessed over a side MDIO bus.
+ *
+ * This function sets up the PHY address mapping for the LAN937x switches,
+ * which support two access modes for internal PHYs:
+ * 1. **SPI Access**: A straightforward one-to-one port-to-PHY address
+ *    mapping is applied.
+ * 2. **MDIO Access**: The PHY address mapping varies based on chip variant
+ *    and strap configuration. An offset is calculated based on strap settings
+ *    to ensure correct PHY addresses are assigned. The offset calculation logic
+ *    is based on Microchip's Article Number 000015828, available at:
+ *    https://microchip.my.site.com/s/article/LAN9374-Virtual-PHY-PHY-Address-Mapping
+ *
+ * The function first checks if side MDIO access is disabled, in which case a
+ * simple direct mapping (port number = PHY address) is applied. If side MDIO
+ * access is enabled, it reads the strap configuration to determine the correct
+ * offset for PHY addresses.
+ *
+ * The appropriate mapping table is selected based on the chip ID, and the
+ * `phy_addr_map` is populated with the correct addresses for each port. Any
+ * port with no PHY is assigned a `LAN937X_NO_PHY` marker.
+ *
+ * Return: 0 on success, error code on failure.
+ */
+int lan937x_create_phy_addr_map(struct ksz_device *dev, bool side_mdio)
+{
+	static const u8 *phy_addr_map;
+	u32 strap_val;
+	u8 offset = 0;
+	size_t size;
+	int ret, i;
+
+	if (!side_mdio) {
+		/* simple direct mapping */
+		for (i = 0; i < dev->info->port_cnt; i++)
+			dev->phy_addr_map[i] = i;
+
+		return 0;
+	}
+
+	ret = ksz_read32(dev, REG_SW_CFG_STRAP_VAL, &strap_val);
+	if (ret < 0)
+		return ret;
+
+	if (!(strap_val & SW_CASCADE_ID_CFG) && !(strap_val & SW_VPHY_ADD_CFG))
+		offset = 0;
+	else if (!(strap_val & SW_CASCADE_ID_CFG) && (strap_val & SW_VPHY_ADD_CFG))
+		offset = 7;
+	else if ((strap_val & SW_CASCADE_ID_CFG) && !(strap_val & SW_VPHY_ADD_CFG))
+		offset = 15;
+	else
+		offset = 22;
+
+	switch (dev->info->chip_id) {
+	case LAN9370_CHIP_ID:
+		phy_addr_map = lan9370_phy_addr;
+		size = ARRAY_SIZE(lan9370_phy_addr);
+		break;
+	case LAN9371_CHIP_ID:
+		phy_addr_map = lan9371_phy_addr;
+		size = ARRAY_SIZE(lan9371_phy_addr);
+		break;
+	case LAN9372_CHIP_ID:
+		phy_addr_map = lan9372_phy_addr;
+		size = ARRAY_SIZE(lan9372_phy_addr);
+		break;
+	case LAN9373_CHIP_ID:
+		phy_addr_map = lan9373_phy_addr;
+		size = ARRAY_SIZE(lan9373_phy_addr);
+		break;
+	case LAN9374_CHIP_ID:
+		phy_addr_map = lan9374_phy_addr;
+		size = ARRAY_SIZE(lan9374_phy_addr);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (size < dev->info->port_cnt)
+		return -EINVAL;
+
+	for (i = 0; i < dev->info->port_cnt; i++) {
+		if (phy_addr_map[i] == LAN937X_NO_PHY)
+			dev->phy_addr_map[i] = phy_addr_map[i];
+		else
+			dev->phy_addr_map[i] = phy_addr_map[i] + offset;
+	}
+
+	return 0;
+}
+
+/**
+ * lan937x_mdio_bus_preinit - Pre-initialize MDIO bus for accessing PHYs.
+ * @dev: Pointer to device structure.
+ * @side_mdio: Boolean indicating if the PHYs are accessed over a side MDIO bus.
+ *
+ * This function configures the LAN937x switch for PHY access either through
+ * SPI or the side MDIO bus, unlocking the necessary registers for each access
+ * mode.
+ *
+ * Operation Modes:
+ * 1. **SPI Access**: Enables SPI indirect access to address clock domain
+ *    crossing issues when SPI is used for PHY access.
+ * 2. **MDIO Access**: Grants access to internal PHYs over the side MDIO bus,
+ *    required when using the MDIO bus for PHY management.
+ *
+ * Return: 0 on success, error code on failure.
+ */
+int lan937x_mdio_bus_preinit(struct ksz_device *dev, bool side_mdio)
 {
 	u16 data16;
 	int ret;
 
-	/* Enable Phy access through SPI */
+	/* Unlock access to the PHYs, needed for SPI and side MDIO access */
 	ret = lan937x_cfg(dev, REG_GLOBAL_CTRL_0, SW_PHY_REG_BLOCK, false);
 	if (ret < 0)
-		return ret;
+		goto print_error;
 
-	ret = ksz_read16(dev, REG_VPHY_SPECIAL_CTRL__2, &data16);
-	if (ret < 0)
-		return ret;
+	if (side_mdio)
+		/* Allow access to internal PHYs over MDIO bus */
+		data16 = VPHY_MDIO_INTERNAL_ENABLE;
+	else
+		/* Enable SPI indirect access to address clock domain crossing
+		 * issue
+		 */
+		data16 = VPHY_SPI_INDIRECT_ENABLE;
 
-	/* Allow SPI access */
-	data16 |= VPHY_SPI_INDIRECT_ENABLE;
+	ret = ksz_rmw16(dev, REG_VPHY_SPECIAL_CTRL__2,
+			VPHY_SPI_INDIRECT_ENABLE | VPHY_MDIO_INTERNAL_ENABLE,
+			data16);
+
+print_error:
+	if (ret < 0)
+		dev_err(dev->dev, "failed to preinit the MDIO bus\n");
 
-	return ksz_write16(dev, REG_VPHY_SPECIAL_CTRL__2, data16);
+	return ret;
 }
 
 static int lan937x_vphy_ind_addr_wr(struct ksz_device *dev, int addr, int reg)
@@ -363,13 +564,6 @@ int lan937x_setup(struct dsa_switch *ds)
 	struct ksz_device *dev = ds->priv;
 	int ret;
 
-	/* enable Indirect Access from SPI to the VPHY registers */
-	ret = lan937x_enable_spi_indirect_access(dev);
-	if (ret < 0) {
-		dev_err(dev->dev, "failed to enable spi indirect access");
-		return ret;
-	}
-
 	/* The VLAN aware is a global setting. Mixed vlan
 	 * filterings are not supported.
 	 */
diff --git a/drivers/net/dsa/microchip/lan937x_reg.h b/drivers/net/dsa/microchip/lan937x_reg.h
index 2f22a9d01de36..4ec93e421da45 100644
--- a/drivers/net/dsa/microchip/lan937x_reg.h
+++ b/drivers/net/dsa/microchip/lan937x_reg.h
@@ -37,6 +37,10 @@
 #define SW_CLK125_ENB			BIT(1)
 #define SW_CLK25_ENB			BIT(0)
 
+#define REG_SW_CFG_STRAP_VAL		0x0200
+#define SW_CASCADE_ID_CFG		BIT(15)
+#define SW_VPHY_ADD_CFG			BIT(0)
+
 /* 2 - PHY Control */
 #define REG_SW_CFG_STRAP_OVR		0x0214
 #define SW_VPHY_DISABLE			BIT(31)
-- 
2.39.5