[PATCH net] net: mdio-mux: fix C45 access returning -EIO after API change

[PATCH net] net: mdio-mux: fix C45 access returning -EIO after API change

[Vladimir Oltean]

The mii_bus API conversion to read_c45() and write_c45() did not cover
the mdio-mux driver before read() and write() were made C22-only.

This broke arch/arm64/boot/dts/freescale/fsl-ls1028a-qds-13bb.dtso.
The -EOPNOTSUPP from mdiobus_c45_read() is transformed by
get_phy_c45_devs_in_pkg() into -EIO, is further propagated to
of_mdiobus_register() and this makes the mdio-mux driver fail to probe
the entire child buses, not just the PHYs that cause access errors.

Fix the regression by introducing special c45 read and write accessors
to mdio-mux which forward the operation to the parent MDIO bus.

Fixes: db1a63aed89c ("net: phy: Remove fallback to old C45 method")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 drivers/net/mdio/mdio-mux.c | 45 +++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/drivers/net/mdio/mdio-mux.c b/drivers/net/mdio/mdio-mux.c
index a881e3523328..7d322c08c1e9 100644
--- a/drivers/net/mdio/mdio-mux.c
+++ b/drivers/net/mdio/mdio-mux.c
@@ -55,6 +55,27 @@ static int mdio_mux_read(struct mii_bus *bus, int phy_id, int regnum)
 	return r;
 }
 
+static int mdio_mux_read_c45(struct mii_bus *bus, int phy_id, int dev_addr,
+			     int regnum)
+{
+	struct mdio_mux_child_bus *cb = bus->priv;
+	struct mdio_mux_parent_bus *pb = cb->parent;
+	int r;
+
+	mutex_lock_nested(&pb->mii_bus->mdio_lock, MDIO_MUTEX_MUX);
+	r = pb->switch_fn(pb->current_child, cb->bus_number, pb->switch_data);
+	if (r)
+		goto out;
+
+	pb->current_child = cb->bus_number;
+
+	r = pb->mii_bus->read_c45(pb->mii_bus, phy_id, dev_addr, regnum);
+out:
+	mutex_unlock(&pb->mii_bus->mdio_lock);
+
+	return r;
+}
+
 /*
  * The parent bus' lock is used to order access to the switch_fn.
  */
@@ -80,6 +101,28 @@ static int mdio_mux_write(struct mii_bus *bus, int phy_id,
 	return r;
 }
 
+static int mdio_mux_write_c45(struct mii_bus *bus, int phy_id, int dev_addr,
+			      int regnum, u16 val)
+{
+	struct mdio_mux_child_bus *cb = bus->priv;
+	struct mdio_mux_parent_bus *pb = cb->parent;
+
+	int r;
+
+	mutex_lock_nested(&pb->mii_bus->mdio_lock, MDIO_MUTEX_MUX);
+	r = pb->switch_fn(pb->current_child, cb->bus_number, pb->switch_data);
+	if (r)
+		goto out;
+
+	pb->current_child = cb->bus_number;
+
+	r = pb->mii_bus->write_c45(pb->mii_bus, phy_id, dev_addr, regnum, val);
+out:
+	mutex_unlock(&pb->mii_bus->mdio_lock);
+
+	return r;
+}
+
 static int parent_count;
 
 static void mdio_mux_uninit_children(struct mdio_mux_parent_bus *pb)
@@ -173,6 +216,8 @@ int mdio_mux_init(struct device *dev,
 		cb->mii_bus->parent = dev;
 		cb->mii_bus->read = mdio_mux_read;
 		cb->mii_bus->write = mdio_mux_write;
+		cb->mii_bus->read_c45 = mdio_mux_read_c45;
+		cb->mii_bus->write_c45 = mdio_mux_write_c45;
 		r = of_mdiobus_register(cb->mii_bus, child_bus_node);
 		if (r) {
 			mdiobus_free(cb->mii_bus);
-- 
2.34.1

Re: [PATCH net] net: mdio-mux: fix C45 access returning -EIO after API change

[Russell King (Oracle)]

On Tue, Oct 17, 2023 at 02:32:22PM +0300, Vladimir Oltean wrote:
> The mii_bus API conversion to read_c45() and write_c45() did not cover
> the mdio-mux driver before read() and write() were made C22-only.
> 
> This broke arch/arm64/boot/dts/freescale/fsl-ls1028a-qds-13bb.dtso.
> The -EOPNOTSUPP from mdiobus_c45_read() is transformed by
> get_phy_c45_devs_in_pkg() into -EIO, is further propagated to
> of_mdiobus_register() and this makes the mdio-mux driver fail to probe
> the entire child buses, not just the PHYs that cause access errors.
> 
> Fix the regression by introducing special c45 read and write accessors
> to mdio-mux which forward the operation to the parent MDIO bus.
> 
> Fixes: db1a63aed89c ("net: phy: Remove fallback to old C45 method")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
>  drivers/net/mdio/mdio-mux.c | 45 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/drivers/net/mdio/mdio-mux.c b/drivers/net/mdio/mdio-mux.c
> index a881e3523328..7d322c08c1e9 100644
> --- a/drivers/net/mdio/mdio-mux.c
> +++ b/drivers/net/mdio/mdio-mux.c
> @@ -55,6 +55,27 @@ static int mdio_mux_read(struct mii_bus *bus, int phy_id, int regnum)
>  	return r;
>  }
>  
> +static int mdio_mux_read_c45(struct mii_bus *bus, int phy_id, int dev_addr,
> +			     int regnum)
> +{
> +	struct mdio_mux_child_bus *cb = bus->priv;
> +	struct mdio_mux_parent_bus *pb = cb->parent;
> +	int r;
> +
> +	mutex_lock_nested(&pb->mii_bus->mdio_lock, MDIO_MUTEX_MUX);
> +	r = pb->switch_fn(pb->current_child, cb->bus_number, pb->switch_data);
> +	if (r)
> +		goto out;
> +
> +	pb->current_child = cb->bus_number;
> +
> +	r = pb->mii_bus->read_c45(pb->mii_bus, phy_id, dev_addr, regnum);

What if the parent bus doesn't have read_c45 or write_c45 ?

> @@ -173,6 +216,8 @@ int mdio_mux_init(struct device *dev,
>  		cb->mii_bus->parent = dev;
>  		cb->mii_bus->read = mdio_mux_read;
>  		cb->mii_bus->write = mdio_mux_write;
> +		cb->mii_bus->read_c45 = mdio_mux_read_c45;
> +		cb->mii_bus->write_c45 = mdio_mux_write_c45;

Maybe make these conditional on the parent bus implementing the c45
read/write ops?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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Re: [PATCH net] net: mdio-mux: fix C45 access returning -EIO after API change

[Andrew Lunn]

> Maybe make these conditional on the parent bus implementing the c45
> read/write ops?

And optionally, for net-next, make the c22 read/write ops conditional
on the parent bus having C22 as well. Its a bit of a corner case, but
there are a couple of MDIO bus masters which are C45 only.

Not having C45 is however very common, so we should make this
conditional as part of the fix.

      Andrew

Re: [PATCH net] net: mdio-mux: fix C45 access returning -EIO after API change

[Vladimir Oltean]

On Tue, Oct 17, 2023 at 02:31:30PM +0100, Russell King (Oracle) wrote:
> What if the parent bus doesn't have read_c45 or write_c45 ?

Good question. Predictably, the kernel crashes.

> Maybe make these conditional on the parent bus implementing the c45
> read/write ops?

I can do that, and send a v2 right away. Thanks for the hint.

Re: [PATCH net] net: mdio-mux: fix C45 access returning -EIO after API change

[Vladimir Oltean]

On Tue, Oct 17, 2023 at 03:44:58PM +0200, Andrew Lunn wrote:
> > Maybe make these conditional on the parent bus implementing the c45
> > read/write ops?
> 
> And optionally, for net-next, make the c22 read/write ops conditional
> on the parent bus having C22 as well. Its a bit of a corner case, but
> there are a couple of MDIO bus masters which are C45 only.
> 
> Not having C45 is however very common, so we should make this
> conditional as part of the fix.
> 
>       Andrew

Ok. I don't know if net-next will remain open after this patch gets
accepted and "net" gets merged back into it, so in order to not
completely forget, I'll add a patch with your suggestion to our
Layerscape SDK and that will serve as a reminder for the next
upstreaming session.

In the meantime, for this patch:

pw-bot: cr