netdev - Re: [net-next PATCH v6 4/6] net: phy: introduce phy_find_by_mdio

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Date:   Sat, 11 Jul 2020 14:41:12 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Calvin Johnson <calvin.johnson@....nxp.com>,
        Jeremy Linton <jeremy.linton@....com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Jon <jon@...id-run.com>,
        Cristi Sovaiala <cristian.sovaiala@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Madalin Bucur <madalin.bucur@....nxp.com>
Cc:     netdev@...r.kernel.org, linux.cj@...il.com,
        linux-acpi@...r.kernel.org
Subject: Re: [net-next PATCH v6 4/6] net: phy: introduce
 phy_find_by_mdio_handle()



On 7/10/2020 11:55 PM, Calvin Johnson wrote:
> The PHYs on an mdiobus are probed and registered using mdiobus_register().
> Later, for connecting these PHYs to MAC, the PHYs registered on the
> mdiobus have to be referenced.
> 
> For each MAC node, a property "mdio-handle" is used to reference the
> MDIO bus on which the PHYs are registered. On getting hold of the MDIO
> bus, use phy_find_by_fwnode() to get the PHY connected to the MAC.
> 
> Introduce fwnode_mdio_find_bus() to find the mii_bus that corresponds
> to given mii_bus fwnode.
> 
> Signed-off-by: Calvin Johnson <calvin.johnson@....nxp.com>
> 
> ---
> 
> Changes in v6: None
> Changes in v5:
> - rename phy_find_by_fwnode() to phy_find_by_mdio_handle()
> - add docment for phy_find_by_mdio_handle()
> - error out DT in phy_find_by_mdio_handle()
> - clean up err return
> 
> Changes in v4:
> - release fwnode_mdio after use
> - return ERR_PTR instead of NULL
> 
> Changes in v3:
> - introduce fwnode_mdio_find_bus()
> - renamed and improved phy_find_by_fwnode()
> 
> Changes in v2: None
> 
>  drivers/net/phy/mdio_bus.c   | 25 ++++++++++++++++++++++
>  drivers/net/phy/phy_device.c | 40 ++++++++++++++++++++++++++++++++++++
>  include/linux/phy.h          |  2 ++
>  3 files changed, 67 insertions(+)
> 
> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
> index 8610f938f81f..d9597c5b55ae 100644
> --- a/drivers/net/phy/mdio_bus.c
> +++ b/drivers/net/phy/mdio_bus.c
> @@ -435,6 +435,31 @@ struct mii_bus *of_mdio_find_bus(struct device_node *mdio_bus_np)
>  }
>  EXPORT_SYMBOL(of_mdio_find_bus);
>  
> +/**
> + * fwnode_mdio_find_bus - Given an mii_bus fwnode, find the mii_bus.
> + * @mdio_bus_fwnode: fwnode of the mii_bus.
> + *
> + * Returns a reference to the mii_bus, or NULL if none found.  The
> + * embedded struct device will have its reference count incremented,
> + * and this must be put once the bus is finished with.
> + *
> + * Because the association of a fwnode and mii_bus is made via
> + * mdiobus_register(), the mii_bus cannot be found before it is
> + * registered with mdiobus_register().
> + *
> + */
> +struct mii_bus *fwnode_mdio_find_bus(struct fwnode_handle *mdio_bus_fwnode)
> +{
> +	struct device *d;
> +
> +	if (!mdio_bus_fwnode)
> +		return NULL;
> +
> +	d = class_find_device_by_fwnode(&mdio_bus_class, mdio_bus_fwnode);
> +	return d ? to_mii_bus(d) : NULL;
> +}
> +EXPORT_SYMBOL(fwnode_mdio_find_bus);
> +
>  /* Walk the list of subnodes of a mdio bus and look for a node that
>   * matches the mdio device's address with its 'reg' property. If
>   * found, set the of_node pointer for the mdio device. This allows
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 7cda95330aea..00b2ade9714f 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -23,8 +23,10 @@
>  #include <linux/mm.h>
>  #include <linux/module.h>
>  #include <linux/netdevice.h>
> +#include <linux/of.h>
>  #include <linux/phy.h>
>  #include <linux/phy_led_triggers.h>
> +#include <linux/platform_device.h>
>  #include <linux/property.h>
>  #include <linux/sfp.h>
>  #include <linux/skbuff.h>
> @@ -964,6 +966,44 @@ struct phy_device *phy_find_first(struct mii_bus *bus)
>  }
>  EXPORT_SYMBOL(phy_find_first);
>  
> +/**
> + * phy_find_by_mdio_handle - get phy device from mdio-handle and phy-channel
> + * @fwnode: a pointer to a &struct fwnode_handle  to get mdio-handle and
> + * phy-channel
> + *
> + * Find fwnode_mdio using mdio-handle reference. Using fwnode_mdio get the
> + * mdio bus. Property phy-channel provides the phy address on the mdio bus.
> + * Pass mdio bus and phy address to mdiobus_get_phy() and get corresponding
> + * phy_device. This method is used for ACPI and not for DT.
> + *
> + * Returns pointer to the phy device on success, else ERR_PTR.
> + */
> +struct phy_device *phy_find_by_mdio_handle(struct fwnode_handle *fwnode)
> +{
> +	struct fwnode_handle *fwnode_mdio;
> +	struct mii_bus *mdio;
> +	int addr;
> +	int err;
> +
> +	if (is_of_node(fwnode))
> +		return ERR_PTR(-EINVAL);
> +
> +	fwnode_mdio = fwnode_find_reference(fwnode, "mdio-handle", 0);

I would export the positional argument here to phy_find_by_mdio_handle()
but have no strong opinion if this is not done right now and punted to
when another users comes in.

> +	mdio = fwnode_mdio_find_bus(fwnode_mdio);
> +	fwnode_handle_put(fwnode_mdio);
> +	if (!mdio)
> +		return ERR_PTR(-ENODEV);
> +
> +	err = fwnode_property_read_u32(fwnode, "phy-channel", &addr);
> +	if (err)
> +		return ERR_PTR(err);
> +	if (addr < 0 || addr >= PHY_MAX_ADDR)

Can an u32 ever be < 0?
-- 
Florian