netdev - RE: [net-next PATCH v2 1/3] net: phy: Allow mdio buses to auto-probe c45 devices

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Date:   Mon, 22 Jun 2020 09:29:17 +0000
From:   "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>
To:     "Calvin Johnson (OSS)" <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>,
        Florian Fainelli <f.fainelli@...il.com>,
        "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>
CC:     "linux.cj@...il.com" <linux.cj@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [net-next PATCH v2 1/3] net: phy: Allow mdio buses to auto-probe
 c45 devices

> -----Original Message-----
> From: Calvin Johnson (OSS) <calvin.johnson@....nxp.com>
> Sent: Monday, June 22, 2020 11:19 AM
> To: 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>;
> Florian Fainelli <f.fainelli@...il.com>; Madalin Bucur (OSS)
> <madalin.bucur@....nxp.com>
> Cc: linux.cj@...il.com; netdev@...r.kernel.org; Calvin Johnson (OSS)
> <calvin.johnson@....nxp.com>
> Subject: [net-next PATCH v2 1/3] net: phy: Allow mdio buses to auto-probe
> c45 devices
> 
> From: Jeremy Linton <jeremy.linton@....com>
> 
> The mdiobus_scan logic is currently hardcoded to only
> work with c22 devices. This works fairly well in most
> cases, but its possible that a c45 device doesn't respond
> despite being a standard phy. If the parent hardware
> is capable, it makes sense to scan for c22 devices before
> falling back to c45.
> 
> As we want this to reflect the capabilities of the STA,
> lets add a field to the mii_bus structure to represent
> the capability. That way devices can opt into the extended
> scanning. Existing users should continue to default to c22
> only scanning as long as they are zero'ing the structure
> before use.

How is this default working for existing users, the code below does not seem
to do anything for a zeroed struct, as there is no default in the switch?

> 
> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
> Signed-off-by: Calvin Johnson <calvin.johnson@....nxp.com>
> 
> ---
> 
> Changes in v2:
> - Reserve "0" to mean that no mdiobus capabilities have been declared.
> 
>  drivers/net/phy/mdio_bus.c | 17 +++++++++++++++--
>  include/linux/phy.h        |  8 ++++++++
>  2 files changed, 23 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
> index 6ceee82b2839..e6c179b89907 100644
> --- a/drivers/net/phy/mdio_bus.c
> +++ b/drivers/net/phy/mdio_bus.c
> @@ -739,10 +739,23 @@ EXPORT_SYMBOL(mdiobus_free);
>   */
>  struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr)
>  {
> -	struct phy_device *phydev;
> +	struct phy_device *phydev = ERR_PTR(-ENODEV);
>  	int err;
> 
> -	phydev = get_phy_device(bus, addr, false);
> +	switch (bus->probe_capabilities) {
> +	case MDIOBUS_C22:
> +		phydev = get_phy_device(bus, addr, false);
> +		break;
> +	case MDIOBUS_C45:
> +		phydev = get_phy_device(bus, addr, true);
> +		break;
> +	case MDIOBUS_C22_C45:
> +		phydev = get_phy_device(bus, addr, false);
> +		if (IS_ERR(phydev))
> +			phydev = get_phy_device(bus, addr, true);
> +		break;
> +	}
> +
>  	if (IS_ERR(phydev))
>  		return phydev;
> 
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index 9248dd2ce4ca..7860d56c6bf5 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -298,6 +298,14 @@ struct mii_bus {
>  	/* RESET GPIO descriptor pointer */
>  	struct gpio_desc *reset_gpiod;
> 
> +	/* bus capabilities, used for probing */
> +	enum {
> +		MDIOBUS_NO_CAP = 0,
> +		MDIOBUS_C22,
> +		MDIOBUS_C45,
> +		MDIOBUS_C22_C45,
> +	} probe_capabilities;
> +
>  	/* protect access to the shared element */
>  	struct mutex shared_lock;
> 
> --
> 2.17.1