linux-kernel - Re: [PATCH net-next v3 02/11] net: phy: introduce phy_has_c45

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Message-ID: <cf999a14e51b7f2001d9830cc5e11016@kernel.org>
Date:   Tue, 01 Aug 2023 16:47:04 +0200
From:   Michael Walle <mwalle@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Marek Behún <kabel@...nel.org>,
        Xu Liang <lxu@...linear.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH net-next v3 02/11] net: phy: introduce
 phy_has_c45_registers()

Hi Andrew,

Am 2023-07-19 09:11, schrieb Michael Walle:
>>> diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
>>> index a64186dc53f8..686a57d56885 100644
>>> --- a/drivers/net/phy/phy-core.c
>>> +++ b/drivers/net/phy/phy-core.c
>>> @@ -556,7 +556,7 @@ int __phy_read_mmd(struct phy_device *phydev, int 
>>> devad, u32 regnum)
>>> 
>>>  	if (phydev->drv && phydev->drv->read_mmd) {
>>>  		val = phydev->drv->read_mmd(phydev, devad, regnum);
>>> -	} else if (phydev->is_c45) {
>>> +	} else if (phy_has_c45_registers(phydev)) {
>> 
>> This i would say should be
>> 
>> phy_has_c45_transfers(phydev). This is about, can we do C45 transfers
>> on the bus, and if not, fall back to C45 over C22.
> 
> Shouldn't this then be a bus property? I.e. 
> mdiobus_has_c45_transfers().
> I've have a similar helper introduced in 9/11:
> 
> static inline bool mdiobus_supports_c45(struct mii_bus *bus)
> {
>     return bus->read_c45 && !bus->prevent_c45_access;
> }
> 
>>>  static int phylink_sfp_connect_phy(void *upstream, struct phy_device 
>>> *phy)
>>> diff --git a/include/linux/phy.h b/include/linux/phy.h
>>> index 11c1e91563d4..fdb3774e99fc 100644
>>> --- a/include/linux/phy.h
>>> +++ b/include/linux/phy.h
>>> @@ -766,6 +766,11 @@ static inline struct phy_device 
>>> *to_phy_device(const struct device *dev)
>>>  	return container_of(to_mdio_device(dev), struct phy_device, mdio);
>>>  }
>>> 
>>> +static inline bool phy_has_c45_registers(struct phy_device *phydev)
>>> +{
>>> +	return phydev->is_c45;
>>> +}
>> 
>> And this is where it gets interesting. I think as a first step, you
>> should implement the four functions:
>> 
>> phy_has_c22_registers()
>> phy_has_c45_registers()
>> phy_has_c22_transfers()
>> phy_has_c45_transfers()
>> 
>> based on this. So there is initially no functional change.
>> 
>> 
>> You can then change the implementation of _transfers() based on what
>> the MDIO bus can do, plus the quirk for if a FUBAR microchip PHY has
>> been found.
> 
> See above. Shouldn't it be mdiobus_...() then?
> 
>> Then change the implementation of _registers() based on the results of
>> probing for the ID registers.
> 
> So this is where I cannot follow. Right now there is
> (1) probing via bus scan
> (2) probing via DT (or maybe also ACPI)
> 
> With (1) you we have scan_c22(), so if successful, 
> phy_has_c22_registers()
> will return true, right? But it's not that clear for
> phy_has_c45_registers(), because sometimes we prevent that scan. So
> the PHY might have c45 but we don't know.
> 
> For (2) we don't even do a c22 scan if we know if its a C45 PHY (or the
> other way around). I'm not sure we can reliably tell (at the end of 
> this
> series) if a phy has c22 register, c45 registers or both.

Any news here?

-michael