linux-kernel - Re: [PATCH net-next v3 03/11] net: phy: replace is_c45 with phy_accces

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Date:   Tue, 18 Jul 2023 21:53:25 +0200
From:   Michael Walle <mwalle@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     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 03/11] net: phy: replace is_c45 with
 phy_accces_mode

Am 2023-07-18 19:40, schrieb Andrew Lunn:
>>  static inline bool phy_has_c45_registers(struct phy_device *phydev)
>>  {
>> -	return phydev->is_c45;
>> +	return phydev->access_mode != PHY_ACCESS_C22;
>>  }
> 
> So this is making me wounder if we have a clean separation between
> register spaces and access methods.

The idea is to at least have it behind a helper which can be changed
if we get that information from somewhere else.

But right now, a PHY is considered to have c45 registers if it is
probed via c45 (accesses).

Instead of checking the access mode, I could also introduce a
bitmask(?)/flags has_c22/has_c45_registers. But how would you tell
if a PHY as c22 registers? Probe both c22 and c45? What if the bus
can't do c45?

> Should there be a phy_has_c22_registers() ?
> 
> A PHY can have both C22 registers and C45 registers. It is up to the
> driver to decide which it wants to access when.

But isn't it also the driver which has the ultimate information whether
a PHY has c22 register space and/or c45 one?

Maybe we need to clarify what "has c22/c45 registers space" actually
means. Responds to MII c22/c45 access?

-michael

> Should phydev->access_mode really be phydev->access_mode_c45_registers
> to indicate how to access the C45 registers if phy_has_c45_registers()
> is true?
> 
> Has there been a review of all uses of phydev->is_c45 to determine if
> the user wants to know if C45 registers exist,
> a.k.a. phy_has_c45_registers(), or if C45 bus transactions can be
> performed, and then later in this series, additionally if C45 over C22
> can be performed. These are different things.
> 
> I need to keep reading the patches...
> 
>   Andrew