linux-kernel - Re: [PATCH] net: mdio: force deassert MDIO reset signal

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Message-ID: <Y8UlQaymWcYdqKJ/@shell.armlinux.org.uk>
Date:   Mon, 16 Jan 2023 10:21:53 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Pierluigi Passaro <pierluigi.p@...iscite.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Pierluigi Passaro <pierluigi.passaro@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Eran Matityahu <eran.m@...iscite.com>,
        Nate Drude <Nate.D@...iscite.com>,
        Francesco Ferraro <francesco.f@...iscite.com>
Subject: Re: [PATCH] net: mdio: force deassert MDIO reset signal

On Mon, Jan 16, 2023 at 09:44:01AM +0000, Pierluigi Passaro wrote:
> I can't really understand why the MDIO bus must check the PHY presence.
> Other busses try the communication only while probing the slaves,
> never before.

That is not true.

Any bus that relies on hardware identification to bind drivers reads
the identifying information prior to probing. For example, PCI, USB,
AMBA to name a few. AMBA didn't used to have this problem, but does
now - but at least under AMBA there's a bit more standardisation to
what needs to be done. With ethernet PHYs, what's needed is highly
platform specific.

-- 
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