linux-kernel - Re: [PATCH net-next v3] net: mdio: force deassert MDIO reset signal

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Message-ID: <Y8amwmZLajZfum89@lunn.ch>
Date:   Tue, 17 Jan 2023 14:46:42 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Pierluigi Passaro <pierluigi.p@...iscite.com>
Cc:     hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        eran.m@...iscite.com, nate.d@...iscite.com,
        francesco.f@...iscite.com, pierluigi.passaro@...il.com
Subject: Re: [PATCH net-next v3] net: mdio: force deassert MDIO reset signal

On Mon, Jan 16, 2023 at 05:01:14PM +0100, Pierluigi Passaro wrote:
> When the reset gpio is defined within the node of the device tree
> describing the PHY, the reset is initialized and managed only after
> calling the fwnode_mdiobus_phy_device_register function.
> However, before calling it, the MDIO communication is checked by the
> get_phy_device function.
> When this happens and the reset GPIO was somehow previously set down,
> the get_phy_device function fails, preventing the PHY detection.
> These changes force the deassert of the MDIO reset signal before
> checking the MDIO channel.
> The PHY may require a minimum deassert time before being responsive:
> use a reasonable sleep time after forcing the deassert of the MDIO
> reset signal.
> Once done, free the gpio descriptor to allow managing it later.
> 
> Signed-off-by: Pierluigi Passaro <pierluigi.p@...iscite.com>
> Signed-off-by: FrancescoFerraro <francesco.f@...iscite.com>

FYI: There is still a discussion going on in v1 of this patch. Please
do not merge yet.

   Andrew