linux-kernel - Re: [PATCH v2] net: mdio: force deassert MDIO reset signal

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Message-ID: <AM6PR08MB43764E8EB99B48897327CFCCFFC19@AM6PR08MB4376.eurprd08.prod.outlook.com>
Date:   Mon, 16 Jan 2023 13:13:49 +0000
From:   Pierluigi Passaro <pierluigi.p@...iscite.com>
To:     Simon Horman <simon.horman@...igine.com>
CC:     "andrew@...n.ch" <andrew@...n.ch>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "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>,
        "pierluigi.passaro@...il.com" <pierluigi.passaro@...il.com>
Subject: Re: [PATCH v2] net: mdio: force deassert MDIO reset signal

On Mon, Jan 16, 2023 at 12:10 PM Simon Horman <simon.horman@...igine.com> wrote:
> On Sun, Jan 15, 2023 at 10:37:46PM +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>
> > ---
> >  drivers/net/mdio/fwnode_mdio.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/drivers/net/mdio/fwnode_mdio.c b/drivers/net/mdio/fwnode_mdio.c
> > index b782c35c4ac1..1f4b8c4c1f60 100644
> > --- a/drivers/net/mdio/fwnode_mdio.c
> > +++ b/drivers/net/mdio/fwnode_mdio.c
> > @@ -8,6 +8,8 @@
> >
> >  #include <linux/acpi.h>
> >  #include <linux/fwnode_mdio.h>
> > +#include <linux/gpio/consumer.h>
> > +#include <linux/gpio/driver.h>
> >  #include <linux/of.h>
> >  #include <linux/phy.h>
> >  #include <linux/pse-pd/pse.h>
> > @@ -118,6 +120,8 @@ int fwnode_mdiobus_register_phy(struct mii_bus *bus,
> >       bool is_c45 = false;
> >       u32 phy_id;
> >       int rc;
> > +     int reset_deassert_delay = 0;
>
> nit: it looks like scope of reset_deassert_delay could be reduced
>      to the else clause where it is used.
>
no problem.
>
> > +     struct gpio_desc *reset_gpio;
>
> nit: reverse xmas tree for local variable declarations
>
I'm worried I'm asking something stupid: what do you mean by
"reverse xmas tree" ?> ...
>
> Also, if reposting, the target tree for this should be in the subject.
> Assuming net-next, that would mean "[PATCH net-next v3]"
>
no problem