linux-kernel - RE: [PATCH 1/2] net: mdio: add reset deassertion for Aspeed MDIO

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Date:   Mon, 21 Mar 2022 08:20:01 +0000
From:   Dylan Hung <dylan_hung@...eedtech.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "joel@....id.au" <joel@....id.au>,
        "andrew@...id.au" <andrew@...id.au>,
        "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>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     BMC-SW <BMC-SW@...eedtech.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH 1/2] net: mdio: add reset deassertion for Aspeed MDIO

> -----Original Message-----
> From: Philipp Zabel [mailto:p.zabel@...gutronix.de]
> Sent: 2022年3月21日 4:15 PM
> To: Dylan Hung <dylan_hung@...eedtech.com>; robh+dt@...nel.org;
> joel@....id.au; andrew@...id.au; andrew@...n.ch; hkallweit1@...il.com;
> linux@...linux.org.uk; davem@...emloft.net; kuba@...nel.org;
> pabeni@...hat.com; devicetree@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org; linux-aspeed@...ts.ozlabs.org;
> linux-kernel@...r.kernel.org; netdev@...r.kernel.org
> Cc: BMC-SW <BMC-SW@...eedtech.com>; stable@...r.kernel.org
> Subject: Re: [PATCH 1/2] net: mdio: add reset deassertion for Aspeed MDIO
> 
> Hi Dylan,
> 
> On Mo, 2022-03-21 at 15:01 +0800, Dylan Hung wrote:
> > Add reset deassertion for Aspeed MDIO.  There are 4 MDIO controllers
> > embedded in Aspeed AST2600 SOC and share one reset control register
> > SCU50[3]. So devm_reset_control_get_shared is used in this change.
> >
> > Signed-off-by: Dylan Hung <dylan_hung@...eedtech.com>
> > Cc: stable@...r.kernel.org
> > ---
> >  drivers/net/mdio/mdio-aspeed.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/net/mdio/mdio-aspeed.c b/drivers/net/mdio/mdio-
> > aspeed.c index e2273588c75b..8ac262a12d13 100644
> > --- a/drivers/net/mdio/mdio-aspeed.c
> > +++ b/drivers/net/mdio/mdio-aspeed.c
> > @@ -3,6 +3,7 @@
> >
> >  #include <linux/bitfield.h>
> >  #include <linux/delay.h>
> > +#include <linux/reset.h>
> >  #include <linux/iopoll.h>
> >  #include <linux/mdio.h>
> >  #include <linux/module.h>
> > @@ -37,6 +38,7 @@
> >
> >  struct aspeed_mdio {
> >         void __iomem *base;
> > +       struct reset_control *reset;
> >  };
> >
> >  static int aspeed_mdio_read(struct mii_bus *bus, int addr, int
> > regnum)
> > @@ -120,6 +122,12 @@ static int aspeed_mdio_probe(struct
> > platform_device *pdev)
> >         if (IS_ERR(ctx->base))
> >                 return PTR_ERR(ctx->base);
> >
> > +       ctx->reset = devm_reset_control_get_shared(&pdev->dev, NULL);
> 
> The device tree bindings should have a required reset control property
> documented before this is added.
> 

OK, I will add a commit for the document in V2.

> > +       if (IS_ERR(ctx->reset))
> > +               return PTR_ERR(ctx->reset);
> > +
> > +       reset_control_deassert(ctx->reset);
> > +
> 
> This is missing a corresponding reset_control_assert() in
> aspeed_mdio_remove() and in the error path of of_mdiobus_register().
> That would allow to assert the reset line again after all MDIO controllers are
> unbound.

Thank you for your comment. I will fix it in V2.

> 
> regards
> Philipp

--
Dylan