Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Ioana Ciornei <ioana.ciornei@nxp.com>
To:     Andrew Lunn <andrew@lunn.ch>
CC:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-renesas-soc@vger.kernel.org" 
        <linux-renesas-soc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] [RFC] net: phy: Fix reboot crash if CONFIG_IP_PNP is not
 set
Thread-Topic: [PATCH] [RFC] net: phy: Fix reboot crash if CONFIG_IP_PNP is not
 set
Thread-Index: AQHW4pSHwxyh2hM/e0O6/3UMlPC3maoXjZOAgAAE5QCAAB7HAIAABB2AgAAEPYCAABRIgA==
Date:   Mon, 4 Jan 2021 18:43:42 +0000
Message-ID: <20210104184341.szvnl24wnfnxg4k7@skbuf>
References: <20210104122415.1263541-1-geert+renesas@glider.be>
 <20210104145331.tlwjwbzey5i4vgvp@skbuf>
 <CAMuHMdUVsSuAur1wWkjs7FW5N-36XV9iXA6wmvst59eKoUFDHQ@mail.gmail.com>
 <20210104170112.hn6t3kojhifyuaf6@skbuf> <X/NNS3FUeSNxbqwo@lunn.ch>
 <X/NQ2fYdBygm3CYc@lunn.ch>
In-Reply-To: <X/NQ2fYdBygm3CYc@lunn.ch>
Accept-Language: en-US
Content-Language: en-US
Content-Type: text/plain; charset="us-ascii"
Content-ID: <35D2D4A914A4AF4BAE9FA5DA1262AB1C@eurprd04.prod.outlook.com>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: eb924217-bc28-4f29-4830-08d8b0e0a92f
X-MS-Exchange-CrossTenant-originalarrivaltime: 04 Jan 2021 18:43:42.9436
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: 66BSPE4PdIMSUZSuYJ7uH+mdZ3crZd1gxIojkWVfiRwd6mAG/OTmYLHYqBVS7mWX2Ej+Ac1ne/M0dNXIjdyB4g==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR0402MB3469
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, Jan 04, 2021 at 06:31:05PM +0100, Andrew Lunn wrote:
> > The basic rules here should be, if the MDIO bus is registered, it is
> > usable. There are things like PHY statistics, HWMON temperature
> > sensors, etc, DSA switches, all which have a life cycle separate to
> > the interface being up.
>=20
> [Goes and looks at the code]
>=20
> Yes, this is runtime PM which is broken.
>=20
> sh_mdio_init() needs to wrap the mdp->mii_bus->read and
> mdp->mii_bus->write calls with calls to
>=20
> pm_runtime_get_sync(&mdp->pdev->dev);
>=20
> and
>=20
> pm_runtime_put_sync(&mdp->pdev->dev);
>=20

Agree. Thanks for actually looking into it.. I'm not really well versed
in runtime PM.

> The KSZ8041RNLI supports statistics, which ethtool --phy-stats can
> read, and these will also going to cause problems.
>=20

Not really, this driver connects to the PHY on .ndo_open(), thus any
try to actually dump the PHY statistics before an ifconfig up would get
an -EOPNOTSUPP since the dev->phydev is not yet populated.

This is exactly why I do not understand why some drivers insist on
calling of_phy_connect() and its variants on .ndo_open() and not while
probing the device - you can access the debug stats only if the
interface was started.=