From: "Voon, Weifeng" <weifeng.voon@intel.com>
To: Andrew Lunn <andrew@lunn.ch>, Florian Fainelli <f.fainelli@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Maxime Coquelin <mcoquelin.stm32@gmail.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Jose Abreu <joabreu@synopsys.com>,
"Heiner Kallweit" <hkallweit1@gmail.com>,
"Ong, Boon Leong" <boon.leong.ong@intel.com>
Subject: RE: [PATCH v1 net-next] net: phy: mdio_bus: make mdiobus_scan also cover PHY that only talks C45
Date: Tue, 27 Aug 2019 15:23:34 +0000 [thread overview]
Message-ID: <D6759987A7968C4889FDA6FA91D5CBC814758ED8@PGSMSX103.gar.corp.intel.com> (raw)
In-Reply-To: <20190826185418.GG2168@lunn.ch>
> > > Make mdiobus_scan() to try harder to look for any PHY that only
> talks C45.
> > If you are not using Device Tree or ACPI, and you are letting the MDIO
> > bus be scanned, it sounds like there should be a way for you to
> > provide a hint as to which addresses should be scanned (that's
> > mii_bus::phy_mask) and possibly enhance that with a mask of possible
> > C45 devices?
>
> Yes, i don't like this unconditional c45 scanning. A lot of MDIO bus
> drivers don't look for the MII_ADDR_C45. They are going to do a C22
> transfer, and maybe not mask out the MII_ADDR_C45 from reg, causing an
> invalid register write. Bad things can then happen.
>
> With DT and ACPI, we have an explicit indication that C45 should be used,
> so we know on this platform C45 is safe to use. We need something
> similar when not using DT or ACPI.
>
> Andrew
Florian and Andrew,
The mdio c22 is using the start-of-frame ST=01 while mdio c45 is using ST=00
as identifier. So mdio c22 device will not response to mdio c45 protocol.
As in IEEE 802.1ae-2002 Annex 45A.3 mention that:
" Even though the Clause 45 MDIO frames using the ST=00 frame code
will also be driven on to the Clause 22 MII Management interface,
the Clause 22 PHYs will ignore the frames. "
Hence, I am not seeing any concern that the c45 scanning will mess up with
c22 devices.
Weifeng
next prev parent reply other threads:[~2019-08-27 15:23 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 1:52 [PATCH v1 net-next] net: phy: mdio_bus: make mdiobus_scan also cover PHY that only talks C45 Voon Weifeng
2019-08-26 18:27 ` Florian Fainelli
2019-08-26 18:54 ` Andrew Lunn
2019-08-27 15:23 ` Voon, Weifeng [this message]
2019-08-27 15:37 ` Florian Fainelli
2019-08-27 15:49 ` Andrew Lunn
2019-08-28 15:41 ` Ong, Boon Leong
2019-08-28 17:00 ` Florian Fainelli
2019-08-28 17:36 ` Voon, Weifeng
2019-08-26 21:28 ` David Miller
2019-08-27 10:25 ` Voon, Weifeng
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