From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: "Madalin Bucur (OSS)" <madalin.bucur@oss.nxp.com>
Cc: "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"davem@davemloft.net" <davem@davemloft.net>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"andrew@lunn.ch" <andrew@lunn.ch>,
"f.fainelli@gmail.com" <f.fainelli@gmail.com>,
"hkallweit1@gmail.com" <hkallweit1@gmail.com>,
"shawnguo@kernel.org" <shawnguo@kernel.org>
Subject: Re: [PATCH 1/6] net: phy: add interface modes for XFI, SFI
Date: Fri, 3 Jan 2020 09:27:18 +0000 [thread overview]
Message-ID: <20200103092718.GB25745@shell.armlinux.org.uk> (raw)
In-Reply-To: <DB8PR04MB69858081021729EC70216BE3EC230@DB8PR04MB6985.eurprd04.prod.outlook.com>
On Fri, Jan 03, 2020 at 07:01:50AM +0000, Madalin Bucur (OSS) wrote:
> > -----Original Message-----
> > From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
> > Sent: Monday, December 23, 2019 2:08 PM
> > To: Madalin Bucur <madalin.bucur@nxp.com>
> > Cc: davem@davemloft.net; netdev@vger.kernel.org; andrew@lunn.ch;
> > f.fainelli@gmail.com; hkallweit1@gmail.com; shawnguo@kernel.org;
> > devicetree@vger.kernel.org
> > Subject: Re: [PATCH 1/6] net: phy: add interface modes for XFI, SFI
> >
> > On Thu, Dec 19, 2019 at 06:32:51PM +0000, Madalin Bucur wrote:
> > > 10GBase-R could be used as a common nominator but just as well 10G and
> > > remove the rest while we're at it. There are/may be differences in
> > > features, differences in the way the HW is configured (the most
> > > important aspect) and one should be able to determine what interface
> > > type is in use to properly configure the HW. SFI does not have the CDR
> > > function in the PMD, relying on the PMA signal conditioning vs the XFI
> > > that requires this in the PMD.
> >
> > I've now found a copy of INF-8077i on the net, which seems to be the
> > document that defines XFI. The definition in there seems to be very
> > similar to SFI in that it is an electrical specification, not a
> > protocol specification, and, just like SFI, it defines the electrical
> > characteristics at the cage, not at the serdes. Therefore, the effects
> > of the board layout come into play to achieve compliance with XFI.
>
> I think we're missing the point here: we need to start from the device
> tree and that is supposed to describe the board, the hardware, not to
> configure the software. Please re-read the paragraph above in this key:
> the device tree needs to describe the HW features, those electrical
> properties you are discussing above. The fact that we use a certain
> protocol over it, by choice in software, does not change the HW and it
> should not change the device tree describing it.
phy_interface_t does *NOT* describe the electrical properties of the
link; it describes the protocol. The protocol for 10GBASE-R, SFI and
XFI are *all* the same. Therefore, phy_interface_t does *not*
distinguish between these.
Yes, DT may need to describe the electrical properties. That needs to
be done independently of the phy_interface_t and therefore phy-mode
definition.
Just like it is done for SATA interfaces that need the eye mask
(electrical properties of the serdes) adjusted for the board.
> > Just like SFI, XFI can be used with multiple different underlying
> > protocols. I quote:
> >
> > "The XFI interface is designed to support SONET OC-192,
> > IEEE.Std-802.3ae, 10GFC and G.709(OTU-2) applications."
> >
> > Therefore, to describe 10GBASE-R as "XFI" is most definitely incorrect.
> > 10GBASE-R is just _one_ protocol that can be run over XFI, but it is
> > not the only one.
>
> Exactly why the chip to chip interface described by the device tree needs
> to be xfi not 10GBASE-R,
Sorry no.
Merely specifying "xfi" does not tell you what you need to do to achieve
XFI compliance at the point defined in INF8077i. Plus, XFI can also be
protocols _other_ than 10GBASE-R.
Claiming that "XFI" properly defines the interface is utter rubbish. It
does not. XFI defines the electrical characteristics *only* and not
the underlying protocol. It is not limited to 10GBASE-R, but includes
other protocols as well.
XFI is not a phy interface type. Sorry.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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next prev parent reply other threads:[~2020-01-03 9:27 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-19 15:21 [PATCH 0/6] Add PHY connection types for XFI and SFI Madalin Bucur
2019-12-19 15:21 ` [PATCH 1/6] net: phy: add interface modes for XFI, SFI Madalin Bucur
2019-12-19 17:28 ` Russell King - ARM Linux admin
2019-12-19 18:32 ` Madalin Bucur
2019-12-19 19:03 ` Russell King - ARM Linux admin
2019-12-19 21:34 ` Madalin Bucur (OSS)
2019-12-19 21:49 ` Russell King - ARM Linux admin
2019-12-20 7:38 ` Madalin Bucur (OSS)
2019-12-20 9:16 ` Russell King - ARM Linux admin
2019-12-20 9:29 ` Andrew Lunn
2019-12-20 9:39 ` Madalin Bucur (OSS)
2019-12-20 10:06 ` Andrew Lunn
2019-12-23 7:50 ` Madalin Bucur (OSS)
2019-12-23 8:26 ` Russell King - ARM Linux admin
2019-12-23 9:57 ` Madalin Bucur (OSS)
2019-12-23 10:57 ` Russell King - ARM Linux admin
2019-12-23 12:07 ` Russell King - ARM Linux admin
2019-12-23 13:46 ` Andrew Lunn
2019-12-23 14:30 ` Russell King - ARM Linux admin
2020-01-03 7:01 ` Madalin Bucur (OSS)
2020-01-03 9:27 ` Russell King - ARM Linux admin [this message]
2020-01-03 9:42 ` Russell King - ARM Linux admin
2020-01-03 12:03 ` Madalin Bucur (OSS)
2020-01-03 12:53 ` Russell King - ARM Linux admin
2020-01-03 13:35 ` Andrew Lunn
2020-01-03 16:21 ` Madalin Bucur (OSS)
2020-01-03 17:17 ` Andrew Lunn
2020-01-06 9:34 ` Madalin Bucur (OSS)
2020-01-03 15:57 ` Madalin Bucur (OSS)
2020-01-03 17:19 ` Russell King - ARM Linux admin
2020-01-06 10:17 ` Madalin Bucur (OSS)
2020-01-06 13:57 ` Andrew Lunn
2020-01-06 15:03 ` Madalin Bucur (OSS)
2019-12-19 15:21 ` [PATCH 2/6] arm64: dts: ls104xardb: set correct PHY interface mode Madalin Bucur
2019-12-19 16:05 ` Andrew Lunn
2019-12-19 18:09 ` Madalin Bucur (OSS)
2019-12-19 15:21 ` [PATCH 3/6] net: fsl/fman: rename IF_MODE_XGMII to IF_MODE_10G Madalin Bucur
2019-12-19 15:21 ` [PATCH 4/6] net: fsl/fman: add support for PHY_INTERFACE_MODE_XFI Madalin Bucur
2019-12-19 15:21 ` [PATCH 5/6] net: fsl/fman: add support for PHY_INTERFACE_MODE_SFI Madalin Bucur
2019-12-19 17:30 ` Russell King - ARM Linux admin
2019-12-19 18:50 ` Madalin Bucur (OSS)
2019-12-19 15:21 ` [PATCH 6/6] net: phy: aquantia: add support for PHY_INTERFACE_MODE_XFI Madalin Bucur
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