Date: Wed, 14 Dec 2011 02:16:57 +0100 From: Marius Strobl <marius@alchemy.franken.de> To: YongHyeon PYUN <pyunyh@gmail.com> Cc: FreeBSD Net <freebsd-net@freebsd.org>, Stefan Bethke <stb@lassitu.de> Subject: Re: "ifconfig media off"? Message-ID: <20111214011657.GH36635@alchemy.franken.de> In-Reply-To: <20111213185348.GA7546@michelle.cdnetworks.com> References: <600A8C6C-DAB4-4E22-A034-38224017166B@lassitu.de> <20111213025041.GF3705@michelle.cdnetworks.com> <45B0B859-207C-4F02-A28F-7E34B775A273@lassitu.de> <20111213185348.GA7546@michelle.cdnetworks.com>
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On Tue, Dec 13, 2011 at 10:53:48AM -0800, YongHyeon PYUN wrote:
> On Tue, Dec 13, 2011 at 11:04:51AM +0100, Stefan Bethke wrote:
> > Am 13.12.2011 um 03:50 schrieb YongHyeon PYUN:
> >
> > > On Tue, Dec 13, 2011 at 12:56:22AM +0100, Stefan Bethke wrote:
> > >> I'm currently writing a driver to configure an ethernet switch chip (see TL-WR1043ND on -embedded).
> > >>
> > >> I noticed that there doesn't seem to be a way to power down a phy right now through the ifconfig media command.
> > >>
> > >> Would there be objections to extend the media subtype definitions to include an "off", "poweroff" or "down" media subtype, and add code to the relevant phy drivers to power down the phy for this media subtype?
> > >>
> > >> The difference between media subtype "none" and this new one would be that there will be no link, even if there is a physical connection. With media subtype "none", a 10 MBit/s half-duplex connection is established, potentially confusing the remote end about the availability of this link. On the local side, the link is down, so no packets are exchanged.
> > >>
> > >
> > > I think "none" means "isolated" so should have no established link
> > > and probably you can also power down the PHY.
> > > I vaguely guess the PHY of switch chip does not correctly support
> > > isolated mode so you may have wanted to power down.
> >
> >
> > After looking at the code a bit more, I think the common code just doesn't set the BMCR_PDOWN (but clears it when bringing up the PHY).
> >
>
> Yes, and most PHYs could be powered down when BMCR_ISO is chosen.
> I'm not sure whether this could be applied to hardwares that
> support multiple PHYs(i.e. internal and external transceivers)
> though. Marius may have some opinions on this(CCed).
> However powering down PHY with BMCR_ISO looks natural to me.
>
> > Index: sys/dev/mii/mii_physubr.c
> > ===================================================================
> > --- sys/dev/mii/mii_physubr.c (revision 228402)
> > +++ sys/dev/mii/mii_physubr.c (working copy)
> > @@ -58,7 +58,7 @@
> > */
> > static const struct mii_media mii_media_table[MII_NMEDIA] = {
> > /* None */
> > - { BMCR_ISO, ANAR_CSMA,
> > + { BMCR_ISO | BMCR_PDOWN, ANAR_CSMA,
> > 0, },
> >
> > /* 10baseT */
> >
> > I've opened kern/163240.
> > http://www.freebsd.org/cgi/query-pr.cgi?pr=163240
I don't think powering down the PHY along with IFM_NONE especially
in that way is a good idea for several reasons:
- It's incomplete as not all PHY drivers use mii_phy_add_media()/
mii_phy_setmedia().
- Even for those that do IFM_NONE isn't added when the PHY driver
sets MIIF_NOISOLATE (for some PHYs BMCR_ISO either just doesn't
work as especially the built-in ones probably have been designed
with only single-PHY configurations in mind or even wedges the
chip up to the point that even a reset doesn't get it working
again). In general though, BMCR_ISO and BMCR_PDOWN are orthogonal
(even in IEEE 802.3-2008 as far as I can see), i.e. while BMCR_ISO
might be broken, BMCR_PDOWN could work (actually I'd expect
BMCR_PDOWN to be less fragile than BMCR_ISO).
- There should be a way to let a PHY driver do something different
than setting BMCR_PDOWN when it's told to power down as f.e. at
least some Broadcom PHYs support a "super isolation" mode.
- As you already mentioned in general there can be multiple PHYs
on one MII bus and I'd expect "power down that interface" to
mean to power all of them down (granted, MACs with multiple
PHYs are rather uncommon in reality but they do exist, f.e.
Allied Telesis has several card models that use two PHYs per
MAC).
In generall I agree that there should be a way to power down PHYs
though. While there might be some merit in additionally adding that
as a media option I think that the most intuitive way would be for
`ifconfig foo0 down` to also power down the PHYs on that interface.
In order implement that the basic way seems to be to make the
various foo_stop() methods of MAC drivers to call mii_down() (as
in NetBSD) and to make mii_phy_down() (or a replacement) actually
do something, with PHY drivers being allowed to opt-out with
something like a MIIF_NOPOWERDOWN. What I'm not sure about is how
to implement power down in the individual drivers while keeping
code duplication for the common case low, i.e. I'm not sure whether
the NetBSD way of having a MII_DOWN case in the service routines
is the way to go.
Is there something in the rc.d scripts that downs network
interfaces on shutdown that could interfere with WOL when we
power down the PHYs?
Marius
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