From: Andrew Lunn <andrew@lunn.ch>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Heiner Kallweit <hkallweit1@gmail.com>,
Florian Fainelli <f.fainelli@gmail.com>,
David Miller <davem@davemloft.net>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH net-next 1/3] net: phy: add and use phy_check_downshift
Date: Thu, 19 Mar 2020 10:06:40 +0100 [thread overview]
Message-ID: <20200319090640.GB20761@lunn.ch> (raw)
In-Reply-To: <20200318232159.GA25745@shell.armlinux.org.uk>
On Wed, Mar 18, 2020 at 11:21:59PM +0000, Russell King - ARM Linux admin wrote:
> On Wed, Mar 18, 2020 at 10:29:01PM +0100, Heiner Kallweit wrote:
> > So far PHY drivers have to check whether a downshift occurred to be
> > able to notify the user. To make life of drivers authors a little bit
> > easier move the downshift notification to phylib. phy_check_downshift()
> > compares the highest mutually advertised speed with the actual value
> > of phydev->speed (typically read by the PHY driver from a
> > vendor-specific register) to detect a downshift.
>
> My personal position on this is that reporting a downshift will be
> sporadic at best, even when the link has negotiated slower.
>
> The reason for this is that either end can decide to downshift. If
> the remote partner downshifts, then the local side has no idea that
> a downshift occurred, and can't report that the link was downshifted.
>
> So, is it actually useful to report these events?
It is better than nothing.
We get one end reporting a downshift, and the peer reporting a slower
than expected negotiated link speed. Combined that gives a good clue.
I also want to start merging cable diagnostics soon. There is enough
of netlink ethtool in place to allow this.
And the same netlink ethool will allow us to extend the API and report
downshift in the ethtool output, not just a kernel message.
Andrew
next prev parent reply other threads:[~2020-03-19 9:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-18 21:27 [PATCH net-next 0/3] net: phy: add and use phy_check_downshift Heiner Kallweit
2020-03-18 21:29 ` [PATCH net-next 1/3] " Heiner Kallweit
2020-03-18 23:21 ` Russell King - ARM Linux admin
2020-03-19 7:30 ` Heiner Kallweit
2020-03-19 11:25 ` Russell King - ARM Linux admin
2020-03-19 13:04 ` Andrew Lunn
2020-03-19 13:58 ` Russell King - ARM Linux admin
2020-03-19 16:36 ` Heiner Kallweit
2020-03-19 16:55 ` Florian Fainelli
2020-03-19 17:04 ` Heiner Kallweit
2020-03-19 17:08 ` Russell King - ARM Linux admin
2020-03-20 8:07 ` Heiner Kallweit
2020-03-19 9:06 ` Andrew Lunn [this message]
2020-03-19 9:10 ` Andrew Lunn
2020-03-18 21:29 ` [PATCH net-next 2/3] net: phy: marvell: remove downshift warning now that phylib takes care Heiner Kallweit
2020-03-18 21:31 ` [PATCH net-next 3/3] net: phy: aquantia: " Heiner Kallweit
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200319090640.GB20761@lunn.ch \
--to=andrew@lunn.ch \
--cc=davem@davemloft.net \
--cc=f.fainelli@gmail.com \
--cc=hkallweit1@gmail.com \
--cc=linux@armlinux.org.uk \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).