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[2003:ea:8f29:6000:f482:8f51:2469:4533]) by smtp.googlemail.com with ESMTPSA id i1sm4125579wrq.89.2020.03.19.10.04.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Mar 2020 10:04:54 -0700 (PDT) Subject: Re: [PATCH net-next 1/3] net: phy: add and use phy_check_downshift To: Florian Fainelli , Russell King - ARM Linux admin , Andrew Lunn Cc: David Miller , "netdev@vger.kernel.org" References: <6e4ea372-3d05-3446-2928-2c1e76a66faf@gmail.com> <20200318232159.GA25745@shell.armlinux.org.uk> <20200319112535.GD25745@shell.armlinux.org.uk> <20200319130429.GC24972@lunn.ch> <20200319135800.GE25745@shell.armlinux.org.uk> <92689def-4bbf-8988-3137-f3cfb940e9fc@gmail.com> <5e5c647b-f05d-d9d3-0554-68af99ee3f55@gmail.com> From: Heiner Kallweit Message-ID: <82c01854-4571-4e4f-680d-316f7cd0870f@gmail.com> Date: Thu, 19 Mar 2020 18:04:51 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <5e5c647b-f05d-d9d3-0554-68af99ee3f55@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 19.03.2020 17:55, Florian Fainelli wrote: > Le 2020-03-19 à 09:36, Heiner Kallweit a écrit : >> *Downshift reporting/warning* >> In most cases downshift is caused by some problem with the cabling. >> Users like the typical Ubuntu user in most cases are not familiar >> with the concept of PHY downshift and what causes a downshift. >> Therefore it's not sufficient to just report a downshift, we have >> to provide the user with a hint what to do. >> Adding the "downshifted" info to phy_print_status() is a good idea, >> however I'd see it as an optional addition to the mentioned hint >> to the user what to do. >> The info "unknown downshift" IMO would just cause confusion. If we >> have nothing to say, then why say something. Also users may interpret >> "unknown" as "there's something wrong". > > Ideally we would also have support for cable testing as well which would > allow users to know what to do next to figure out why their link speed > is not what they had hoped for. That does require a specific PHY driver > though as there is no standard way to obtain that information. > > FWIW, a bunch of drivers like tg3, e1000e, igc and possibly others do > report when downshifting occurs, of course not all of those in that list > use the PHY library. > Yes, a direct link to cable testing would be nice. With the new netlink-based ethtool support for cable testing comes closer. AFAIK Andrew is evaluating what an API could look like. However for the time being I think a downshift warning in phylib would be helpful to explain to the user: Check your damned cabling instead of spamming support forums with blaming the network driver or any other piece of software or hardware.