From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Lunn Subject: Re: [PATCH v2 net] phy: Micrel KSZ8061: link failure after cable connect Date: Fri, 23 Nov 2018 16:00:18 +0100 Message-ID: <20181123150018.GA30913@lunn.ch> References: <1542965762-26822-1-git-send-email-alexander.onnasch@landisgyr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: Florian Fainelli , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: "Onnasch, Alexander (EXT)" Return-path: Content-Disposition: inline In-Reply-To: <1542965762-26822-1-git-send-email-alexander.onnasch@landisgyr.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, Nov 23, 2018 at 09:36:11AM +0000, Onnasch, Alexander (EXT) wrote: > With Micrel KSZ8061 PHY, the link may occasionally not come up after > Ethernet cable connect. The vendor's (Microchip, former Micrel) errata > sheet 80000688A.pdf describes the problem and possible workarounds in > detail, see below. > The patch implements workaround 1, which permanently fixes the issue. > > DESCRIPTION > Link-up may not occur properly when the Ethernet cable is initially > connected. This issue occurs more commonly when the cable is connected > slowly, but it may occur any time a cable is connected. This issue occurs > in the auto-negotiation circuit, and will not occur if auto-negotiation > is disabled (which requires that the two link partners be set to the > same speed and duplex). > > END USER IMPLICATIONS > When this issue occurs, link is not established. Subsequent cable > plug/unplug cycles will not correct the issue. > > WORK AROUND > There are four approaches to work around this issue: > 1. This issue can be prevented by setting bit 15 in MMD device address 1, > register 2, prior to connecting the cable or prior to setting the > Restart Auto-Negotiation bit in register 0h.The MMD registers are > accessed via the indirect access registers Dh and Eh, or via the Micrel > EthUtil utility as shown here: > • If using the EthUtil utility (usually with a Micrel KSZ8061 > Evaluation Board), type the following commands: > > address 1 > > mmd 1 > > iw 2 b61a > • Alternatively, write the following registers to write to the > indirect MMD register: > Write register Dh, data 0001h > Write register Eh, data 0002h > Write register Dh, data 4001h > Write register Eh, data B61Ah > 2. The issue can be avoided by disabling auto-negotiation in the KSZ8061, > either by the strapping option, or by clearing bit 12 in register 0h. > Care must be taken to ensure that the KSZ8061 and the link partner > will link with the same speed and duplex. Note that the KSZ8061 > defaults to full-duplex when auto-negotiation is off, but other > devices may default to half-duplex in the event of failed > auto-negotiation. > 3. The issue can be avoided by connecting the cable prior to powering-up > or resetting the KSZ8061, and leaving it plugged in thereafter. > 4. If the above measures are not taken and the problem occurs, link can > be recovered by setting the Restart Auto-Negotiation bit in > register 0h, or by resetting or power cycling the device. Reset may > be either hardware reset or software reset (register 0h, bit 15). > > PLAN > This errata will not be corrected in a future revision. > > Signed-off-by: Alexander Onnasch > Reviewed-by: Andrew Lunn > --- Hi Alexander Thanks for correctly formatting the commit message, etc. Fixes: 7ab59dc15e2f ("drivers/net/phy/micrel_phy: Add support for new PHYs") Andrew