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SubjectRe: [PATCH v2 net] phy: Micrel KSZ8061: link failure after cable connect
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.
> 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).
> When this issue occurs, link is not established. Subsequent cable
> plug/unplug cycles will not correct the issue.
> 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).
> 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")


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