On October 17, 2016 12:31:54 AM PDT, Raju Lakkaraju
>Thank you for code review and comments.
>On Fri, Oct 14, 2016 at 02:12:32PM +0200, Andrew Lunn wrote:
>> EXTERNAL EMAIL
>> On Fri, Oct 14, 2016 at 05:10:32PM +0530, Raju Lakkaraju wrote:
>> > From: Raju Lakkaraju <raju.lakkar...@microsemi.com>
>> > For operation in cabling environments that are incompatible with
>> > 1000BAST-T, VSC8531 device provides an automatic link speed
>> > downshift operation. When enabled, the device automatically changes
>> > its 1000BAST-T auto-negotiation to the next slower speed after
>> > a configured number of failed attempts at 1000BAST-T.
>> > This feature is useful in setting up in networks using older cable
>> > installations that include only pairs A and B, and not pairs C and
>> Any reason not to just turn this on by default when auto-neg is
>Downshift can enable by default when auto-neg enabled. This is good
>But we would like to provide option to customer can choose whether this
>feature need to enable or disable and also configure failure attempts.
>Do you have any other suggestion how to configure failure attempts?
Is the speed downshift feature similar to what Intel and Broadcom refer to as
wirespeed? I have seen cases with Broadcom PHYs where we had to turn such a
feature on to allow auto-negotiation to complete with 4-wire cables, but this
had the downside of impacting normal autoneg, so it is left disabled.
I would expect the number of customers using this feature to be fairly limited,
so having a tunable to turn this downshift on/off may be acceptable. Ethtool
supports a number of tunable parameters now (such as rx_copybreak), there may
be room for using something similar for boolean flags like these.