Hi Andrew and Kishon, On Mon, 2021-02-15 at 15:07 +0100, Andrew Lunn wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you > know the content is safe > > On Mon, Feb 15, 2021 at 05:25:10PM +0530, Kishon Vijay Abraham I > wrote: > > Okay. Is it going to be some sort of manual negotiation where the > > Ethernet controller invokes set_speed with different speeds? Or the > > Ethernet controller will get the speed using some out of band > > mechanism > > and invokes set_speed once with the actual speed? > > Hi Kishon > > There are a few different mechanism possible. > > The SFP has an EEPROM which contains lots of parameters. One is the > maximum baud rate the module supports. PHYLINK will combine this > information with the MAC capabilities to determine the default speed. > > The users can select the mode the MAC works in, e.g. 1000BaseX vs > 2500BaseX, via ethtool -s. Different modes needs different speeds. > > Some copper PHYs will change there host side interface baud rate when > the media side interface changes mode. 10GBASE-X for 10G copper, > 5GBase-X for 5G COPPER, 2500Base-X for 2.5G copper, and SGMII for > old school 10/100/1G Ethernet. > > Mainline Linux has no support for it, but some 'vendor crap' will do > a > manual negotiation, simply trying different speeds and see if the > SERDES establishes link. There is nothing standardised for this, as > far as i know. > > Andrew
Yes, in case I mention the only way to ensure communication is human intervention to set the speed to the highest common denominator. BR Steen
