On Mon, Mar 18, 2024 at 2:42 PM Stephen Hemminger <step...@networkplumber.org> wrote: > > On Mon, 18 Mar 2024 14:26:33 -0700 > Damodharam Ammepalli <damodharam.ammepa...@broadcom.com> wrote: > > > On Mon, Mar 18, 2024 at 7:56 AM Thomas Monjalon <tho...@monjalon.net> wrote: > > > > > > 12/03/2024 08:52, Dengdui Huang: > > > > Some speeds can be achieved with different number of lanes. For example, > > > > 100Gbps can be achieved using two lanes of 50Gbps or four lanes of > > > > 25Gbps. > > > > When use different lanes, the port cannot be up. > > > > > > I'm not sure what you are referring to. > > > I suppose it is not PCI lanes. > > > Please could you link to an explanation of how a port is split in lanes? > > > Which hardware does this? > > > > > > > > > > > This is a snapshot of 100Gb that the latest BCM576xx supports. > > 100Gb (NRZ: 25G per lane, 4 lanes) link speed > > 100Gb (PAM4-56: 50G per lane, 2 lanes) link speed > > 100Gb (PAM4-112: 100G per lane, 1 lane) link speed > > > > Let the user feed in lanes=< integer value> and the NIC driver decides > > the matching combination speed x lanes that works. In future if a new speed > > is implemented with more than 8 lanes, there wouldn't be a need > > to touch this speed command. Using separate lane command would > > be a better alternative to support already shipped products and only new > > drivers would consider this lanes configuration, if applicable. > > > > The DPDK does not need more driver specific knobs. > Shouldn't the PMD be able to auto negotiate the speed? Yes. Its possible to auto negotiate. And that's the default. Even for the lane count, a default number can be arrived at.
> What does Linux do? ethtool has been extended a while ago to allow configuring the number of lanes along with speed and other settings. But as usual, autoneg is possible.
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