RE: Support for Forcing Speed/Duplex/Autoneg on i225 with DPDK igc Driver

[Renata Saiakhova <renata.saiakhova@ekinops.com>]

Hi all, hi Ivan and Stephen,

Thank you for your comments and clarifications.

Indeed, the correct way to set speed and autoneg for a DPDK port is by configuring the link_speeds field in the struct rte_eth_conf passed to rte_eth_dev_configure().

However, after reviewing the openvswitch (version 3.3.2) code, I found that OVS does not currently expose any mechanism to set these Layer 1 attributes (speed, autoneg or duplex) via ovs-vsctl or OVSDB. The relevant fields in rte_eth_conf are not settable through OVS configuration, and there is no code to parse or apply such options from the OVSDB or command line. To support this, OVS would need to be extended to parse these options and set the corresponding fields in rte_eth_conf before calling rte_eth_dev_configure().

So, at present, there is no way to configure these parameters through OVS without adding custom code. However, for our customer we need to add this implementation. Do you think that the community would benefit from this implementation? 

Kind regards,
Renata Saiakhova

-----Original Message-----
From: Stephen Hemminger <stephen@networkplumber.org> 
Sent: Saturday, 2 August 2025 00:02
To: Ivan Malov <ivan.malov@arknetworks.am>
Cc: Renata Saiakhova <renata.saiakhova@ekinops.com>; users@dpdk.org
Subject: Re: Support for Forcing Speed/Duplex/Autoneg on i225 with DPDK igc Driver

On Fri, 1 Aug 2025 17:10:44 +0400 (+04)
Ivan Malov <ivan.malov@arknetworks.am> wrote:

> Hi Renata,
> 
> On Fri, 1 Aug 2025, Renata Saiakhova wrote:
> 
> > 
> > Hi all,
> > 
> > I’m trying to configure Layer 1 attributes (speed, duplex, and autonegotiation) for Intel i225 interfaces in both kernel and DPDK modes, and I’ve run into some issues.
> > 
> > In kernel driver mode, I normally use: “ethtool -s eth5 speed 100 duplex half autoneg off”.
> > 
> > However, this results in the kernel message: “igc 0000:04:00.0 eth5: Force mode currently not supported”.
> > 
> >  
> > 
> > When the interface is bound to DPDK and connected to an OVS bridge, I configure it like this:
> > 
> > ovs-vsctl set Interface 1.extra2 \
> > 
> >   type=dpdk \
> > 
> >   options:dpdk-devargs=0000:04:00.0 \
> > 
> >   options:dpdk-speed=100 \
> > 
> >   options:dpdk-autoneg=false \
> > 
> >   options:dpdk-duplex=half
> > 
> > This should pass the speed/autoneg/duplex settings to the igc DPDK driver via devargs.  
> 
> Should it? Even if these were on the list of supported devargs for the 
> PMD in question, they would belong in comma-separated tokens after '0000:04:00.0'.
> I don't see these to be parsed in the OvS, neither do I see such in the PMD.
> 
> Or are you looking at some custom OvS version?
> 
> > 
> > However, it appears these options are not applied — the interface 
> > continues to negotiate its settings as usual, and I can’t find any code in the igc DPDK driver that processes these devargs parameters.
> 
> If these were passed via 'dpdk-devargs', the PMD would've complained perhaps.
> Being passed as OvS's own options, they're likely just ignored by the OvS.
> 
> > 
> > Is support for forced speed/duplex/autoneg available at all for i225 in DPDK (or even kernel) mode? Or is this a hardware limitation?  
> 
> As per [1], 'forced' mode may not be supported in the DPDK PMD. But 
> the code suggests one can possibly try to pass, say, 
> 'RTE_ETH_LINK_SPEED_100M_HD', without being accompanied by neither 
> 'AUTONEG' nor 'FIXED', but that would still come as 'advertised' mode, not a 'forced' one. I may be wrong, though.
> 
> [1] 
> https://github.com/DPDK/dpdk/blob/1b3bf1128d9bda5595861814792f74b8f571
> 60c8/drivers/net/igc/igc_ethdev.c#L1088
> 
> > 
> > Any insight, documentation pointers, or confirmation of support status especially in case of DPDK mode would be greatly appreciated.  
> 
> I take it OvS most likely needs to be augmented with extra code to 
> recognise such options and translate those into DPDK link settings. 
> For an example of how a DPDK application can do that, one should refer to 'test-pmd' implementation.
> 
> Thank you.
> 
> > 
> > Best regards,
> > 
> >  
> > 
> >  
> > 
> > Renata Saiakhova
> > SW ARCHITECT
> > renata.saiakhova@ekinops.com
> > Tel: +32 16 799 970
> > 
> > [logo_96dpi.gif]
> > 
> > [current.png]
> > 
> >  
> > 
> > 
> >  

Use of driver specific devargs is strongly discouraged.
There is link_speeds in rte_eth_conf passed to rte_eth_dev_configure() which is the correct way to set fixed speed. It maybe that the driver doesn't interpret it correctly?