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Tue, 16 Jun 2026 09:16:29 -0700 (PDT) Received: from [192.168.0.128] ([98.97.36.235]) by smtp.googlemail.com with ESMTPSA id 5a478bee46e88-3081eb95450sm23977823eec.28.2026.06.16.09.16.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jun 2026 09:16:27 -0700 (PDT) Message-ID: <06d8c98da24e80d148ede4e933bb621c5515a7a2.camel@gmail.com> Subject: Re: Ethtool : PRBS feature From: Alexander H Duyck To: "Das, Shubham" , Andrew Lunn Cc: "netdev@vger.kernel.org" , "mkubecek@suse.cz" , "D H, Siddaraju" , "Chintalapalle, Balaji" Date: Tue, 16 Jun 2026 09:14:55 -0700 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2026-06-16 at 12:14 +0000, Das, Shubham wrote: > Hi Andrew, >=20 > Thanks for the feedback. >=20 > Yes, for multi-lane ports we can accept the lane number as an argument li= ke: >=20 > ethtool --phy-test eth1 lane 0 tx-prbs prbs7 > ethtool --phy-test eth2 lane 0 rx-prbs prbs7 >=20 > We referred to "Lee Trager's" "Open-Source Tooling for PHY Management and= Testing" session: > https://netdevconf.info/0x19/sessions/talk/open-source-tooling-for-phy-ma= nagement-and-testing.html?. > We have been trying to reach "Lee Trager" to seek more input, latest upda= te on the approach and understand if there is a parallel effort in active s= o we can collaborate. > If you can, please help me connect with "Lee Trager" and others who expre= ssed interest in Ethernet PRBS. We are happy to align and start implementat= ion. >=20 You aren't going to have much luck if you are trying to reach out via his Meta address as he has moved onto Nvidia so he is no longer working on the fbnic driver. As far as the work done most of it was internal and making use of debugfs. I don't believe any of the work for fbnic began to approach the suggested methods for upstreamming the feature as Lee had been pulled into other efforts. > About standardizing across other bus like PCIe and USB, I had a quick dis= cussion with our internal designers, but I didn't observe any such SW-level= config knobs interest.=20 > Looks like Ethernet has clear interest and we are joining that Ethernet P= RBS community too. I think it largely depends on what your implementation looks like. The point being made was that many of the SerDes PHYs out there are capable of use in multiple applications. So instead of being a networking device you would be looking at a SerDes PHY such as those in "/drivers/phy/". Also do you know what layer in the PHY you are injecting this PRBS at? I would be curious if this is PCS or at the PMD level? If you are referring to the PCS level then yes, it would make sense to have it in the networking subsystem as the PCS at this point is more a netdev specific set of drivers, see "/drivers/net/pcs/". In the case of the PMD that is where things get a bit more interesting. There is an IEEE c45 register definition that includes PRBS testing registers, however in the case of our implementation the PMD doesn't follow that specification and follows more the "/drivers/phy/" model. > Ethernet PRBS configuration and diagnostics support is well established a= nd already widely used in existing Ethernet SERDES deployments. > We think Ethernet is the most natural starting point within netdev, as it= aligns with current driver practice and existing validation workflows.=C2= =A0 The problem is many of these parts used as an Ethernet Serdes PMD are really a multiuse part. So for example in the case of the hardware in FBNIC we use the same part on the Ethernet PHY as we do for the PCIe Gen5 PHY. The complication in our case is that both are buried behind our FW due to the fact that both are shared between slices. However for testing purposes and such we could look at disabling the odd slices to essentially unshare the hardware if you need another platform to test something like this with.