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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a82301adesm65720755e9.10.2026.04.30.07.41.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2026 07:41:07 -0700 (PDT) Date: Thu, 30 Apr 2026 15:41:05 +0100 From: David Laight To: KhaiWenTan Cc: anthony.l.nguyen@intel.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, faizal.abdul.rahim@intel.com, hong.aun.looi@intel.com, khai.wen.tan@intel.com, Faizal Rahim Subject: Re: [PATCH iwl-next v4 0/3] igc: add support for forcing link speed without autonegotiation Message-ID: <20260430154105.505739ac@pumpkin> In-Reply-To: <20260428060009.311393-1-khai.wen.tan@linux.intel.com> References: <20260428060009.311393-1-khai.wen.tan@linux.intel.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 28 Apr 2026 14:00:06 +0800 KhaiWenTan wrote: > From: Faizal Rahim > > This series adds support for forcing 10/100 Mb/s link speed via ethtool > when autonegotiation is disabled on the igc driver. I'll ask 'why' ? In particular forcing half/full duplex has always been a very good way of 'breaking' a network connection. It really is much better to restrict the advertised link modes and let the autodetect/autonegotiation logic in the phy/mac do its job. About the only think I can think of is to force 10M HDX when connected to a remote system that supports 10M/100M HDX. In that case you need to send out single link test pulses, not the burst used to identify 100M HDX, or the pattern encoded on the burst used by autonegotiation. But you need to got back to the mid 1990s to find such systems. Anything that supports FDX will do autonegotiation. David > > Changes in v4: > - Validate that autoneg is AUTONEG_ENABLE or AUTONEG_DISABLE early > in igc_ethtool_set_link_ksettings() to avoid passing unexpected > values to igc_handle_autoneg_disabled(). (Simon Horman) > > Changes in v3: > - Modify condition from "if (duplex == DUPLEX_HALF)" to > "if (duplex != DUPLEX_FULL)". (Simon Horman) > > Changes in v2: > - When forcing half-duplex, set hw->fc.requested_mode = igc_fc_none, > since half-duplex cannot support flow control per IEEE 802.3. > (Simon Horman) > - Split the original single patch into three patches for clarity: > patches 1 and 2 are preparatory cleanups; patch 3 carries the > functional change. > > v3 at: > https://patchwork.ozlabs.org/project/intel-wired-lan/cover/20260422155701.7420-1-khai.wen.tan@linux.intel.com/ > > v2 at: > https://patchwork.kernel.org/project/netdevbpf/patch/20260416015520.6090-4-khai.wen.tan@linux.intel.com/ > > v1 at: > https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20260409072747.217836-1-khai.wen.tan@linux.intel.com/ > > Faizal Rahim (3): > igc: remove unused autoneg_failed field > igc: move autoneg-enabled settings into igc_handle_autoneg_enabled() > igc: add support for forcing link speed without autonegotiation > > drivers/net/ethernet/intel/igc/igc_base.c | 35 +++- > drivers/net/ethernet/intel/igc/igc_defines.h | 9 +- > drivers/net/ethernet/intel/igc/igc_ethtool.c | 209 +++++++++++++------ > drivers/net/ethernet/intel/igc/igc_hw.h | 10 +- > drivers/net/ethernet/intel/igc/igc_mac.c | 16 +- > drivers/net/ethernet/intel/igc/igc_main.c | 2 +- > drivers/net/ethernet/intel/igc/igc_phy.c | 65 +++++- > drivers/net/ethernet/intel/igc/igc_phy.h | 1 + > 8 files changed, 257 insertions(+), 90 deletions(-) > > -- > 2.43.0 > >