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([2600:6c5c:6b00:316::23]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3475546b1aesm864022eec.4.2026.09.27.09.26.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 27 Sep 2026 09:26:41 -0700 (PDT) Message-ID: <274e9217-834f-43f1-8d71-e64b12052fff@gmail.com> Date: Sun, 27 Sep 2026 12:26:38 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH iwl-net] e1000e: fix flow control stuck off after link partner reset To: "Craig I. Hagan" Cc: andrew+netdev@lunn.ch, anthony.l.nguyen@intel.com, davem@davemloft.net, edumazet@google.com, intel-wired-lan@lists.osuosl.org, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, przemyslaw.kitszel@intel.com References: <42cccecf-ff14-41e1-811d-e5a44f3d1aab@gmail.com> <20260926132744.24777-1-hagan@amazon.com> Content-Language: en-US From: Matt Vollrath In-Reply-To: <20260926132744.24777-1-hagan@amazon.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/26/26 09:27, Craig I. Hagan wrote: > On 2026-09-24, Matt Vollrath wrote: >> I didn't try your patch, but there's a four line fix. Where the watchdog >> resets just the PHY when the MAC exits DMoff state, set FLAG_RESTART_NOW >> instead of resetting the PHY, then goto link_up. This works for me at >> both 1500 and 9000 MTU. > > Thanks Matt, > I've tested this approach on two I219-LM boxes, each attached to a different switch: > one a TP-Link TL-SG108PE V3, and the other a Cisco Catalyst 9200. > > On the Cisco with jumbo frames, I'm seeing, via a diagnostic message, that > the fix appears to fire and work. I have also noticed that I no longer see > it on every boot, but this may be correct as I've not seen traffic stalls. > > With 1500 mtu, I'm seeing it engage fairly regularly with the TP-Link but > not the Cisco. I'm guessing it is related to how the Cisco negotiates. In both cases > traffic doesn't seem to stall. > > I think you are correct about flow control being a red herring since > both switches advertise no pause (Flow Control: None) before and after > recovery. > > I'd like to drop my patch in favour of your fix. > > How should I proceed, should I propose a patch with suggested-by you, or with your authorship and > tested by me? Feel free to add: Suggested-by: Matt Vollrath > > For completeness, here is the diff I tested (I added an e_info so I could see it fire on the > test rig; happy to drop that line - it isn't needed for the fix): I would drop the e_info. > > > > --- a/drivers/net/ethernet/intel/e1000e/netdev.c > +++ b/drivers/net/ethernet/intel/e1000e/netdev.c > @@ -5254,9 +5254,16 @@ > usleep_range(10000, 20000); > pcim_state = er32(STATUS); > > - /* Checking if MAC exited DMoff state */ > - if (!(pcim_state & E1000_STATUS_PCIM_STATE)) > - e1000_phy_hw_reset(&adapter->hw); > + /* Checking if MAC exited DMoff state. A bare > + * PHY reset here does not re-run the jumbo > + * workaround (e1000_lv_jumbo_workaround_ich8lan), > + * so request a full reset instead, which does. > + */ My two cents is that this comment is over-specific. In most places a bare PHY reset is not used, so the transition is toward less exceptional. > + if (!(pcim_state & E1000_STATUS_PCIM_STATE)) { > + e_info("full reset on DMoff exit to restore jumbo-frame configuration\n"); > + adapter->flags |= FLAG_RESTART_NOW; > + goto link_up; > + } > } > } >