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Hagan" To: CC: , , , , , , , , , , Subject: Re: [PATCH iwl-net] e1000e: fix flow control stuck off after link partner reset Date: Sat, 26 Sep 2026 13:27:44 +0000 Message-ID: <20260926132744.24777-1-hagan@amazon.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <42cccecf-ff14-41e1-811d-e5a44f3d1aab@gmail.com> References: <42cccecf-ff14-41e1-811d-e5a44f3d1aab@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: EX19D031UWA004.ant.amazon.com (10.13.139.19) To EX19D001UWA001.ant.amazon.com (10.13.138.214) 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? 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): --- 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. + */ + 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; + } } }