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Thu, 12 Nov 2026 05:23:19 -0800 (PST) Received: from localhost.localdomain ([2a13:e746:396c:c600::31a]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c504a5704c3sm341545966b.26.2026.11.12.05.23.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Nov 2026 05:23:18 -0800 (PST) From: "Kordian Chmielewski (mlody1212)" To: netdev@vger.kernel.org Cc: Florian Fainelli , =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= , bcm-kernel-feedback-list@broadcom.com, Andrew Lunn , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org Subject: Re: [PATCH net 0/7] net: bcm4908_enet: TX ring and DMA fixes Date: Thu, 12 Nov 2026 14:23:08 +0100 Message-ID: <20261112132308.340291-1-kudzo51@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261109235700.2586821-1-kudzo51@gmail.com> References: <20261109235700.2586821-1-kudzo51@gmail.com> X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A correction to the cover letter and to two changelogs: I mixed up what I had seen fail on the hardware with what I had found reading the code. Only patches 1 and 7 come from failures on the hardware. Patch 1 fixes the TX stall under load (seen twice, none in 8 runs with the fix). Patches 2 to 6 come from reading the code and have no reproducer. Patch 7: the skb_over_panic was seen only after I raised the RX channel's MAX_BURST to 32 by hand on a running channel. I tried that again today on my 6.18 tree with the patch: within seconds one frame was longer than the buffer, and it was dropped and counted in rx_length_errors instead of a panic, but the DMA then stalled and the board needed a reboot. With the driver's own value, 8, there were none in about 18 million frames. So patch 7 is hardening and belongs in net-next rather than net. Two changelogs say too much. In patch 3, the TX skbs left on stop are leaked, not freed: the stale descriptors could send buffers nobody freed. In patch 6, I have no test of what the DMA does at a descriptor being refilled. With the patch, a 16-entry RX ring under more traffic than the CPU can take gave no RX or checksum errors in about 14 million frames, but I have not run that without the patch. Also, the panic in patch 7 passed 3388 to skb_put(), so the descriptor said 3392 with the FCS. In my earlier plan mail I wrote that RX buffers were not freed on stop and that RX frames longer than the buffer were passed up. Both were wrong: the RX buffers are freed, only unmapped with a size of 0, and such frames end in skb_over_panic, seen only with the raised burst. I will send a v2 with these fixed. Kordian