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AJvYcCWFzEikbACIcLbO537Grl1XLksiBe5TqGDPNghk07OyS5ZD0fUtF6LaqVbDAD/3sOYhZfR279g2DNEFmaLIt/fnCLyO5HNx9byJexrx1Q== X-Gm-Message-State: AOJu0YyHJHwSMiZDtecR6I8W+rQMGdRQWacA/vSNE0fq1wBNeG8P0hO+ zgQ7ERwLzgoQzRKiSMPPnkPD5ifgp8iEpBP/vaFF7mS1o2unMcJlztravtmNgcQ= X-Google-Smtp-Source: AGHT+IHGDJwgvu27ZoxkF/Iz1RMQROmHIKs8TmuQAxLdh09B6CWq3+c9Jjh5o5EFESeTZQUuMmrUsQ== X-Received: by 2002:a05:6358:418f:b0:1ac:660a:8a69 with SMTP id e5c5f4694b2df-1af3baf62a6mr2337848555d.18.1723020236454; Wed, 07 Aug 2024 01:43:56 -0700 (PDT) Received: from dev-mattc2.dev.purestorage.com ([208.88.159.128]) by smtp.googlemail.com with ESMTPSA id 41be03b00d2f7-7b7654bf852sm6742435a12.90.2024.08.07.01.43.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Aug 2024 01:43:55 -0700 (PDT) From: Matthew W Carlis To: helgaas@kernel.org Subject: PCI: Work around PCIe link training failures Date: Wed, 7 Aug 2024 02:43:48 -0600 Message-Id: <20240807084348.12304-1-mattc@purestorage.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20240806193622.GA74589@bhelgaas> References: <20240806193622.GA74589@bhelgaas> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-pci@vger.kernel.org, mahesh@linux.ibm.com, edumazet@google.com, oohall@gmail.com, sr@denx.de, leon@kernel.org, linux-rdma@vger.kernel.org, kuba@kernel.org, pabeni@redhat.com, wilson@tuliptree.org, linuxppc-dev@lists.ozlabs.org, npiggin@gmail.com, alex.williamson@redhat.com, bhelgaas@google.com, mika.westerberg@linux.intel.com, david.abdurachmanov@gmail.com, saeedm@nvidia.com, linux-kernel@vger.kernel.org, lukas@wunner.de, netdev@vger.kernel.org, mattc@purestorage.com, pali@kernel.org, davem@davemloft.net, macro@orcam.me.uk Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tues, 06 Aug 2024 Bjorn Helgaas wrote: > it does seem like this series made wASMedia ASM2824 work better but > caused regressions elsewhere, so maybe we just need to accept that > ASM2824 is slightly broken and doesn't work as well as it should. One of my colleagues challenged me to provide a more concrete example where the change will cause problems. One such configuration would be not implementing the Power Controller Control in the Slot Capabilities Register. Then, Powering off the slot via out-of-band interfaces would result in the kernel forcing the DSP to Gen1 100% of the time as far as I can tell. The aspect of this force to Gen1 that is the most concerning to my team is that it isn't cleaned up even if we replaced the EP with some other EP. I was curious about the PCIe devices mentioned in the commit because I look at crazy malfunctioning devices too often so I pasted the following: "Delock Riser Card PCI Expres 41433" into Google. I'm not really a physical layer guy, but is it possible that the reported issue be due to signal integrity? I'm not sure if sending PCIe over a USB cable is "reliable". I've never worked with an ASMedia switch and don't have a reliable way to reproduce anything like the interaction between the two device at hand. As much as I hate to make the request my thinking is that the patch should be reverted until there is a solution that doesn't leave the link forced to Gen1 forever for every EP thereafter. - Matt