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Rozycki" , linux-kernel@vger.kernel.org Cc: Mika Westerberg , =?utf-8?q?Ilpo_J?= =?utf-8?q?=C3=A4rvinen?= Subject: [PATCH 1/2] PCI: Clear LBMS on resume to avoid Target Speed quirk Date: Mon, 29 Jan 2024 13:27:09 +0200 Message-Id: <20240129112710.2852-2-ilpo.jarvinen@linux.intel.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240129112710.2852-1-ilpo.jarvinen@linux.intel.com> References: <20240129112710.2852-1-ilpo.jarvinen@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1789440149273494623 X-GMAIL-MSGID: 1789440149273494623 While a device is runtime suspended along with its PCIe hierarchy, the device could get disconnected. Because of the suspend, the device disconnection cannot be detected until portdrv/hotplug have resumed. On runtime resume, pcie_wait_for_link_delay() is called: pci_pm_runtime_resume() pci_pm_bridge_power_up_actions() pci_bridge_wait_for_secondary_bus() pcie_wait_for_link_delay() Because the device is already disconnected, this results in cascading failures: 1. pcie_wait_for_link_status() returns -ETIMEDOUT. 2. After the commit a89c82249c37 ("PCI: Work around PCIe link training failures"), pcie_failed_link_retrain() spuriously detects this failure as a Link Retraining failure and attempts the Target Speed trick, which also fails. 3. pci_bridge_wait_for_secondary_bus() then calls pci_dev_wait() which cannot succeed (but waits ~1 minute, delaying the resume). The Target Speed trick (in step 2) is only used if LBMS bit (PCIe r6.1 sec 7.5.3.8) is set. For links that have been operational before suspend, it is well possible that LBMS has been set at the bridge and remains on. Thus, after resume, LBMS does not indicate the link needs the Target Speed quirk. Clear LBMS on resume for bridges to avoid the issue. Fixes: a89c82249c37 ("PCI: Work around PCIe link training failures") Reported-by: Mika Westerberg Tested-by: Mika Westerberg Signed-off-by: Ilpo Järvinen --- drivers/pci/pci-driver.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 51ec9e7e784f..05a114962df3 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -574,6 +574,12 @@ static void pci_pm_bridge_power_up_actions(struct pci_dev *pci_dev) { int ret; + /* + * Clear LBMS on resume to avoid spuriously triggering Target Speed + * quirk in pcie_failed_link_retrain(). + */ + pcie_capability_write_word(pci_dev, PCI_EXP_LNKSTA, PCI_EXP_LNKSTA_LBMS); + ret = pci_bridge_wait_for_secondary_bus(pci_dev, "resume"); if (ret) { /*