From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 41s3pZ3dWvzDr4h for ; Fri, 17 Aug 2018 10:23:50 +1000 (AEST) Message-ID: <16fa7682a17785cd2580a12fed60e237f6f98826.camel@kernel.crashing.org> Subject: [PATCH] powerpc/powernv/pci: Work around races in PCI bridge enabling From: Benjamin Herrenschmidt To: linuxppc-dev@lists.ozlabs.org Cc: Michael Ellerman Date: Fri, 17 Aug 2018 10:23:42 +1000 Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , The generic code is race when multiple children of a PCI bridge try to enable it simultaneously. This leads to drivers trying to access a device through a not-yet-enabled bridge, and this EEH errors under various circumstances when using parallel driver probing. There is work going on to fix that properly in the PCI core but it will take some time. x86 gets away with it because (outside of hotplug), the BIOS enables all the bridges at boot time. This patch does the same thing on powernv by enabling all bridges that have child devices at boot time, thus avoiding subsequent races. It's suitable for backporting to stable and distros, while the proper PCI fix will probably be significantly more invasive. Signed-off-by: Benjamin Herrenschmidt CC: stable@vger.kernel.org --- diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c index 70b2e1e0f23c..0975b0aaf210 100644 --- a/arch/powerpc/platforms/powernv/pci-ioda.c +++ b/arch/powerpc/platforms/powernv/pci-ioda.c @@ -3368,12 +3368,52 @@ static void pnv_pci_ioda_create_dbgfs(void) #endif /* CONFIG_DEBUG_FS */ } +static void pnv_pci_enable_bridge(struct pci_bus *bus) +{ + struct pci_dev *dev = bus->self; + struct pci_bus *child; + + /* Empty bus ? bail */ + if (list_empty(&bus->devices)) + return; + + /* + * If there's a bridge associated with that bus enable it. This works + * around races in the generic code if the enabling is done during + * parallel probing. This can be removed once those races have been + * fixed. + */ + if (dev) { + int rc = pci_enable_device(dev); + if (rc) + pci_err(dev, "Error enabling bridge (%d)\n", rc); + pci_set_master(dev); + } + + /* Perform the same to child busses */ + list_for_each_entry(child, &bus->children, node) + pnv_pci_enable_bridge(child); +} + +static void pnv_pci_enable_bridges(void) +{ + struct pci_controller *hose; + struct pnv_phb *phb; + struct pci_bus *bus; + struct pci_dev *pdev; + + list_for_each_entry(hose, &hose_list, list_node) + pnv_pci_enable_bridge(hose->bus); +} + static void pnv_pci_ioda_fixup(void) { pnv_pci_ioda_setup_PEs(); pnv_pci_ioda_setup_iommu_api(); pnv_pci_ioda_create_dbgfs(); + pnv_pci_enable_bridges(); + #ifdef CONFIG_EEH pnv_eeh_post_init(); #endif