| Message ID | 20180503223127.GB15790@bhelgaas-glaptop.roam.corp.google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
Le 04/05/2018 00:31, Bjorn Helgaas a écrit : > [+cc LKML] > > On Thu, May 03, 2018 at 12:40:27PM +0000, Gilles Buloz wrote: >> Subject: [PATCH] For exception at PCI probe due to bridge reporting UR >> >> Even if a device supports extended config access, no such access must be >> done to this device If there's a bridge not supporting that in the path >> to this device. Doing such access with UR reporting enabled on the root >> bridge leads to an exception. >> >> This is the case on a LS1043A CPU (NXP QorIQ Layerscape) platform with >> the following bus topology : >> LS1043 PCIe root >> -> PEX8112 PCIe-to-PCI bridge (not supporting ext cfg on PCI side) >> -> PMC slot connector (for legacy PMC modules) >> With a PMC module topology as follows : >> PMC connector >> -> PCI-to-PCIe bridge >> -> PCIe switch (4 ports) >> -> 4 PCIe devices (one on each port) >> In this case all devices behind the PEX8112 are supporting extended config >> access but this is prohibited by the PEX8112. Without this patch, an >> exception (synchronous abort) occurs in pci_cfg_space_size_ext(). >> >> This patch checks the parent bridge of each allocated child bus to know if >> extended config access is supported on the child bus, and sets a flag in >> child->bus_flags if not supported. This flag is inherited by all children >> buses of this child bus and then is checked to avoid this unsupported >> accesses to every device on these buses. > Hi Gilles, > > Thanks for the patch! I reworked it a little bit to simplify the code > in pci_alloc_child_bus(). Can you test it and make sure I didn't > break anything? > Hi Bjorn, Your rework works as expected. Tested on LS1043A platform with kernel 4.17-rc1, and with some backport on kernel 4.1.35 Suggestion : maybe change the pci_info() string to have : pci_bus 0000:xx: extended config space not accessible instead of pci_bus 0000:xx: extended config space not accessible on secondary bus as xx is already the number of the secondary bus Info : with kernel 4.17-rc1, it turns out I need pcie_aspm=off to have the PMC devices behind the PCI-to-PCIe bridge of the PMC safely detected/configured. But this is not caused by the patch. Without pcie_aspm=off I saw this at one boot : "pci 0000:02:0e.0: ASPM: Could not configure common clock" for this bridge, but devices correctly detected/configured but at most boots I get : no ASPM message but "pci 0000:04:02.0: bridge configuration invalid ([bus ff-ff]), reconfiguring " instead, and some devices are missing. Also lspci show "rev ff" for some devices. I don't see this problem on 4.1.35 with the same backported patch. Gilles > commit cbaaa85b558a8f974e301fa0364d568efaf491ce > Author: Gilles Buloz <Gilles.Buloz@kontron.com> > Date: Thu May 3 15:21:44 2018 -0500 > > PCI: Check whether bridges allow access to extended config space > > Even if a device supports extended config space, i.e., it is a PCI-X Mode 2 > or a PCI Express device, the extended space may not be accessible if > there's a conventional PCI bus in the path to it. > > We currently figure that out in pci_cfg_space_size() by reading the first > dword of extended config space. On most platforms that returns ~0 data if > the space is inaccessible, but it may set error bits in PCI status > registers, and on some platforms it causes exceptions that we currently > don't recover from. > > For example, a PCIe-to-conventional PCI bridge treats config transactions > with a non-zero Extended Register Address as an Unsupported Request on PCIe > and a received Master-Abort on the destination bus (see PCI Express to > PCI/PCI-X Bridge spec, r1.0, sec 4.1.3). > > A sample case is a LS1043A CPU (NXP QorIQ Layerscape) platform with the > following bus topology: > > LS1043 PCIe Root Port > -> PEX8112 PCIe-to-PCI bridge (doesn't support ext cfg on PCI side) > -> PMC slot connector (for legacy PMC modules) > > With a PMC module topology as follows: > > PMC connector > -> PCI-to-PCIe bridge > -> PCIe switch (4 ports) > -> 4 PCIe devices (one on each port) > > The PCIe devices on the PMC module support extended config space, but we > can't reach it because the PEX8112 can't generate accesses to the extended > space on its secondary bus. Attempts to access it cause Unsupported > Request errors, which result in synchronous aborts on this platform. > > To avoid these errors, check whether bridges are capable of generating > extended config space addresses on their secondary interfaces. If they > can't, we restrict devices below the bridge to only the 256-byte > PCI-compatible config space. > > Signed-off-by: Gilles Buloz <gilles.buloz@kontron.com> > [bhelgaas: changelog, rework patch so bus_flags testing is all in > pci_bridge_child_ext_cfg_accessible()] > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index ac91b6fd0bcd..7b1b7b2e01e4 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -882,6 +882,45 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) > return err; > } > > +static bool pci_bridge_child_ext_cfg_accessible(struct pci_dev *bridge) > +{ > + int pos; > + u32 status; > + > + /* > + * If extended config space isn't accessible on a bridge's primary > + * bus, we certainly can't access it on the secondary bus. > + */ > + if (bridge->bus->bus_flags & PCI_BUS_FLAGS_NO_EXTCFG) > + return false; > + > + /* > + * PCIe Root Ports and switch ports are PCIe on both sides, so if > + * extended config space is accessible on the primary, it's also > + * accessible on the secondary. > + */ > + if (pci_is_pcie(bridge) && > + (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT || > + pci_pcie_type(bridge) == PCI_EXP_TYPE_UPSTREAM || > + pci_pcie_type(bridge) == PCI_EXP_TYPE_DOWNSTREAM)) > + return true; > + > + /* > + * For the other bridge types: > + * - PCI-to-PCI bridges > + * - PCIe-to-PCI/PCI-X forward bridges > + * - PCI/PCI-X-to-PCIe reverse bridges > + * extended config space on the secondary side is only accessible > + * if the bridge supports PCI-X Mode 2. > + */ > + pos = pci_find_capability(bridge, PCI_CAP_ID_PCIX); > + if (!pos) > + return false; > + > + pci_read_config_dword(bridge, pos + PCI_X_STATUS, &status); > + return status & (PCI_X_STATUS_266MHZ | PCI_X_STATUS_533MHZ); > +} > + > static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent, > struct pci_dev *bridge, int busnr) > { > @@ -923,6 +962,16 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent, > pci_set_bus_of_node(child); > pci_set_bus_speed(child); > > + /* > + * Check whether extended config space is accessible on the child > + * bus. Note that we currently assume it is always accessible on > + * the root bus. > + */ > + if (!pci_bridge_child_ext_cfg_accessible(bridge)) { > + child->bus_flags |= PCI_BUS_FLAGS_NO_EXTCFG; > + pci_info(child, "extended config space not accessible on secondary bus\n"); > + } > + > /* Set up default resource pointers and names */ > for (i = 0; i < PCI_BRIDGE_RESOURCE_NUM; i++) { > child->resource[i] = &bridge->resource[PCI_BRIDGE_RESOURCES+i]; > @@ -1393,6 +1442,9 @@ int pci_cfg_space_size(struct pci_dev *dev) > u32 status; > u16 class; > > + if (dev->bus->bus_flags & PCI_BUS_FLAGS_NO_EXTCFG) > + return PCI_CFG_SPACE_SIZE; > + > class = dev->class >> 8; > if (class == PCI_CLASS_BRIDGE_HOST) > return pci_cfg_space_size_ext(dev); > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 230615620a4a..f7aa6d9f8999 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -217,6 +217,7 @@ enum pci_bus_flags { > PCI_BUS_FLAGS_NO_MSI = (__force pci_bus_flags_t) 1, > PCI_BUS_FLAGS_NO_MMRBC = (__force pci_bus_flags_t) 2, > PCI_BUS_FLAGS_NO_AERSID = (__force pci_bus_flags_t) 4, > + PCI_BUS_FLAGS_NO_EXTCFG = (__force pci_bus_flags_t) 8, > }; > > /* Values from Link Status register, PCIe r3.1, sec 7.8.8 */ > > . >
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index ac91b6fd0bcd..7b1b7b2e01e4 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -882,6 +882,45 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) return err; } +static bool pci_bridge_child_ext_cfg_accessible(struct pci_dev *bridge) +{ + int pos; + u32 status; + + /* + * If extended config space isn't accessible on a bridge's primary + * bus, we certainly can't access it on the secondary bus. + */ + if (bridge->bus->bus_flags & PCI_BUS_FLAGS_NO_EXTCFG) + return false; + + /* + * PCIe Root Ports and switch ports are PCIe on both sides, so if + * extended config space is accessible on the primary, it's also + * accessible on the secondary. + */ + if (pci_is_pcie(bridge) && + (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT || + pci_pcie_type(bridge) == PCI_EXP_TYPE_UPSTREAM || + pci_pcie_type(bridge) == PCI_EXP_TYPE_DOWNSTREAM)) + return true; + + /* + * For the other bridge types: + * - PCI-to-PCI bridges + * - PCIe-to-PCI/PCI-X forward bridges + * - PCI/PCI-X-to-PCIe reverse bridges + * extended config space on the secondary side is only accessible + * if the bridge supports PCI-X Mode 2. + */ + pos = pci_find_capability(bridge, PCI_CAP_ID_PCIX); + if (!pos) + return false; + + pci_read_config_dword(bridge, pos + PCI_X_STATUS, &status); + return status & (PCI_X_STATUS_266MHZ | PCI_X_STATUS_533MHZ); +} + static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent, struct pci_dev *bridge, int busnr) { @@ -923,6 +962,16 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent, pci_set_bus_of_node(child); pci_set_bus_speed(child); + /* + * Check whether extended config space is accessible on the child + * bus. Note that we currently assume it is always accessible on + * the root bus. + */ + if (!pci_bridge_child_ext_cfg_accessible(bridge)) { + child->bus_flags |= PCI_BUS_FLAGS_NO_EXTCFG; + pci_info(child, "extended config space not accessible on secondary bus\n"); + } + /* Set up default resource pointers and names */ for (i = 0; i < PCI_BRIDGE_RESOURCE_NUM; i++) { child->resource[i] = &bridge->resource[PCI_BRIDGE_RESOURCES+i]; @@ -1393,6 +1442,9 @@ int pci_cfg_space_size(struct pci_dev *dev) u32 status; u16 class; + if (dev->bus->bus_flags & PCI_BUS_FLAGS_NO_EXTCFG) + return PCI_CFG_SPACE_SIZE; + class = dev->class >> 8; if (class == PCI_CLASS_BRIDGE_HOST) return pci_cfg_space_size_ext(dev); diff --git a/include/linux/pci.h b/include/linux/pci.h index 230615620a4a..f7aa6d9f8999 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -217,6 +217,7 @@ enum pci_bus_flags { PCI_BUS_FLAGS_NO_MSI = (__force pci_bus_flags_t) 1, PCI_BUS_FLAGS_NO_MMRBC = (__force pci_bus_flags_t) 2, PCI_BUS_FLAGS_NO_AERSID = (__force pci_bus_flags_t) 4, + PCI_BUS_FLAGS_NO_EXTCFG = (__force pci_bus_flags_t) 8, }; /* Values from Link Status register, PCIe r3.1, sec 7.8.8 */