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authorJames Puthukattukaran <james.puthukattukaran@oracle.com>2018-07-09 18:31:25 +0300
committerBjorn Helgaas <helgaas@kernel.org>2018-07-13 00:54:35 +0300
commitaa667c6408d20a84c7637420bc3b7aa0abab59a2 (patch)
treed009885df95a599732f81416174e515ac9a7dfb4 /drivers/pci/probe.c
parentce397d215ccd07b8ae3f71db689aedb85d56ab40 (diff)
downloadlinux-aa667c6408d20a84c7637420bc3b7aa0abab59a2.tar.xz
PCI: Workaround IDT switch ACS Source Validation erratum
Some IDT switches incorrectly flag an ACS Source Validation error on completions for config read requests even though PCIe r4.0, sec 6.12.1.1, says that completions are never affected by ACS Source Validation. Here's the text of IDT 89H32H8G3-YC, erratum #36: Item #36 - Downstream port applies ACS Source Validation to Completions Section 6.12.1.1 of the PCI Express Base Specification 3.1 states that completions are never affected by ACS Source Validation. However, completions received by a downstream port of the PCIe switch from a device that has not yet captured a PCIe bus number are incorrectly dropped by ACS Source Validation by the switch downstream port. Workaround: Issue a CfgWr1 to the downstream device before issuing the first CfgRd1 to the device. This allows the downstream device to capture its bus number; ACS Source Validation no longer stops completions from being forwarded by the downstream port. It has been observed that Microsoft Windows implements this workaround already; however, some versions of Linux and other operating systems may not. When doing the first config read to probe for a device, if the device is behind an IDT switch with this erratum: 1. Disable ACS Source Validation if enabled 2. Wait for device to become ready to accept config accesses (by using the Config Request Retry Status mechanism) 3. Do a config write to the endpoint 4. Enable ACS Source Validation (if it was enabled to begin with) The workaround suggested by IDT is basically only step 3, but we don't know when the device is ready to accept config requests. That means we need to do config reads until we receive a non-Config Request Retry Status, which means we need to disable ACS SV temporarily. Signed-off-by: James Puthukattukaran <james.puthukattukaran@oracle.com> [bhelgaas: changelog, clean up whitespace, fold in unused variable fix from Anders Roxell <anders.roxell@linaro.org>] Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Diffstat (limited to 'drivers/pci/probe.c')
-rw-r--r--drivers/pci/probe.c22
1 files changed, 20 insertions, 2 deletions
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ac876e32de4b..7c0c8ab94bcf 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2156,8 +2156,8 @@ static bool pci_bus_wait_crs(struct pci_bus *bus, int devfn, u32 *l,
return true;
}
-bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *l,
- int timeout)
+bool pci_bus_generic_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *l,
+ int timeout)
{
if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, l))
return false;
@@ -2172,6 +2172,24 @@ bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *l,
return true;
}
+
+bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *l,
+ int timeout)
+{
+#ifdef CONFIG_PCI_QUIRKS
+ struct pci_dev *bridge = bus->self;
+
+ /*
+ * Certain IDT switches have an issue where they improperly trigger
+ * ACS Source Validation errors on completions for config reads.
+ */
+ if (bridge && bridge->vendor == PCI_VENDOR_ID_IDT &&
+ bridge->device == 0x80b5)
+ return pci_idt_bus_quirk(bus, devfn, l, timeout);
+#endif
+
+ return pci_bus_generic_read_dev_vendor_id(bus, devfn, l, timeout);
+}
EXPORT_SYMBOL(pci_bus_read_dev_vendor_id);
/*