PCI: Work around Intel Sunrise Point PCH incorrect ACS capability

Intel Sunrise Point root ports implement ACS but use dwords for the
capability and control registers, putting the control register at the wrong
offset.

Use quirks to enable and test ACS for these devices, which match the
standard functions modulo the broken control register offset.

Note that lspci assumes devices implement ACS per spec, so it shows invalid
ACS data for these devices.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/quirks.c

@@ -3969,6 +3969,55 @@ static int pci_quirk_intel_pch_acs(struct pci_dev *dev, u16 acs_flags)
 	return acs_flags & ~flags ? 0 : 1;
 }
 
+/*
+ * Sunrise Point PCH root ports implement ACS, but unfortunately as shown in
+ * the datasheet (Intel 100 Series Chipset Family PCH Datasheet, Vol. 2,
+ * 12.1.46, 12.1.47)[1] this chipset uses dwords for the ACS capability and
+ * control registers whereas the PCIe spec packs them into words (Rev 3.0,
+ * 7.16 ACS Extended Capability).  The bit definitions are correct, but the
+ * control register is at offset 8 instead of 6 and we should probably use
+ * dword accesses to them.  This applies to the following PCI Device IDs, as
+ * found in volume 1 of the datasheet[2]:
+ *
+ * 0xa110-0xa11f Sunrise Point-H PCI Express Root Port #{0-16}
+ * 0xa167-0xa16a Sunrise Point-H PCI Express Root Port #{17-20}
+ *
+ * N.B. This doesn't fix what lspci shows.
+ *
+ * [1] http://www.intel.com/content/www/us/en/chipsets/100-series-chipset-datasheet-vol-2.html
+ * [2] http://www.intel.com/content/www/us/en/chipsets/100-series-chipset-datasheet-vol-1.html
+ */
+static bool pci_quirk_intel_spt_pch_acs_match(struct pci_dev *dev)
+{
+	return pci_is_pcie(dev) &&
+		pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT &&
+		((dev->device & ~0xf) == 0xa110 ||
+		 (dev->device >= 0xa167 && dev->device <= 0xa16a));
+}
+
+#define INTEL_SPT_ACS_CTRL (PCI_ACS_CAP + 4)
+
+static int pci_quirk_intel_spt_pch_acs(struct pci_dev *dev, u16 acs_flags)
+{
+	int pos;
+	u32 cap, ctrl;
+
+	if (!pci_quirk_intel_spt_pch_acs_match(dev))
+		return -ENOTTY;
+
+	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+	if (!pos)
+		return -ENOTTY;
+
+	/* see pci_acs_flags_enabled() */
+	pci_read_config_dword(dev, pos + PCI_ACS_CAP, &cap);
+	acs_flags &= (cap | PCI_ACS_EC);
+
+	pci_read_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, &ctrl);
+
+	return acs_flags & ~ctrl ? 0 : 1;
+}
+
 static int pci_quirk_mf_endpoint_acs(struct pci_dev *dev, u16 acs_flags)
 {
 	/*
@@ -4057,6 +4106,7 @@ static const struct pci_dev_acs_enabled {
 	{ PCI_VENDOR_ID_INTEL, 0x15b8, pci_quirk_mf_endpoint_acs },
 	/* Intel PCH root ports */
 	{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_quirk_intel_pch_acs },
+	{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_quirk_intel_spt_pch_acs },
 	{ 0x19a2, 0x710, pci_quirk_mf_endpoint_acs }, /* Emulex BE3-R */
 	{ 0x10df, 0x720, pci_quirk_mf_endpoint_acs }, /* Emulex Skyhawk-R */
 	/* Cavium ThunderX */
@@ -4192,12 +4242,40 @@ static int pci_quirk_enable_intel_pch_acs(struct pci_dev *dev)
 	return 0;
 }
 
+static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev)
+{
+	int pos;
+	u32 cap, ctrl;
+
+	if (!pci_quirk_intel_spt_pch_acs_match(dev))
+		return -ENOTTY;
+
+	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+	if (!pos)
+		return -ENOTTY;
+
+	pci_read_config_dword(dev, pos + PCI_ACS_CAP, &cap);
+	pci_read_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, &ctrl);
+
+	ctrl |= (cap & PCI_ACS_SV);
+	ctrl |= (cap & PCI_ACS_RR);
+	ctrl |= (cap & PCI_ACS_CR);
+	ctrl |= (cap & PCI_ACS_UF);
+
+	pci_write_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, ctrl);
+
+	dev_info(&dev->dev, "Intel SPT PCH root port ACS workaround enabled\n");
+
+	return 0;
+}
+
 static const struct pci_dev_enable_acs {
 	u16 vendor;
 	u16 device;
 	int (*enable_acs)(struct pci_dev *dev);
 } pci_dev_enable_acs[] = {
 	{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_quirk_enable_intel_pch_acs },
+	{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_quirk_enable_intel_spt_pch_acs },
 	{ 0 }
 };