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authorNathan Rossi <nathan.rossi@digi.com>2021-09-10 02:58:23 +0000
committerBjorn Helgaas <bhelgaas@google.com>2021-11-05 06:07:44 -0500
commitacd61ffb2f1678fa5eb4170a3a4c530145fe2e64 (patch)
tree595dddc5a87ad5e6e771d17eb0616c5f42e22fd0 /drivers/pci/quirks.c
parente3f4bd3462f6f796594ecc0dda7144ed2d1e5a26 (diff)
PCI: Add ACS quirk for Pericom PI7C9X2G switches
The Pericom PI7C9X2G404/PI7C9X2G304/PI7C9X2G303 PCIe switches have an erratum for ACS P2P Request Redirect behaviour when used in the cut-through forwarding mode. The recommended work around for this issue is to use the switch in store and forward mode. The erratum results in packets being queued and not being delivered upstream, which can be observed as very poor downstream device performance and/or dropped device-generated data/interrupts. Add a fixup so that when enabling or resuming the downstream port we check if it has enabled ACS P2P Request Redirect, and if so, change the device (via the upstream port) to use the store and forward operating mode. Link: https://bugzilla.kernel.org/show_bug.cgi?id=177471 Link: https://lore.kernel.org/r/20210910025823.196508-1-nathan@nathanrossi.com Tested-by: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Nathan Rossi <nathan.rossi@digi.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'drivers/pci/quirks.c')
-rw-r--r--drivers/pci/quirks.c55
1 files changed, 55 insertions, 0 deletions
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 6c957124f84d..126c256bbb8a 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -5796,3 +5796,58 @@ static void apex_pci_fixup_class(struct pci_dev *pdev)
}
DECLARE_PCI_FIXUP_CLASS_HEADER(0x1ac1, 0x089a,
PCI_CLASS_NOT_DEFINED, 8, apex_pci_fixup_class);
+
+/*
+ * Pericom PI7C9X2G404/PI7C9X2G304/PI7C9X2G303 switch erratum E5 -
+ * ACS P2P Request Redirect is not functional
+ *
+ * When ACS P2P Request Redirect is enabled and bandwidth is not balanced
+ * between upstream and downstream ports, packets are queued in an internal
+ * buffer until CPLD packet. The workaround is to use the switch in store and
+ * forward mode.
+ */
+#define PI7C9X2Gxxx_MODE_REG 0x74
+#define PI7C9X2Gxxx_STORE_FORWARD_MODE BIT(0)
+static void pci_fixup_pericom_acs_store_forward(struct pci_dev *pdev)
+{
+ struct pci_dev *upstream;
+ u16 val;
+
+ /* Downstream ports only */
+ if (pci_pcie_type(pdev) != PCI_EXP_TYPE_DOWNSTREAM)
+ return;
+
+ /* Check for ACS P2P Request Redirect use */
+ if (!pdev->acs_cap)
+ return;
+ pci_read_config_word(pdev, pdev->acs_cap + PCI_ACS_CTRL, &val);
+ if (!(val & PCI_ACS_RR))
+ return;
+
+ upstream = pci_upstream_bridge(pdev);
+ if (!upstream)
+ return;
+
+ pci_read_config_word(upstream, PI7C9X2Gxxx_MODE_REG, &val);
+ if (!(val & PI7C9X2Gxxx_STORE_FORWARD_MODE)) {
+ pci_info(upstream, "Setting PI7C9X2Gxxx store-forward mode to avoid ACS erratum\n");
+ pci_write_config_word(upstream, PI7C9X2Gxxx_MODE_REG, val |
+ PI7C9X2Gxxx_STORE_FORWARD_MODE);
+ }
+}
+/*
+ * Apply fixup on enable and on resume, in order to apply the fix up whenever
+ * ACS configuration changes or switch mode is reset
+ */
+DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_PERICOM, 0x2404,
+ pci_fixup_pericom_acs_store_forward);
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_PERICOM, 0x2404,
+ pci_fixup_pericom_acs_store_forward);
+DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_PERICOM, 0x2304,
+ pci_fixup_pericom_acs_store_forward);
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_PERICOM, 0x2304,
+ pci_fixup_pericom_acs_store_forward);
+DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_PERICOM, 0x2303,
+ pci_fixup_pericom_acs_store_forward);
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_PERICOM, 0x2303,
+ pci_fixup_pericom_acs_store_forward);