cxl: Workaround malformed pcie packets on some cards

This works around a pcie host bridge defect on some cards, that can cause
malformed Transaction Layer Packet (TLP) errors to be erroneously reported.

The upper nibble of the vendor section PSL revision is used to distinguish
between different cards. The affected ones have it set to 0.
Signed-off-by: Philippe Bergheaud <felix@linux.vnet.ibm.com>
Acked-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/misc/cxl/pci.c

@@ -1035,6 +1035,32 @@ static int cxl_read_vsec(struct cxl *adapter, struct pci_dev *dev)
 	return 0;
 }
 
+/*
+ * Workaround a PCIe Host Bridge defect on some cards, that can cause
+ * malformed Transaction Layer Packet (TLP) errors to be erroneously
+ * reported. Mask this error in the Uncorrectable Error Mask Register.
+ *
+ * The upper nibble of the PSL revision is used to distinguish between
+ * different cards. The affected ones have it set to 0.
+ */
+static void cxl_fixup_malformed_tlp(struct cxl *adapter, struct pci_dev *dev)
+{
+	int aer;
+	u32 data;
+
+	if (adapter->psl_rev & 0xf000)
+		return;
+	if (!(aer = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR)))
+		return;
+	pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, &data);
+	if (data & PCI_ERR_UNC_MALF_TLP)
+		if (data & PCI_ERR_UNC_INTN)
+			return;
+	data |= PCI_ERR_UNC_MALF_TLP;
+	data |= PCI_ERR_UNC_INTN;
+	pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, data);
+}
+
 static int cxl_vsec_looks_ok(struct cxl *adapter, struct pci_dev *dev)
 {
 	if (adapter->vsec_status & CXL_STATUS_SECOND_PORT)
@@ -1134,6 +1160,8 @@ static int cxl_configure_adapter(struct cxl *adapter, struct pci_dev *dev)
 	if ((rc = cxl_vsec_looks_ok(adapter, dev)))
 	        return rc;
 
+	cxl_fixup_malformed_tlp(adapter, dev);
+
 	if ((rc = setup_cxl_bars(dev)))
 		return rc;