@@ -4928,10 +4928,55 @@ static int pci_dev_reset_slot_function(struct pci_dev *dev, bool probe)
return pci_reset_hotplug_slot(dev->slot->hotplug, probe);
}
+static u16 cxl_port_dvsec(struct pci_dev *dev)
+{
+ return pci_find_dvsec_capability(dev, PCI_VENDOR_ID_CXL,
+ PCI_DVSEC_CXL_PORT);
+}
+
+static bool cxl_sbr_masked(struct pci_dev *dev)
+{
+ u16 dvsec, reg;
+ int rc;
+
+ /*
+ * No DVSEC found, either is not a CXL port, or not connected in which
+ * case mask state is a nop (CXL r3.1 sec 9.12.3 "Enumerating CXL RPs
+ * and DSPs"
+ */
+ dvsec = cxl_port_dvsec(dev);
+ if (!dvsec)
+ return false;
+
+ rc = pci_read_config_word(dev, dvsec + PCI_DVSEC_CXL_PORT_CTL, ®);
+ if (rc || PCI_POSSIBLE_ERROR(reg))
+ return false;
+
+ /*
+ * CXL spec r3.1 8.1.5.2
+ * When 0, SBR bit in Bridge Control register of this Port has no effect.
+ * When 1, the Port shall generate hot reset when SBR bit in Bridge
+ * Control gets set to 1.
+ */
+ if (reg & PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR)
+ return false;
+
+ return true;
+}
+
static int pci_reset_bus_function(struct pci_dev *dev, bool probe)
{
+ struct pci_dev *bridge = pci_upstream_bridge(dev);
int rc;
+ /* If it's a CXL port and the SBR control is masked, fail the SBR */
+ if (bridge && cxl_sbr_masked(bridge)) {
+ if (probe)
+ return 0;
+
+ return -ENOTTY;
+ }
+
rc = pci_dev_reset_slot_function(dev, probe);
if (rc != -ENOTTY)
return rc;
@@ -1148,4 +1148,9 @@
#define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL 0x00ff0000
#define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX 0xff000000
+/* Compute Express Link (CXL) */
+#define PCI_DVSEC_CXL_PORT 3
+#define PCI_DVSEC_CXL_PORT_CTL 0x0c
+#define PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR 0x00000001
+
#endif /* LINUX_PCI_REGS_H */