cxl/pci: Introduce cxl_gpf_get_dvsec()

Add a helper to fetch the port/device GPF dvsecs. This is
currently only used for ports, but a later patch to export
dirty count to users will make use of the device one.

Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Li Ming <ming.li@zohomail.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://patch.msgid.link/20250220220235.276831-2-dave@stgolabs.net
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Author: Davidlohr Bueso

drivers/cxl/core/pci.c

@@ -1072,6 +1072,22 @@ int cxl_pci_get_bandwidth(struct pci_dev *pdev, struct access_coordinate *c)
 #define GPF_TIMEOUT_BASE_MAX 2
 #define GPF_TIMEOUT_SCALE_MAX 7 /* 10 seconds */
 
+u16 cxl_gpf_get_dvsec(struct device *dev, bool is_port)
+{
+	u16 dvsec;
+
+	if (!dev_is_pci(dev))
+		return 0;
+
+	dvsec = pci_find_dvsec_capability(to_pci_dev(dev), PCI_VENDOR_ID_CXL,
+			is_port ? CXL_DVSEC_PORT_GPF : CXL_DVSEC_DEVICE_GPF);
+	if (!dvsec)
+		dev_warn(dev, "%s GPF DVSEC not present\n",
+			 is_port ? "Port" : "Device");
+	return dvsec;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_gpf_get_dvsec, "CXL");
+
 static int update_gpf_port_dvsec(struct pci_dev *pdev, int dvsec, int phase)
 {
 	u64 base, scale;
@@ -1116,26 +1132,20 @@ int cxl_gpf_port_setup(struct device *dport_dev, struct cxl_port *port)
 {
 	struct pci_dev *pdev;
 
-	if (!dev_is_pci(dport_dev))
-		return 0;
-
-	pdev = to_pci_dev(dport_dev);
-	if (!pdev || !port)
+	if (!port)
 		return -EINVAL;
 
 	if (!port->gpf_dvsec) {
 		int dvsec;
 
-		dvsec = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL,
-						  CXL_DVSEC_PORT_GPF);
-		if (!dvsec) {
-			pci_warn(pdev, "Port GPF DVSEC not present\n");
+		dvsec = cxl_gpf_get_dvsec(dport_dev, true);
+		if (!dvsec)
 			return -EINVAL;
-		}
 
 		port->gpf_dvsec = dvsec;
 	}
 
+	pdev = to_pci_dev(dport_dev);
 	update_gpf_port_dvsec(pdev, port->gpf_dvsec, 1);
 	update_gpf_port_dvsec(pdev, port->gpf_dvsec, 2);
 

drivers/cxl/cxl.h

@@ -922,4 +922,6 @@ bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port);
 #define __mock static
 #endif
 
+u16 cxl_gpf_get_dvsec(struct device *dev, bool is_port);
+
 #endif /* __CXL_H__ */