PCI: Add array to track reset method ordering

Add reset_methods[] in struct pci_dev to keep track of reset mechanisms
supported by the device and their ordering.

Refactor probing and reset functions to take advantage of calling
convention of reset functions.

Co-developed-by: Alex Williamson <alex.williamson@redhat.com>
Link: https://lore.kernel.org/r/20210817180500.1253-4-ameynarkhede03@gmail.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Amey Narkhede <ameynarkhede03@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>

drivers/pci/pci.c

@@ -73,6 +73,11 @@ static void pci_dev_d3_sleep(struct pci_dev *dev)
 		msleep(delay);
 }
 
+bool pci_reset_supported(struct pci_dev *dev)
+{
+	return dev->reset_methods[0] != 0;
+}
+
 #ifdef CONFIG_PCI_DOMAINS
 int pci_domains_supported = 1;
 #endif
@@ -5117,6 +5122,16 @@ static void pci_dev_restore(struct pci_dev *dev)
 		err_handler->reset_done(dev);
 }
 
+/* dev->reset_methods[] is a 0-terminated list of indices into this array */
+static const struct pci_reset_fn_method pci_reset_fn_methods[] = {
+	{ },
+	{ pci_dev_specific_reset, .name = "device_specific" },
+	{ pcie_reset_flr, .name = "flr" },
+	{ pci_af_flr, .name = "af_flr" },
+	{ pci_pm_reset, .name = "pm" },
+	{ pci_reset_bus_function, .name = "bus" },
+};
+
 /**
  * __pci_reset_function_locked - reset a PCI device function while holding
  * the @dev mutex lock.
@@ -5139,65 +5154,64 @@ static void pci_dev_restore(struct pci_dev *dev)
  */
 int __pci_reset_function_locked(struct pci_dev *dev)
 {
-	int rc;
+	int i, m, rc = -ENOTTY;
 
 	might_sleep();
 
 	/*
-	 * A reset method returns -ENOTTY if it doesn't support this device
+	 * A reset method returns -ENOTTY if it doesn't support this device and
-	 * and we should try the next method.
+	 * we should try the next method.
 	 *
-	 * If it returns 0 (success), we're finished.  If it returns any
+	 * If it returns 0 (success), we're finished.  If it returns any other
-	 * other error, we're also finished: this indicates that further
+	 * error, we're also finished: this indicates that further reset
-	 * reset mechanisms might be broken on the device.
+	 * mechanisms might be broken on the device.
 	 */
-	rc = pci_dev_specific_reset(dev, 0);
+	for (i = 0; i < PCI_NUM_RESET_METHODS; i++) {
+		m = dev->reset_methods[i];
+		if (!m)
+			return -ENOTTY;
+
+		rc = pci_reset_fn_methods[m].reset_fn(dev, 0);
+		if (!rc)
+			return 0;
 		if (rc != -ENOTTY)
 			return rc;
-	rc = pcie_reset_flr(dev, 0);
+	}
-	if (rc != -ENOTTY)
+
-		return rc;
+	return -ENOTTY;
-	rc = pci_af_flr(dev, 0);
-	if (rc != -ENOTTY)
-		return rc;
-	rc = pci_pm_reset(dev, 0);
-	if (rc != -ENOTTY)
-		return rc;
-	return pci_reset_bus_function(dev, 0);
 }
 EXPORT_SYMBOL_GPL(__pci_reset_function_locked);
 
 /**
- * pci_probe_reset_function - check whether the device can be safely reset
+ * pci_init_reset_methods - check whether device can be safely reset
- * @dev: PCI device to reset
+ * and store supported reset mechanisms.
+ * @dev: PCI device to check for reset mechanisms
  *
  * Some devices allow an individual function to be reset without affecting
- * other functions in the same device.  The PCI device must be responsive
+ * other functions in the same device.  The PCI device must be in D0-D3hot
- * to PCI config space in order to use this function.
+ * state.
  *
- * Returns 0 if the device function can be reset or negative if the
+ * Stores reset mechanisms supported by device in reset_methods byte array
- * device doesn't support resetting a single function.
+ * which is a member of struct pci_dev.
  */
-int pci_probe_reset_function(struct pci_dev *dev)
+void pci_init_reset_methods(struct pci_dev *dev)
 {
-	int rc;
+	int m, i, rc;
+
+	BUILD_BUG_ON(ARRAY_SIZE(pci_reset_fn_methods) != PCI_NUM_RESET_METHODS);
 
 	might_sleep();
 
-	rc = pci_dev_specific_reset(dev, 1);
+	i = 0;
-	if (rc != -ENOTTY)
+	for (m = 1; m < PCI_NUM_RESET_METHODS; m++) {
-		return rc;
+		rc = pci_reset_fn_methods[m].reset_fn(dev, 1);
-	rc = pcie_reset_flr(dev, 1);
+		if (!rc)
-	if (rc != -ENOTTY)
+			dev->reset_methods[i++] = m;
-		return rc;
+		else if (rc != -ENOTTY)
-	rc = pci_af_flr(dev, 1);
+			break;
-	if (rc != -ENOTTY)
+	}
-		return rc;
-	rc = pci_pm_reset(dev, 1);
-	if (rc != -ENOTTY)
-		return rc;
 
-	return pci_reset_bus_function(dev, 1);
+	dev->reset_methods[i] = 0;
 }
 
 /**

drivers/pci/pci.h

@@ -33,7 +33,8 @@ enum pci_mmap_api {
 int pci_mmap_fits(struct pci_dev *pdev, int resno, struct vm_area_struct *vmai,
 		  enum pci_mmap_api mmap_api);
 
-int pci_probe_reset_function(struct pci_dev *dev);
+bool pci_reset_supported(struct pci_dev *dev);
+void pci_init_reset_methods(struct pci_dev *dev);
 int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
 int pci_bus_error_reset(struct pci_dev *dev);
 
@@ -610,6 +611,11 @@ struct pci_dev_reset_methods {
 	int (*reset)(struct pci_dev *dev, int probe);
 };
 
+struct pci_reset_fn_method {
+	int (*reset_fn)(struct pci_dev *pdev, int probe);
+	char *name;
+};
+
 #ifdef CONFIG_PCI_QUIRKS
 int pci_dev_specific_reset(struct pci_dev *dev, int probe);
 #else

drivers/pci/probe.c

@@ -2429,9 +2429,8 @@ static void pci_init_capabilities(struct pci_dev *dev)
 	pci_rcec_init(dev);		/* Root Complex Event Collector */
 
 	pcie_report_downtraining(dev);
-
+	pci_init_reset_methods(dev);
-	if (pci_probe_reset_function(dev) == 0)
+	dev->reset_fn = pci_reset_supported(dev);
-		dev->reset_fn = 1;
 }
 
 /*

include/linux/pci.h

@@ -49,6 +49,9 @@
 			       PCI_STATUS_SIG_TARGET_ABORT | \
 			       PCI_STATUS_PARITY)
 
+/* Number of reset methods used in pci_reset_fn_methods array in pci.c */
+#define PCI_NUM_RESET_METHODS 6
+
 /*
  * The PCI interface treats multi-function devices as independent
  * devices.  The slot/function address of each device is encoded
@@ -506,6 +509,9 @@ struct pci_dev {
 	char		*driver_override; /* Driver name to force a match */
 
 	unsigned long	priv_flags;	/* Private flags for the PCI driver */
+
+	/* These methods index pci_reset_fn_methods[] */
+	u8 reset_methods[PCI_NUM_RESET_METHODS]; /* In priority order */
 };
 
 static inline struct pci_dev *pci_physfn(struct pci_dev *dev)