pcie: utilize pcie transaction pending bit

PCIE has a mechanism to wait for Non-Posted request to complete. I think
pci_disable_device is a good place to do this.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/pci/pci.c

@@ -314,6 +314,24 @@ int pci_find_ht_capability(struct pci_dev *dev, int ht_cap)
 }
 EXPORT_SYMBOL_GPL(pci_find_ht_capability);
 
+void pcie_wait_pending_transaction(struct pci_dev *dev)
+{
+	int pos;
+	u16 reg16;
+
+	pos = pci_find_capability(dev, PCI_CAP_ID_EXP);
+	if (!pos)
+		return;
+	while (1) {
+		pci_read_config_word(dev, pos + PCI_EXP_DEVSTA, &reg16);
+		if (!(reg16 & PCI_EXP_DEVSTA_TRPND))
+			break;
+		cpu_relax();
+	}
+
+}
+EXPORT_SYMBOL_GPL(pcie_wait_pending_transaction);
+
 /**
  * pci_find_parent_resource - return resource region of parent bus of given region
  * @dev: PCI device structure contains resources to be searched
@@ -884,6 +902,9 @@ pci_disable_device(struct pci_dev *dev)
 	if (atomic_sub_return(1, &dev->enable_cnt) != 0)
 		return;
 
+	/* Wait for all transactions are finished before disabling the device */
+	pcie_wait_pending_transaction(dev);
+
 	pci_read_config_word(dev, PCI_COMMAND, &pci_command);
 	if (pci_command & PCI_COMMAND_MASTER) {
 		pci_command &= ~PCI_COMMAND_MASTER;

include/linux/pci.h

@@ -498,6 +498,7 @@ int pci_find_next_capability (struct pci_dev *dev, u8 pos, int cap);
 int pci_find_ext_capability (struct pci_dev *dev, int cap);
 int pci_find_ht_capability (struct pci_dev *dev, int ht_cap);
 int pci_find_next_ht_capability (struct pci_dev *dev, int pos, int ht_cap);
+void pcie_wait_pending_transaction(struct pci_dev *dev);
 struct pci_bus *pci_find_next_bus(const struct pci_bus *from);
 
 struct pci_dev *pci_get_device(unsigned int vendor, unsigned int device,
@@ -759,6 +760,7 @@ static inline void pci_unregister_driver(struct pci_driver *drv) { }
 static inline int pci_find_capability (struct pci_dev *dev, int cap) {return 0; }
 static inline int pci_find_next_capability (struct pci_dev *dev, u8 post, int cap) { return 0; }
 static inline int pci_find_ext_capability (struct pci_dev *dev, int cap) {return 0; }
+static inline void pcie_wait_pending_transaction(struct pci_dev *dev) {}
 
 /* Power management related routines */
 static inline int pci_save_state(struct pci_dev *dev) { return 0; }