[PATCH RFC] PCI: Turn off BARs when disabling device

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

When unbinding PCI device mlx4 from its driver, the PCI device is
disabled by pci_disable_device() and the BARs (IO and memory) should
be disabled at the point. However, the memory BARs are still active
after the mlx4_core driver is unloaded as following logs show.

 # lspci -vv -s 0003:0f:00.0
 0003:0f:00.0 Network controller: Mellanox Technologies \
              MT27500 Family [ConnectX-3]
 Subsystem: Mellanox Technologies Device 0061
 Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- \
          ParErr+ Stepping- SERR+ FastB2B- DisINTx+
    :
 Kernel driver in use: mlx4_core
 # echo 0003:0f:00.0 > /sys/bus/pci/drivers/mlx4_core/unbind
 # lspci -vv -s 0003:0f:00.0
 0003:0f:00.0 Network controller: Mellanox Technologies \
              MT27500 Family [ConnectX-3]
 Subsystem: Mellanox Technologies Device 0061
 Control: I/O- Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- \
          ParErr+ Stepping- SERR+ FastB2B- DisINTx-

The patch turns off all BARs (IO and memory) in do_pci_disable_device().

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
---
 drivers/pci/pci.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 625a4ac..8d2924b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1496,12 +1496,14 @@ void __weak pcibios_penalize_isa_irq(int irq, int active) {}
 
 static void do_pci_disable_device(struct pci_dev *dev)
 {
-	u16 pci_command;
+	u16 cmd, flags = (PCI_COMMAND_IO |
+			  PCI_COMMAND_MEMORY |
+			  PCI_COMMAND_MASTER);
 
-	pci_read_config_word(dev, PCI_COMMAND, &pci_command);
-	if (pci_command & PCI_COMMAND_MASTER) {
-		pci_command &= ~PCI_COMMAND_MASTER;
-		pci_write_config_word(dev, PCI_COMMAND, pci_command);
+	pci_read_config_word(dev, PCI_COMMAND, &cmd);
+	if (cmd & flags) {
+		cmd &= ~flags;
+		pci_write_config_word(dev, PCI_COMMAND, cmd);
 	}
 
 	pcibios_disable_device(dev);
-- 
1.8.3.2