PCI: Fix regression in pci_restore_state(), v3

Commit 26f41062f2 ("PCI: check for pci bar restore completion and
retry") attempted to address problems with PCI BAR restoration on
systems where FLR had not been completed before pci_restore_state() was
called, but it did that in an utterly wrong way.

First off, instead of retrying the writes for the BAR registers only, it
did that for all of the PCI config space of the device, including the
status register (whose value after the write quite obviously need not be
the same as the written one).  Second, it added arbitrary delay to
pci_restore_state() even for systems where the PCI config space
restoration was successful at first attempt.  Finally, the mdelay(10) it
added to every iteration of the writing loop was way too much of a delay
for any reasonable device.

All of this actually caused resume failures for some devices on Mikko's
system.

To fix the regression, make pci_restore_state() only retry the writes
for BAR registers and only wait if the first read from the register
doesn't return the written value.  Additionaly, make it wait for 1 ms,
instead of 10 ms, after every failing attempt to write into config
space.

Reported-by: Mikko Vinni <mmvinni@yahoo.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/pci/pci.c

@@ -967,16 +967,47 @@ pci_save_state(struct pci_dev *dev)
 	return 0;
 }
 
+static void pci_restore_config_dword(struct pci_dev *pdev, int offset,
+				     u32 saved_val, int retry)
+{
+	u32 val;
+
+	pci_read_config_dword(pdev, offset, &val);
+	if (val == saved_val)
+		return;
+
+	for (;;) {
+		dev_dbg(&pdev->dev, "restoring config space at offset "
+			"%#x (was %#x, writing %#x)\n", offset, val, saved_val);
+		pci_write_config_dword(pdev, offset, saved_val);
+		if (retry-- <= 0)
+			return;
+
+		pci_read_config_dword(pdev, offset, &val);
+		if (val == saved_val)
+			return;
+
+		mdelay(1);
+	}
+}
+
+static void pci_restore_config_space(struct pci_dev *pdev, int start, int end,
+				     int retry)
+{
+	int index;
+
+	for (index = end; index >= start; index--)
+		pci_restore_config_dword(pdev, 4 * index,
+					 pdev->saved_config_space[index],
+					 retry);
+}
+
 /** 
  * pci_restore_state - Restore the saved state of a PCI device
  * @dev: - PCI device that we're dealing with
  */
 void pci_restore_state(struct pci_dev *dev)
 {
-	int i;
-	u32 val;
-	int tries;
-
 	if (!dev->state_saved)
 		return;
 
@@ -984,24 +1015,14 @@ void pci_restore_state(struct pci_dev *dev)
 	pci_restore_pcie_state(dev);
 	pci_restore_ats_state(dev);
 
+	pci_restore_config_space(dev, 10, 15, 0);
 	/*
 	 * The Base Address register should be programmed before the command
 	 * register(s)
 	 */
-	for (i = 15; i >= 0; i--) {
+	pci_restore_config_space(dev, 4, 9, 10);
-		pci_read_config_dword(dev, i * 4, &val);
+	pci_restore_config_space(dev, 0, 3, 0);
-		tries = 10;		
+
-		while (tries && val != dev->saved_config_space[i]) {
-			dev_dbg(&dev->dev, "restoring config "
-				"space at offset %#x (was %#x, writing %#x)\n",
-				i, val, (int)dev->saved_config_space[i]);
-			pci_write_config_dword(dev,i * 4,
-				dev->saved_config_space[i]);
-			pci_read_config_dword(dev, i * 4, &val);
-			mdelay(10);
-			tries--;
-		}
-	}
 	pci_restore_pcix_state(dev);
 	pci_restore_msi_state(dev);
 	pci_restore_iov_state(dev);