Improve PCI config space writeback.

Dave Jones
2006-04-16T22:42:16Z

At least one laptop blew up on resume from suspend with a black screen
due to a lack of this patch. By only writing back config space that
is different, we minimise the possibility of accidents like this.

Signed-off-by: Dave Jones <davej@redhat.com>

--- linux-2.6.16.noarch/drivers/pci/pci.c~ 2006-04-16 17:36:34.000000000 -0500
+++ linux-2.6.16.noarch/drivers/pci/pci.c 2006-04-16 17:37:42.000000000 -0500
@@ -461,9 +461,17 @@ int
pci_restore_state(struct pci_dev *dev)
{
int i;
+ int val;

- for (i = 0; i < 16; i++)
- pci_write_config_dword(dev,i * 4, dev->saved_config_space[i]);
+ for (i = 0; i < 16; i++) {
+ pci_read_config_dword(dev, i * 4, &val);
+ if (val != dev->saved_config_space[i]) {
+ printk (KERN_DEBUG "PM: Writing back config space on device %s at offset %x. (Was %x, writing %x)\n",
+ pci_name(dev), i,
+ val, (int) dev->saved_config_space[i]);
+ pci_write_config_dword(dev,i * 4, dev->saved_config_space[i]);
+ }
+ }
pci_restore_msi_state(dev);
pci_restore_msix_state(dev);
return 0;