Re: Improve PCI config space writeback.

Benjamin Herrenschmidt
2006-04-17T00:27:21Z

On Sun, 2006-04-16 at 17:42 -0500, Dave Jones wrote:
> 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>

I think it's a mistake to restore the command register before the rest.
It should be restored last.

>
> --- 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;
> -
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