From: Dave Jones <davej@redhat.com>
Date: Wed, 19 Apr 2006 04:06:51 +0000 (-0700)
Subject: [PATCH] PCI: Improve PCI config space writeback
X-Git-Tag: v2.6.17~25^2~1
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=04d9c1a1100b6bdeffa7e1bfc30080bdac28e183;p=karo-tx-linux.git

[PATCH] PCI: Improve PCI config space writeback

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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 2329f941a0dc..d2520451f36b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -461,9 +461,19 @@ int
 pci_restore_state(struct pci_dev *dev)
 {
 	int i;
-
-	for (i = 0; i < 16; i++)
-		pci_write_config_dword(dev,i * 4, dev->saved_config_space[i]);
+	int val;
+
+	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;