diff --git a/[refs] b/[refs]
index f98fa9cb5494..41627406b575 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 037a6079eb925f7653bddf1501f777abcd4fc91e
+refs/heads/master: fa3d319ac6f648dc51cb672a31f482c80a8c2457
diff --git a/trunk/arch/x86/kernel/pci-gart_64.c b/trunk/arch/x86/kernel/pci-gart_64.c
index f505c3890358..f20c20a7853d 100644
--- a/trunk/arch/x86/kernel/pci-gart_64.c
+++ b/trunk/arch/x86/kernel/pci-gart_64.c
@@ -824,10 +824,10 @@ void __init gart_iommu_init(void)
 	wbinvd();
 
 	/*
-	 * Try to workaround a bug (thanks to BenH)
+	 * Try to workaround a bug (thanks to BenH):
 	 * Set unmapped entries to a scratch page instead of 0.
 	 * Any prefetches that hit unmapped entries won't get an bus abort
-	 * then.
+	 * then. (P2P bridge may be prefetching on DMA reads).
 	 */
 	scratch = get_zeroed_page(GFP_KERNEL);
 	if (!scratch)