From 2f68891314b14e7e0ef07b4e77a8ea6e917fc74b Mon Sep 17 00:00:00 2001
From: Yinghai Lu <yinghai@kernel.org>
Date: Tue, 10 Mar 2009 12:55:50 -0700
Subject: x86/agp: tighten check to update amd nb aperture

Impact: fix bug to make agp work with dri

Jeffrey reported that dri does work with 64bit, but doesn't work with
32bit it turns out NB aperture is 32M, aperture on agp is 128M

64bit is using 64M for vaidation for 64 iommu/gart 32bit is only using
32M..., and will not update the nb aperture.

So try to compare nb apterture and agp apterture before leaving not
touch nb aperture.

Reported-by: Jeffrey Trull <jetrull@sbcglobal.net>
Tested-by: Jeffrey Trull <jetrull@sbcglobal.net>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Dave Airlie <airlied@linux.ie>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/char/agp/amd64-agp.c b/drivers/char/agp/amd64-agp.c
index 52f4361..d765afd 100644
--- a/drivers/char/agp/amd64-agp.c
+++ b/drivers/char/agp/amd64-agp.c
@@ -271,15 +271,15 @@ static __devinit int fix_northbridge(struct pci_dev *nb, struct pci_dev *agp,
 	nb_order = (nb_order >> 1) & 7;
 	pci_read_config_dword(nb, AMD64_GARTAPERTUREBASE, &nb_base);
 	nb_aper = nb_base << 25;
-	if (agp_aperture_valid(nb_aper, (32*1024*1024)<<nb_order)) {
-		return 0;
-	}
 
 	/* Northbridge seems to contain crap. Try the AGP bridge. */
 
 	pci_read_config_word(agp, cap+0x14, &apsize);
-	if (apsize == 0xffff)
+	if (apsize == 0xffff) {
+		if (agp_aperture_valid(nb_aper, (32*1024*1024)<<nb_order))
+			return 0;
 		return -1;
+	}
 
 	apsize &= 0xfff;
 	/* Some BIOS use weird encodings not in the AGPv3 table. */
@@ -301,6 +301,11 @@ static __devinit int fix_northbridge(struct pci_dev *nb, struct pci_dev *agp,
 		order = nb_order;
 	}
 
+	if (nb_order >= order) {
+		if (agp_aperture_valid(nb_aper, (32*1024*1024)<<nb_order))
+			return 0;
+	}
+
 	dev_info(&agp->dev, "aperture from AGP @ %Lx size %u MB\n",
 		 aper, 32 << order);
 	if (order < 0 || !agp_aperture_valid(aper, (32*1024*1024)<<order))
-- 
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