Revert "[PATCH] Insert GART region into resource map"

bjorn-helgaas · bjorn-helgaas · commit 707d4eefbdb3 · 2014-03-18T14:26:12.000-06:00
This reverts commit 56dd669, which makes the GART visible in /proc/iomem. This fixes a regression: e501b3d ("agp: Support 64-bit APBASE") exposed an existing problem with a conflict between the GART region and a PCI BAR region. The GART addresses are bus addresses, not CPU addresses, and therefore should not be inserted in iomem_resource. On many machines, the GART region is addressable by the CPU as well as by an AGP master, but CPU addressability is not required by the spec. On some of these machines, the GART is mapped by a PCI BAR, and in that case, the PCI core automatically inserts it into iomem_resource, just as it does for all BARs. Inserting it here means we'll have a conflict if the PCI core later tries to claim the GART region, so let's drop the insertion here. The conflict indirectly causes X failures, as reported by Jouni in the bugzilla below. We detected the conflict even before e501b3d, but after it the AGP code (fix_northbridge()) uses the PCI resource (which is zeroed because of the conflict) instead of reading the BAR again. Conflicts: arch/x86_64/kernel/aperture.c Fixes: e501b3d agp: Support 64-bit APBASE Link: https://bugzilla.kernel.org/show_bug.cgi?id=72201 Reported-and-tested-by: Jouni Mettälä <jtmettala@gmail.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
@@ -18,7 +18,6 @@
 #include <linux/pci_ids.h>
 #include <linux/pci.h>
 #include <linux/bitops.h>
-#include <linux/ioport.h>
 #include <linux/suspend.h>
 #include <asm/e820.h>
 #include <asm/io.h>
@@ -54,18 +53,6 @@ int fallback_aper_force __initdata;
 
 int fix_aperture __initdata = 1;
 
-static struct resource gart_resource = {
-	.name	= "GART",
-	.flags	= IORESOURCE_MEM,
-};
-
-static void __init insert_aperture_resource(u32 aper_base, u32 aper_size)
-{
-	gart_resource.start = aper_base;
-	gart_resource.end = aper_base + aper_size - 1;
-	insert_resource(&iomem_resource, &gart_resource);
-}
-
 /* This code runs before the PCI subsystem is initialized, so just
    access the northbridge directly. */
 
@@ -96,7 +83,6 @@ static u32 __init allocate_aperture(void)
 	memblock_reserve(addr, aper_size);
 	printk(KERN_INFO "Mapping aperture over %d KB of RAM @ %lx\n",
 			aper_size >> 10, addr);
-	insert_aperture_resource((u32)addr, aper_size);
 	register_nosave_region(addr >> PAGE_SHIFT,
 			       (addr+aper_size) >> PAGE_SHIFT);
 
@@ -444,12 +430,8 @@ int __init gart_iommu_hole_init(void)
 
 out:
 	if (!fix && !fallback_aper_force) {
-		if (last_aper_base) {
-			unsigned long n = (32 * 1024 * 1024) << last_aper_order;
-
-			insert_aperture_resource((u32)last_aper_base, n);
+		if (last_aper_base)
 			return 1;
-		}
 		return 0;
 	}
 
