x86, k8 nb: Fix boot crash: enable k8_northbridges unconditionally on AMD systems

de957628ce7c84764ff41331111036b3ae5bad0f changed setting of the
x86_init.iommu.iommu_init function ptr only when GART IOMMU is
found.

One side effect of it is that num_k8_northbridges
is not initialized anymore if not explicitly
called. This resulted in uninitialized pointers in
<arch/x86/kernel/cpu/intel_cacheinfo.c:amd_calc_l3_indices()>,
for example, which uses the num_k8_northbridges thing through
node_to_k8_nb_misc().

Fix that through an initcall that runs right after the PCI
subsystem and does all the scanning. Then, remove initialization
in gart_iommu_init() which is a rootfs_initcall and we're
running before that.

What is more, since num_k8_northbridges is being used in other
places beside GART IOMMU, include it whenever we add AMD CPU
support. The previous dependency chain in kconfig contained

K8_NB depends on AGP_AMD64|GART_IOMMU

which was clearly incorrect. The more natural way in terms of
hardware dependency should be

AGP_AMD64|GART_IOMMU depends on K8_NB depends on CPU_SUP_AMD &&
PCI. Make it so Number One!

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Joerg Roedel <joerg.roedel@amd.com>
LKML-Reference: <20100312144303.GA29262@aftab>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Tested-by: Joerg Roedel <joerg.roedel@amd.com>

arch/x86/Kconfig

@@ -627,7 +627,7 @@ config GART_IOMMU
 	bool "GART IOMMU support" if EMBEDDED
 	default y
 	select SWIOTLB
-	depends on X86_64 && PCI
+	depends on X86_64 && PCI && K8_NB
 	---help---
 	  Support for full DMA access of devices with 32bit memory access only
 	  on systems with more than 3GB. This is usually needed for USB,
@@ -2026,7 +2026,7 @@ endif # X86_32
 
 config K8_NB
 	def_bool y
-	depends on AGP_AMD64 || (X86_64 && (GART_IOMMU || (PCI && NUMA)))
+	depends on CPU_SUP_AMD && PCI
 
 source "drivers/pcmcia/Kconfig"
 

arch/x86/kernel/k8.c

@@ -121,3 +121,17 @@ void k8_flush_garts(void)
 }
 EXPORT_SYMBOL_GPL(k8_flush_garts);
 
+static __init int init_k8_nbs(void)
+{
+	int err = 0;
+
+	err = cache_k8_northbridges();
+
+	if (err < 0)
+		printk(KERN_NOTICE "K8 NB: Cannot enumerate AMD northbridges.\n");
+
+	return err;
+}
+
+/* This has to go after the PCI subsystem */
+fs_initcall(init_k8_nbs);

arch/x86/kernel/pci-gart_64.c

@@ -735,7 +735,7 @@ int __init gart_iommu_init(void)
 	unsigned long scratch;
 	long i;
 
-	if (cache_k8_northbridges() < 0 || num_k8_northbridges == 0)
+	if (num_k8_northbridges == 0)
 		return 0;
 
 #ifndef CONFIG_AGP_AMD64

drivers/char/agp/Kconfig

@@ -57,7 +57,7 @@ config AGP_AMD
 
 config AGP_AMD64
 	tristate "AMD Opteron/Athlon64 on-CPU GART support"
-	depends on AGP && X86
+	depends on AGP && X86 && K8_NB
 	help
 	  This option gives you AGP support for the GLX component of
 	  X using the on-CPU northbridge of the AMD Athlon64/Opteron CPUs.