[PATCH v3 06/12] x86/amd_nb: Use topology info to get AMD node count

[Yazen Ghannam <yazen.ghannam@amd.com>]

Currently, the total AMD node count is determined by searching and
counting CPU/node devices using PCI IDs.

However, AMD node information is already available through topology
CPUID/MSRs. The recent topology rework has made this info easier to
access.

Replace the node counting code with a simple product of topology info.

Every node/northbridge is expected to have a 'misc' device. Clear
everything out if a 'misc' device isn't found on a node.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241206161210.163701-8-yazen.ghannam@amd.com
---
 arch/x86/include/asm/amd_node.h |  5 +++++
 arch/x86/kernel/amd_nb.c        | 22 +++++++++++++---------
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/amd_node.h b/arch/x86/include/asm/amd_node.h
index 3f097dd479f8..419a0ad13ef2 100644
--- a/arch/x86/include/asm/amd_node.h
+++ b/arch/x86/include/asm/amd_node.h
@@ -25,4 +25,9 @@
 struct pci_dev *amd_node_get_func(u16 node, u8 func);
 struct pci_dev *amd_node_get_root(u16 node);
 
+static inline u16 amd_num_nodes(void)
+{
+	return topology_amd_nodes_per_pkg() * topology_max_packages();
+}
+
 #endif /*_ASM_X86_AMD_NODE_H_*/
diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index 6218a0428c77..6371fe96b988 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -186,7 +186,6 @@ static int amd_cache_northbridges(void)
 	const struct pci_device_id *misc_ids = amd_nb_misc_ids;
 	struct pci_dev *misc;
 	struct amd_northbridge *nb;
-	u16 misc_count = 0;
 	u16 i;
 
 	if (amd_northbridges.num)
@@ -196,25 +195,30 @@ static int amd_cache_northbridges(void)
 		misc_ids = hygon_nb_misc_ids;
 	}
 
-	misc = NULL;
-	while ((misc = next_northbridge(misc, misc_ids)))
-		misc_count++;
-
-	if (!misc_count)
-		return -ENODEV;
+	amd_northbridges.num = amd_num_nodes();
 
-	nb = kcalloc(misc_count, sizeof(struct amd_northbridge), GFP_KERNEL);
+	nb = kcalloc(amd_northbridges.num, sizeof(struct amd_northbridge), GFP_KERNEL);
 	if (!nb)
 		return -ENOMEM;
 
 	amd_northbridges.nb = nb;
-	amd_northbridges.num = misc_count;
 
 	misc = NULL;
 	for (i = 0; i < amd_northbridges.num; i++) {
 		node_to_amd_nb(i)->root = amd_node_get_root(i);
 		node_to_amd_nb(i)->misc = misc =
 			next_northbridge(misc, misc_ids);
+
+		/*
+		 * Each Northbridge must have a 'misc' device.
+		 * If not, then uninitialize everything.
+		 */
+		if (!node_to_amd_nb(i)->misc) {
+			amd_northbridges.num = 0;
+			kfree(nb);
+			return -ENODEV;
+		}
+
 		node_to_amd_nb(i)->link = amd_node_get_func(i, 4);
 	}
 
-- 
2.43.0