[Bionic][PATCH 2/5] x86/amd_nb: Add support for newer PCI topologies

[Naru, Kim]

BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1819485

    x86/amd_nb: Add support for newer PCI topologies

    Add support for new processors which have multiple PCI root complexes
    per data fabric/system management network interface.  If there are (N)
    multiple PCI roots per DF/SMN interface, then the PCI roots are
    redundant (as far as SMN/DF access goes).  For each DF/SMN interface:
    map to the first available PCI root and skip the next N-1 PCI roots so
    the following DF/SMN interface get mapped to a correct PCI root.

    Ex:
    DF/SMN 0 -> 60
                40
                20
                00
    DF/SMN 1 -> e0
                c0
                a0
                80

    Signed-off-by: Brian Woods <brian.woods at amd.com>
    (backported from commit 556e4c62baffa71e2045a298379db7e57dd47f3d)
    Signed-off-by: Borislav Petkov <bp at suse.de>
    CC: Bjorn Helgaas <bhelgaas at google.com>
    CC: Clemens Ladisch <clemens at ladisch.de>
    CC: Guenter Roeck <linux at roeck-us.net>
    CC: "H. Peter Anvin" <hpa at zytor.com>
    CC: Ingo Molnar <mingo at redhat.com>
    CC: Jean Delvare <jdelvare at suse.com>
    CC: Jia Zhang <qianyue.zj at alibaba-inc.com>
    CC: <linux-hwmon at vger.kernel.org>
    CC: <linux-pci at vger.kernel.org>
    CC: Pu Wen <puwen at hygon.cn>
    CC: Thomas Gleixner <tglx at linutronix.de>
    CC: x86-ml <x86 at kernel.org>
    Link: http://lkml.kernel.org/r/20181106200754.60722-3-brian.woods@amd.com
---
 arch/x86/kernel/amd_nb.c | 44 ++++++++++++++++++++++++++++++++++------
 1 file changed, 38 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index bf440af5ff9c..88ba353158e4 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -193,35 +193,67 @@ EXPORT_SYMBOL_GPL(amd_df_indirect_read);
 
 int amd_cache_northbridges(void)
 {
-	u16 i = 0;
 	struct amd_northbridge *nb;
 	struct pci_dev *root, *misc, *link;
+	u16 roots_per_misc = 0;
+	u16 misc_count = 0;
+	u16 root_count = 0;
+	u16 i, j;
 
 	if (amd_northbridges.num)
 		return 0;
 
 	misc = NULL;
 	while ((misc = next_northbridge(misc, amd_nb_misc_ids)) != NULL)
-		i++;
+		misc_count++;
 
-	if (!i)
+	if (!misc_count)
 		return -ENODEV;
 
-	nb = kcalloc(i, sizeof(struct amd_northbridge), GFP_KERNEL);
+	root = NULL;
+	while ((root = next_northbridge(root, root_ids)) != NULL)
+		root_count++;
+
+	if (root_count) {
+		roots_per_misc = root_count / misc_count;
+
+		/*
+		 * There should be _exactly_ N roots for each DF/SMN
+		 * interface.
+		 */
+		if (!roots_per_misc || (root_count % roots_per_misc)) {
+			pr_info("Unsupported AMD DF/PCI configuration found\n");
+			return -ENODEV;
+		}
+	}
+
+	nb = kcalloc(misc_count, sizeof(struct amd_northbridge), GFP_KERNEL);
 	if (!nb)
 		return -ENOMEM;
 
 	amd_northbridges.nb = nb;
-	amd_northbridges.num = i;
+	amd_northbridges.num = misc_count;
 
 	link = misc = root = NULL;
-	for (i = 0; i != amd_northbridges.num; i++) {
+	for (i = 0; i < amd_northbridges.num; i++) {
 		node_to_amd_nb(i)->root = root =
 			next_northbridge(root, amd_root_ids);
 		node_to_amd_nb(i)->misc = misc =
 			next_northbridge(misc, amd_nb_misc_ids);
 		node_to_amd_nb(i)->link = link =
 			next_northbridge(link, amd_nb_link_ids);
+
+		/*
+		 * If there are more PCI root devices than data fabric/
+		 * system management network interfaces, then the (N)
+		 * PCI roots per DF/SMN interface are functionally the
+		 * same (for DF/SMN access) and N-1 are redundant.  N-1
+		 * PCI roots should be skipped per DF/SMN interface so
+		 * the following DF/SMN interfaces get mapped to
+		 * correct PCI roots.
+		 */
+		for (j = 1; j < roots_per_misc; j++)
+			root = next_northbridge(root, root_ids);
 	}
 
 	if (amd_gart_present())
-- 
2.21.0