x86/amd_nb: Add support for newer PCI topologies

BugLink: https://bugs.launchpad.net/bugs/1819485
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@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
CC: Bjorn Helgaas <bhelgaas@google.com>
CC: Clemens Ladisch <clemens@ladisch.de>
CC: Guenter Roeck <linux@roeck-us.net>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Ingo Molnar <mingo@redhat.com>
CC: Jean Delvare <jdelvare@suse.com>
CC: Jia Zhang <qianyue.zj@alibaba-inc.com>
CC: <linux-hwmon@vger.kernel.org>
CC: <linux-pci@vger.kernel.org>
CC: Pu Wen <puwen@hygon.cn>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: x86-ml <x86@kernel.org>
Link: http://lkml.kernel.org/r/20181106200754.60722-3-brian.woods@amd.com
(backported from commit 556e4c62baffa71e2045a298379db7e57dd47f3d)
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Acked-by: Khalid Elmously <khalid.elmously@canonical.com>
Acked-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index b95db8ce83bf71bac38fc8c8e1623c95cb9224e4..72a5555c1077bbad63d7c8392b6ccc5fdd6b1c88 100644 (file)
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -199,35 +199,67 @@ EXPORT_SYMBOL_GPL(amd_df_indirect_read);
 
 int amd_cache_northbridges(void)
 {
-       u16 i = 0;
+       const struct pci_device_id *root_ids = amd_root_ids;
        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())