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Subject[PATCH v2 2/4] x86/amd_nb: add support for newer PCI topologies
Date
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>
---
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 19d489ee2b1e..cc34266e3c62 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -213,7 +213,10 @@ int amd_cache_northbridges(void)
const struct pci_device_id *root_ids = amd_root_ids;
struct pci_dev *root, *misc, *link;
struct amd_northbridge *nb;
- u16 i = 0;
+ u16 roots_per_misc = 0;
+ u16 misc_count = 0;
+ u16 root_count = 0;
+ u16 i, j;

if (amd_northbridges.num)
return 0;
@@ -226,26 +229,55 @@ int amd_cache_northbridges(void)

misc = NULL;
while ((misc = next_northbridge(misc, 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, root_ids);
node_to_amd_nb(i)->misc = misc =
next_northbridge(misc, misc_ids);
node_to_amd_nb(i)->link = link =
next_northbridge(link, 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())
--
2.11.0
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