linux-kernel - [PATCH v2 2/4] x86/amd_nb: add support for newer PCI topologies

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Message-ID: <20181106200754.60722-3-brian.woods@amd.com>
Date:   Tue, 6 Nov 2018 20:08:16 +0000
From:   "Woods, Brian" <Brian.Woods@....com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Clemens Ladisch <clemens@...isch.de>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Woods, Brian" <Brian.Woods@....com>, Pu Wen <puwen@...on.cn>,
        Jia Zhang <qianyue.zj@...baba-inc.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: [PATCH v2 2/4] 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@....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