[RFC PATCH v2 24/28] cxl/region: HB port config verification

[Ben Widawsky <ben.widawsky@intel.com>]

Host bridge root port verification determines if the device ordering in
an interleave set can be programmed through the host bridges and
switches.

The algorithm implemented here is based on the CXL Type 3 Memory Device
Software Guide, chapter 2.13.15

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
 .clang-format        |  1 +
 drivers/cxl/cxl.h    |  3 ++
 drivers/cxl/region.c | 90 +++++++++++++++++++++++++++++++++++++++++++-
 drivers/cxl/trace.h  |  3 ++
 4 files changed, 96 insertions(+), 1 deletion(-)

diff --git a/.clang-format b/.clang-format
index 55f628f21722..96c282b63e7b 100644
--- a/.clang-format
+++ b/.clang-format
@@ -171,6 +171,7 @@ ForEachMacros:
   - 'for_each_cpu_wrap'
   - 'for_each_cxl_decoder_target'
   - 'for_each_cxl_endpoint'
+  - 'for_each_cxl_endpoint_hb'
   - 'for_each_dapm_widgets'
   - 'for_each_dev_addr'
   - 'for_each_dev_scope'
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 509b20375e0e..63554c9cebf0 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -303,6 +303,7 @@ struct cxl_port {
  * @port: reference to cxl_port that contains this downstream port
  * @list: node for a cxl_port's list of cxl_dport instances
  * @root_port_link: node for global list of root ports
+ * @verify_link: node used for hb root port verification
  */
 struct cxl_dport {
 	struct device *dport;
@@ -311,6 +312,8 @@ struct cxl_dport {
 	struct cxl_port *port;
 	struct list_head list;
 	struct list_head root_port_link;
+
+	struct list_head verify_link;
 };
 
 bool is_cxl_region(struct device *dev);
diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
index 53442de33d11..ecf453fd3257 100644
--- a/drivers/cxl/region.c
+++ b/drivers/cxl/region.c
@@ -4,6 +4,7 @@
 #include <linux/genalloc.h>
 #include <linux/device.h>
 #include <linux/module.h>
+#include <linux/sort.h>
 #include <linux/pci.h>
 #include "cxlmem.h"
 #include "region.h"
@@ -30,6 +31,11 @@
 	for (idx = 0, ep = (region)->targets[idx]; idx < region_ways(region);  \
 	     idx++, ep = (region)->targets[idx])
 
+#define for_each_cxl_endpoint_hb(ep, region, hb, idx)                          \
+	for (idx = 0, (ep) = (region)->targets[idx];                           \
+	     idx < region_ways(region); idx++, (ep) = (region)->targets[idx])  \
+		if (get_hostbridge(ep) == (hb))
+
 #define for_each_cxl_decoder_target(target, decoder, idx)                      \
 	for (idx = 0, target = (decoder)->target[idx];                         \
 	     idx < (decoder)->nr_targets;                                      \
@@ -261,6 +267,29 @@ static bool region_xhb_config_valid(const struct cxl_region *region,
 	return true;
 }
 
+static int get_num_root_ports(const struct cxl_region *region)
+{
+	struct cxl_memdev *endpoint;
+	struct cxl_dport *dport, *tmp;
+	int num_root_ports = 0;
+	LIST_HEAD(root_ports);
+	int idx;
+
+	for_each_cxl_endpoint(endpoint, region, idx) {
+		struct cxl_dport *root_port = endpoint->root_port;
+
+		if (list_empty(&root_port->verify_link)) {
+			list_add_tail(&root_port->verify_link, &root_ports);
+			num_root_ports++;
+		}
+	}
+
+	list_for_each_entry_safe(dport, tmp, &root_ports, verify_link)
+		list_del_init(&dport->verify_link);
+
+	return num_root_ports;
+}
+
 /**
  * region_hb_rp_config_valid() - determine root port ordering is correct
  * @cfmws: CFMWS decoder for this @region
@@ -274,7 +303,66 @@ static bool region_xhb_config_valid(const struct cxl_region *region,
 static bool region_hb_rp_config_valid(const struct cxl_region *region,
 				      const struct cxl_decoder *cfmws)
 {
-	/* TODO: */
+	const int num_root_ports = get_num_root_ports(region);
+	struct cxl_port *hbs[CXL_DECODER_MAX_INTERLEAVE];
+	int hb_count, i;
+
+	hb_count = get_unique_hostbridges(region, hbs);
+
+	/*
+	 * Are all devices in this region on the same CXL Host Bridge
+	 * Root Port?
+	 */
+	if (num_root_ports == 1)
+		return true;
+
+	for (i = 0; i < hb_count; i++) {
+		struct cxl_port *hb = hbs[i];
+		struct cxl_dport *rp;
+		int position_mask;
+		int idx;
+
+		/*
+		 * Calculate the position mask: NumRootPorts = 2^PositionMask
+		 * for this region.
+		 *
+		 * XXX: pos_mask is actually (1 << PositionMask)  - 1
+		 */
+		position_mask = (1 << (ilog2(num_root_ports))) - 1;
+
+		/*
+		 * Calculate the PortGrouping for each device on this CXL Host
+		 * Bridge Root Port:
+		 * PortGrouping = RegionLabel.Position & PositionMask
+		 */
+		list_for_each_entry(rp, &hb->dports, list) {
+			struct cxl_memdev *ep;
+			int port_grouping = -1;
+
+			for_each_cxl_endpoint_hb(ep, region, hb, idx) {
+				if (ep->root_port != rp)
+					continue;
+
+				if (port_grouping == -1) {
+					port_grouping = idx & position_mask;
+					continue;
+				}
+
+				/*
+				 * Do all devices in the region connected to this CXL
+				 * Host Bridge Root Port have the same PortGrouping?
+				 */
+				if ((idx & position_mask) != port_grouping) {
+					trace_hb_rp_valid(region,
+							  "One or more devices are not connected to the correct Host Bridge Root Port\n");
+					return false;
+				}
+			}
+
+			/* TODO: Check switch programming */
+		}
+	}
+
 	return true;
 }
 
diff --git a/drivers/cxl/trace.h b/drivers/cxl/trace.h
index 4de47d1111ac..57fe9342817c 100644
--- a/drivers/cxl/trace.h
+++ b/drivers/cxl/trace.h
@@ -41,6 +41,9 @@ DEFINE_EVENT(cxl_region_template, allocation_failed,
 DEFINE_EVENT(cxl_region_template, xhb_valid,
 	     TP_PROTO(const struct cxl_region *region, char *status),
 	     TP_ARGS(region, status));
+DEFINE_EVENT(cxl_region_template, hb_rp_valid,
+	     TP_PROTO(const struct cxl_region *region, char *status),
+	     TP_ARGS(region, status));
 
 #endif /* if !defined (__CXL_TRACE_H__) || defined(TRACE_HEADER_MULTI_READ) */
 
-- 
2.33.1