[PATCH v4 3/3] drm/xe/uapi: Augment query ioctl to allow for fabric

[David Kershner]

UMDs need to understand if two devices have connectivity, and what
that connectivity is.

Add to the query_ioctl the ability to determine if a fabric id and
current device have connectivity.

Signed-off-by: David Kershner <david.kershner at intel.com>
---
 drivers/gpu/drm/xe/xe_query.c | 54 +++++++++++++++++++++++++++++++++++
 include/uapi/drm/xe_drm.h     | 26 +++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_query.c b/drivers/gpu/drm/xe/xe_query.c
index 9b35673b286c..b7366acfcfd8 100644
--- a/drivers/gpu/drm/xe/xe_query.c
+++ b/drivers/gpu/drm/xe/xe_query.c
@@ -6,10 +6,12 @@
 #include "xe_query.h"
 
 #include <linux/nospec.h>
+#include <linux/overflow.h>
 #include <linux/sched/clock.h>
 
 #include <drm/ttm/ttm_placement.h>
 #include <drm/xe_drm.h>
+#include <drm/xelink_platform.h>
 
 #include "regs/xe_engine_regs.h"
 #include "xe_bo.h"
@@ -104,6 +106,57 @@ __read_timestamps(struct xe_gt *gt,
 	*engine_ts = (u64)upper << 32 | lower;
 }
 
+static int
+query_fabric_connectivity(struct xe_device *xe,
+			  struct drm_xe_device_query *query)
+{
+	struct drm_xe_query_fabric_info __user *query_ptr;
+	struct drm_xe_query_fabric_info info;
+	struct query_info *qi;
+	u32 latency = 0;
+	int cnt;
+	int i;
+
+	query_ptr = u64_to_user_ptr(query->data);
+	if (copy_from_user(&info, query_ptr, sizeof(info)))
+		return -EFAULT;
+
+	info.bandwidth = 0;
+	info.latency = 0;
+
+	if (info.fabric_id == xe->xelink.xelink_id)
+		goto done;
+
+	qi = xe->xelink.ops->connectivity_query(xe->xelink.handle, info.fabric_id);
+	if (IS_ERR(qi))
+		goto done;
+	/*
+	 * Examine the query information for connectivity.
+	 * Minimum bandwidth value is the bandwidth, 0 == no connectivity
+	 * Latency is averaged.
+	 */
+	cnt = qi->src_cnt * qi->dst_cnt;
+	if (!cnt) {
+		kfree(qi);
+		return -ENXIO;
+	}
+
+	info.bandwidth = 0xffff;
+	for (i = 0; i < cnt; i++) {
+		info.bandwidth = min(qi->sd2sd[i].bandwidth, info.bandwidth);
+		XE_WARN_ON(check_add_overflow(latency, qi->sd2sd[i].latency,
+					      &latency));
+	}
+
+	info.latency = latency / cnt;
+
+	kfree(qi);
+done:
+	if (copy_to_user(query_ptr, &info, sizeof(info)))
+		return -EFAULT;
+	return 0;
+}
+
 static int
 query_engine_cycles(struct xe_device *xe,
 		    struct drm_xe_device_query *query)
@@ -529,6 +582,7 @@ static int (* const xe_query_funcs[])(struct xe_device *xe,
 	query_hwconfig,
 	query_gt_topology,
 	query_engine_cycles,
+	query_fabric_connectivity,
 };
 
 int xe_query_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
index 9fa3ae324731..b2d4af6729e1 100644
--- a/include/uapi/drm/xe_drm.h
+++ b/include/uapi/drm/xe_drm.h
@@ -574,6 +574,31 @@ struct drm_xe_query_engine_cycles {
 	__u64 cpu_delta;
 };
 
+/**
+ * struct drm_xe_query_fabric_info
+ *
+ * With the given fabric id, query fabric info wrt the device.
+ * Higher bandwidth is better.  0 means no fabric.
+ * Latency is averaged latency (from all paths)
+ *
+ * fabric_id can be obtained from
+ *    /sys/class/drm/cardx/device/xelink.y/xelink_fabric_id
+ * Bandwidth is in Gigabits per second (max value of 8 * 4 * 90)
+ *    8 possible ports
+ *    4 lanes max per port
+ *   90 gigabits per lane
+ * Latency is in tenths of path length. 10 == 1 fabric link between src and dst
+ *   POR is max 1 link (zero hops).
+ */
+struct drm_xe_query_fabric_info {
+	/** @fabric_id: Fabric id associated with info */
+	__u32 fabric_id;
+	/** @bandwidth: minimum bandwidth of all connected ports, if 0 no fabric */
+	__u16 bandwidth;
+	/** @latency: latency averaged across all connected ports. */
+	__u16 latency;
+};
+
 /**
  * struct drm_xe_device_query - Input of &DRM_IOCTL_XE_DEVICE_QUERY - main
  * structure to query device information
@@ -643,6 +668,7 @@ struct drm_xe_device_query {
 #define DRM_XE_DEVICE_QUERY_HWCONFIG		4
 #define DRM_XE_DEVICE_QUERY_GT_TOPOLOGY		5
 #define DRM_XE_DEVICE_QUERY_ENGINE_CYCLES	6
+#define DRM_XE_DEVICE_QUERY_FABRIC_INFO		7
 	/** @query: The type of data to query */
 	__u32 query;
 
-- 
2.38.1