drm/amd/doc: Add XGMI sysfs documentation

Acked-by: Slava Abramov <slava.abramov@amd.com>
Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Documentation/gpu/amdgpu.rst

@@ -70,6 +70,15 @@ Interrupt Handling
 .. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
    :internal:
 
+AMDGPU XGMI Support
+===================
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
+   :doc: AMDGPU XGMI Support
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
+   :internal:
+
 GPU Power/Thermal Controls and Monitoring
 =========================================
 

drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c

@@ -40,6 +40,34 @@ void *amdgpu_xgmi_hive_try_lock(struct amdgpu_hive_info *hive)
 	return &hive->device_list;
 }
 
+/**
+ * DOC: AMDGPU XGMI Support
+ *
+ * XGMI is a high speed interconnect that joins multiple GPU cards
+ * into a homogeneous memory space that is organized by a collective
+ * hive ID and individual node IDs, both of which are 64-bit numbers.
+ *
+ * The file xgmi_device_id contains the unique per GPU device ID and
+ * is stored in the /sys/class/drm/card${cardno}/device/ directory.
+ *
+ * Inside the device directory a sub-directory 'xgmi_hive_info' is
+ * created which contains the hive ID and the list of nodes.
+ *
+ * The hive ID is stored in:
+ *   /sys/class/drm/card${cardno}/device/xgmi_hive_info/xgmi_hive_id
+ *
+ * The node information is stored in numbered directories:
+ *   /sys/class/drm/card${cardno}/device/xgmi_hive_info/node${nodeno}/xgmi_device_id
+ *
+ * Each device has their own xgmi_hive_info direction with a mirror
+ * set of node sub-directories.
+ *
+ * The XGMI memory space is built by contiguously adding the power of
+ * two padded VRAM space from each node to each other.
+ *
+ */
+
+
 static ssize_t amdgpu_xgmi_show_hive_id(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {