drm/xe/guc: Bump the G2H queue size to account for page faults

With the increase in the size of the recoverable page fault
queue, we want to ensure the initial messages from GuC in
the G2H buffer have space while we transfer those out to the
actual pf_queue. Bump the G2H queue size to account for this
increase in the pf_queue size.
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/4c2b6974801bcffd8a010d838c8733fa4092573d.1723862633.git.stuart.summers@intel.com

drivers/gpu/drm/xe/xe_guc_ct.c

@@ -105,12 +105,20 @@ ct_to_xe(struct xe_guc_ct *ct)
  * enough space to avoid backpressure on the driver. We increase the size
  * of the receive buffer (relative to the send) to ensure a G2H response
  * CTB has a landing spot.
+ *
+ * In addition to submissions, the G2H buffer needs to be able to hold
+ * enough space for recoverable page fault notifications. The number of
+ * page faults is interrupt driven and can be as much as the number of
+ * compute resources available. However, most of the actual work for these
+ * is in a separate page fault worker thread. Therefore we only need to
+ * make sure the queue has enough space to handle all of the submissions
+ * and responses and an extra buffer for incoming page faults.
  */
 
 #define CTB_DESC_SIZE		ALIGN(sizeof(struct guc_ct_buffer_desc), SZ_2K)
 #define CTB_H2G_BUFFER_SIZE	(SZ_4K)
-#define CTB_G2H_BUFFER_SIZE	(4 * CTB_H2G_BUFFER_SIZE)
-#define G2H_ROOM_BUFFER_SIZE	(CTB_G2H_BUFFER_SIZE / 4)
+#define CTB_G2H_BUFFER_SIZE	(SZ_128K)
+#define G2H_ROOM_BUFFER_SIZE	(CTB_G2H_BUFFER_SIZE / 2)
 
 /**
  * xe_guc_ct_queue_proc_time_jiffies - Return maximum time to process a full