drm/dp: Kill unused MST vcpi slot availability tracking

The avail_slots member in the MST topology manager is never updated to
reflect the available vcpi slots. The check is effectively against
total slots, 63. So, let's make that check obvious and remove
avail_slots. While at it, make debug messages more descriptive.

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Archit Taneja <architt@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Harry Wentland <Harry.wentland@amd.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1489648231-30700-3-git-send-email-dhinakaran.pandiyan@intel.com

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -2042,9 +2042,6 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
 			goto out_unlock;
 		}
 
-		/* max. time slots - one slot for MTP header */
-		mgr->avail_slots = 63;
-
 		/* add initial branch device at LCT 1 */
 		mstb = drm_dp_add_mst_branch_device(1, NULL);
 		if (mstb == NULL) {
@@ -2474,7 +2471,8 @@ int drm_dp_find_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr,
 
 	num_slots = DIV_ROUND_UP(pbn, mgr->pbn_div);
 
-	if (num_slots > mgr->avail_slots)
+	/* max. time slots - one slot for MTP header */
+	if (num_slots > 63)
 		return -ENOSPC;
 	return num_slots;
 }
@@ -2488,7 +2486,8 @@ static int drm_dp_init_vcpi(struct drm_dp_mst_topology_mgr *mgr,
 
 	num_slots = DIV_ROUND_UP(pbn, mgr->pbn_div);
 
-	if (num_slots > mgr->avail_slots)
+	/* max. time slots - one slot for MTP header */
+	if (num_slots > 63)
 		return -ENOSPC;
 
 	vcpi->pbn = pbn;
@@ -2527,10 +2526,12 @@ bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp
 
 	ret = drm_dp_init_vcpi(mgr, &port->vcpi, pbn);
 	if (ret) {
-		DRM_DEBUG_KMS("failed to init vcpi %d %d %d\n", DIV_ROUND_UP(pbn, mgr->pbn_div), mgr->avail_slots, ret);
+		DRM_DEBUG_KMS("failed to init vcpi slots=%d max=63 ret=%d\n",
+				DIV_ROUND_UP(pbn, mgr->pbn_div), ret);
 		goto out;
 	}
-	DRM_DEBUG_KMS("initing vcpi for %d %d\n", pbn, port->vcpi.num_slots);
+	DRM_DEBUG_KMS("initing vcpi for pbn=%d slots=%d\n",
+			pbn, port->vcpi.num_slots);
 	*slots = port->vcpi.num_slots;
 
 	drm_dp_put_port(port);

include/drm/drm_dp_mst_helper.h

@@ -480,11 +480,6 @@ struct drm_dp_mst_topology_mgr {
 	 */
 	int pbn_div;
 
-	/**
-	 * @avail_slots: Still available slots that can be allocated.
-	 */
-	int avail_slots;
-
 	/**
 	 * @qlock: protects @tx_msg_downq, the &drm_dp_mst_branch.txslost and
 	 * &drm_dp_sideband_msg_tx.state once they are queued