nfp: flower: refine the use of circular buffer

The current use of circular buffer to manage stats_context_id is
very obscure, and it will cause problem if its element size is
not power of two. So change the use more straightforward and
scalable, and also change that for mask_id to keep consistency.
Signed-off-by: Yinjun Zhang <yinjun.zhang@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/1639618621-5857-1-git-send-email-yinjun.zhang@corigine.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/netronome/nfp/flower/metadata.c

@@ -43,15 +43,14 @@ static int nfp_release_stats_entry(struct nfp_app *app, u32 stats_context_id)
 	struct circ_buf *ring;
 
 	ring = &priv->stats_ids.free_list;
-	/* Check if buffer is full. */
-	if (!CIRC_SPACE(ring->head, ring->tail,
-			priv->stats_ring_size * NFP_FL_STATS_ELEM_RS -
-			NFP_FL_STATS_ELEM_RS + 1))
+	/* Check if buffer is full, stats_ring_size must be power of 2 */
+	if (!CIRC_SPACE(ring->head, ring->tail, priv->stats_ring_size))
 		return -ENOBUFS;
 
-	memcpy(&ring->buf[ring->head], &stats_context_id, NFP_FL_STATS_ELEM_RS);
-	ring->head = (ring->head + NFP_FL_STATS_ELEM_RS) %
-		     (priv->stats_ring_size * NFP_FL_STATS_ELEM_RS);
+	/* Each increment of head represents size of NFP_FL_STATS_ELEM_RS */
+	memcpy(&ring->buf[ring->head * NFP_FL_STATS_ELEM_RS],
+	       &stats_context_id, NFP_FL_STATS_ELEM_RS);
+	ring->head = (ring->head + 1) & (priv->stats_ring_size - 1);
 
 	return 0;
 }
@@ -86,11 +85,14 @@ static int nfp_get_stats_entry(struct nfp_app *app, u32 *stats_context_id)
 		return -ENOENT;
 	}
 
-	memcpy(&temp_stats_id, &ring->buf[ring->tail], NFP_FL_STATS_ELEM_RS);
+	/* Each increment of tail represents size of NFP_FL_STATS_ELEM_RS */
+	memcpy(&temp_stats_id, &ring->buf[ring->tail * NFP_FL_STATS_ELEM_RS],
+	       NFP_FL_STATS_ELEM_RS);
 	*stats_context_id = temp_stats_id;
-	memcpy(&ring->buf[ring->tail], &freed_stats_id, NFP_FL_STATS_ELEM_RS);
-	ring->tail = (ring->tail + NFP_FL_STATS_ELEM_RS) %
-		     (priv->stats_ring_size * NFP_FL_STATS_ELEM_RS);
+	memcpy(&ring->buf[ring->tail * NFP_FL_STATS_ELEM_RS], &freed_stats_id,
+	       NFP_FL_STATS_ELEM_RS);
+	/* stats_ring_size must be power of 2 */
+	ring->tail = (ring->tail + 1) & (priv->stats_ring_size - 1);
 
 	return 0;
 }
@@ -138,13 +140,18 @@ static int nfp_release_mask_id(struct nfp_app *app, u8 mask_id)
 	struct circ_buf *ring;
 
 	ring = &priv->mask_ids.mask_id_free_list;
-	/* Checking if buffer is full. */
+	/* Checking if buffer is full,
+	 * NFP_FLOWER_MASK_ENTRY_RS must be power of 2
+	 */
 	if (CIRC_SPACE(ring->head, ring->tail, NFP_FLOWER_MASK_ENTRY_RS) == 0)
 		return -ENOBUFS;
 
-	memcpy(&ring->buf[ring->head], &mask_id, NFP_FLOWER_MASK_ELEMENT_RS);
-	ring->head = (ring->head + NFP_FLOWER_MASK_ELEMENT_RS) %
-		     (NFP_FLOWER_MASK_ENTRY_RS * NFP_FLOWER_MASK_ELEMENT_RS);
+	/* Each increment of head represents size of
+	 * NFP_FLOWER_MASK_ELEMENT_RS
+	 */
+	memcpy(&ring->buf[ring->head * NFP_FLOWER_MASK_ELEMENT_RS], &mask_id,
+	       NFP_FLOWER_MASK_ELEMENT_RS);
+	ring->head = (ring->head + 1) & (NFP_FLOWER_MASK_ENTRY_RS - 1);
 
 	priv->mask_ids.last_used[mask_id] = ktime_get();
 
@@ -171,7 +178,11 @@ static int nfp_mask_alloc(struct nfp_app *app, u8 *mask_id)
 	if (ring->head == ring->tail)
 		goto err_not_found;
 
-	memcpy(&temp_id, &ring->buf[ring->tail], NFP_FLOWER_MASK_ELEMENT_RS);
+	/* Each increment of tail represents size of
+	 * NFP_FLOWER_MASK_ELEMENT_RS
+	 */
+	memcpy(&temp_id, &ring->buf[ring->tail * NFP_FLOWER_MASK_ELEMENT_RS],
+	       NFP_FLOWER_MASK_ELEMENT_RS);
 	*mask_id = temp_id;
 
 	reuse_timeout = ktime_add_ns(priv->mask_ids.last_used[*mask_id],
@@ -180,9 +191,10 @@ static int nfp_mask_alloc(struct nfp_app *app, u8 *mask_id)
 	if (ktime_before(ktime_get(), reuse_timeout))
 		goto err_not_found;
 
-	memcpy(&ring->buf[ring->tail], &freed_id, NFP_FLOWER_MASK_ELEMENT_RS);
-	ring->tail = (ring->tail + NFP_FLOWER_MASK_ELEMENT_RS) %
-		     (NFP_FLOWER_MASK_ENTRY_RS * NFP_FLOWER_MASK_ELEMENT_RS);
+	memcpy(&ring->buf[ring->tail * NFP_FLOWER_MASK_ELEMENT_RS], &freed_id,
+	       NFP_FLOWER_MASK_ELEMENT_RS);
+	/* NFP_FLOWER_MASK_ENTRY_RS must be power of 2 */
+	ring->tail = (ring->tail + 1) & (NFP_FLOWER_MASK_ENTRY_RS - 1);
 
 	return 0;