net: ipa: refactor status buffer parsing

The packet length encoded in an IPA packet status buffer is computed
more than once in ipa_endpoint_status_parse().  It is also checked
again in ipa_endpoint_status_skip(), which that function calls.

Compute the length once, and use that computed value later rather
than recomputing it.  Check for it being zero in the parse function
rather than in ipa_endpoint_status_skip().
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ipa/ipa_endpoint.c

@@ -1325,8 +1325,7 @@ static bool ipa_endpoint_status_skip(struct ipa_endpoint *endpoint,
 
 	if (!ipa_status_format_packet(status->opcode))
 		return true;
-	if (!status->pkt_len)
-		return true;
+
 	endpoint_id = u8_get_bits(status->endp_dst_idx,
 				  IPA_STATUS_DST_IDX_FMASK);
 	if (endpoint_id != endpoint->endpoint_id)
@@ -1394,6 +1393,7 @@ static void ipa_endpoint_status_parse(struct ipa_endpoint *endpoint,
 
 	while (resid) {
 		const struct ipa_status *status = data;
+		u32 length;
 		u32 align;
 		u32 len;
 
@@ -1405,7 +1405,8 @@ static void ipa_endpoint_status_parse(struct ipa_endpoint *endpoint,
 		}
 
 		/* Skip over status packets that lack packet data */
-		if (ipa_endpoint_status_skip(endpoint, status)) {
+		length = le16_to_cpu(status->pkt_len);
+		if (!length || ipa_endpoint_status_skip(endpoint, status)) {
 			data += sizeof(*status);
 			resid -= sizeof(*status);
 			continue;
@@ -1418,19 +1419,16 @@ static void ipa_endpoint_status_parse(struct ipa_endpoint *endpoint,
 		 * computed checksum information will be appended.
 		 */
 		align = endpoint->config.rx.pad_align ? : 1;
-		len = le16_to_cpu(status->pkt_len);
-		len = sizeof(*status) + ALIGN(len, align);
+		len = sizeof(*status) + ALIGN(length, align);
 		if (endpoint->config.checksum)
 			len += sizeof(struct rmnet_map_dl_csum_trailer);
 
 		if (!ipa_endpoint_status_drop(endpoint, status)) {
 			void *data2;
 			u32 extra;
-			u32 len2;
 
 			/* Client receives only packet data (no status) */
 			data2 = data + sizeof(*status);
-			len2 = le16_to_cpu(status->pkt_len);
 
 			/* Have the true size reflect the extra unused space in
 			 * the original receive buffer.  Distribute the "cost"
@@ -1438,7 +1436,7 @@ static void ipa_endpoint_status_parse(struct ipa_endpoint *endpoint,
 			 * buffer.
 			 */
 			extra = DIV_ROUND_CLOSEST(unused * len, total_len);
-			ipa_endpoint_skb_copy(endpoint, data2, len2, extra);
+			ipa_endpoint_skb_copy(endpoint, data2, length, extra);
 		}
 
 		/* Consume status and the full packet it describes */