net: ipa: minor update to handling of packet with status

Rearrange some comments and assignments made when handling a packet
that is received with status, aiming to improve understandability.

Use DIV_ROUND_CLOSEST() to get a better per-packet true size estimate.

Signed-off-by: Alex Elder <elder@linaro.org>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index 39ae0dd..c552421 100644 (file)
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -1213,12 +1213,11 @@ static void ipa_endpoint_status_parse(struct ipa_endpoint *endpoint,
                        continue;
                }
 
-               /* Compute the amount of buffer space consumed by the
-                * packet, including the status element.  If the hardware
-                * is configured to pad packet data to an aligned boundary,
-                * account for that.  And if checksum offload is is enabled
-                * a trailer containing computed checksum information will
-                * be appended.
+               /* Compute the amount of buffer space consumed by the packet,
+                * including the status element.  If the hardware is configured
+                * to pad packet data to an aligned boundary, account for that.
+                * And if checksum offload is enabled a trailer containing
+                * computed checksum information will be appended.
                 */
                align = endpoint->data->rx.pad_align ? : 1;
                len = le16_to_cpu(status->pkt_len);
@@ -1226,16 +1225,21 @@ static void ipa_endpoint_status_parse(struct ipa_endpoint *endpoint,
                if (endpoint->data->checksum)
                        len += sizeof(struct rmnet_map_dl_csum_trailer);
 
-               /* Charge the new packet with a proportional fraction of
-                * the unused space in the original receive buffer.
-                * XXX Charge a proportion of the *whole* receive buffer?
-                */
                if (!ipa_status_drop_packet(status)) {
-                       u32 extra = unused * len / total_len;
-                       void *data2 = data + sizeof(*status);
-                       u32 len2 = le16_to_cpu(status->pkt_len);
+                       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"
+                        * proportionately across all aggregated packets in the
+                        * buffer.
+                        */
+                       extra = DIV_ROUND_CLOSEST(unused * len, total_len);
                        ipa_endpoint_skb_copy(endpoint, data2, len2, extra);
                }