net: qualcomm: rmnet: Define the MAPv4 packet formats

The MAPv4 packet format adds support for RX / TX checksum offload.
For a bi-directional UDP stream at a rate of 570 / 146 Mbps, roughly
10% CPU cycles are saved.

For receive path, there is a checksum trailer appended to the end of
the MAP packet. The valid field indicates if hardware has computed
the checksum. csum_start_offset indicates the offset from the start
of the IP header from which hardware has computed checksum.
csum_length is the number of bytes over which the checksum was
computed and the resulting value is csum_value.

In the transmit path, a header is appended between the end of the MAP
header and the start of the IP packet. csum_start_offset is the offset
in bytes from which hardware will compute the checksum if the
csum_enabled bit is set. udp_ip4_ind indicates if the checksum
value of 0 is valid or not. csum_insert_offset is the offset from the
csum_start_offset where hardware will insert the computed checksum.

The use of this additional packet format for checksum offload is
explained in subsequent patches.

Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h

@@ -47,6 +47,22 @@ struct rmnet_map_header {
 	u16 pkt_len;
 }  __aligned(1);
 
+struct rmnet_map_dl_csum_trailer {
+	u8  reserved1;
+	u8  valid:1;
+	u8  reserved2:7;
+	u16 csum_start_offset;
+	u16 csum_length;
+	__be16 csum_value;
+} __aligned(1);
+
+struct rmnet_map_ul_csum_header {
+	__be16 csum_start_offset;
+	u16 csum_insert_offset:14;
+	u16 udp_ip4_ind:1;
+	u16 csum_enabled:1;
+} __aligned(1);
+
 #define RMNET_MAP_GET_MUX_ID(Y) (((struct rmnet_map_header *) \
 				 (Y)->data)->mux_id)
 #define RMNET_MAP_GET_CD_BIT(Y) (((struct rmnet_map_header *) \

drivers/net/ethernet/qualcomm/rmnet/rmnet_private.h

@@ -21,6 +21,8 @@
 /* Constants */
 #define RMNET_INGRESS_FORMAT_DEAGGREGATION      BIT(0)
 #define RMNET_INGRESS_FORMAT_MAP_COMMANDS       BIT(1)
+#define RMNET_INGRESS_FORMAT_MAP_CKSUMV4        BIT(2)
+#define RMNET_EGRESS_FORMAT_MAP_CKSUMV4         BIT(3)
 
 /* Replace skb->dev to a virtual rmnet device and pass up the stack */
 #define RMNET_EPMODE_VND (1)