net: hns3: support tx-scatter-gather-fraglist feature

The hardware supports up to 8 TX BD for non-tso skb and up to
63 TX BD for TSO skb. Currently, the hns3 driver supports RX skb
with fraglist when HW GRO is enabled, when the stack forwards a
RX skb with fraglist, the stack need to linearize the skb before
sending to other interface without TX fraglist support.

This patch adds support for TX fraglist. The performance increases
from 1 GByte to 1.5 GByte for one iperf TCP stream during
forwarding test after this patch. BTW, the minimum BD number of
ring should be updated to 72 for supporting TX fraglist.

This patch also changes the error handling of some function that
called by hns3_fill_desc, which returns BD num when there is no
error, change some macro to more meaningful name.
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>

drivers/net/ethernet/hisilicon/hns3/hns3_enet.h

@@ -76,7 +76,7 @@ enum hns3_nic_state {
 #define HNS3_RING_NAME_LEN			16
 #define HNS3_BUFFER_SIZE_2048			2048
 #define HNS3_RING_MAX_PENDING			32760
-#define HNS3_RING_MIN_PENDING			24
+#define HNS3_RING_MIN_PENDING			72
 #define HNS3_RING_BD_MULTIPLE			8
 /* max frame size of mac */
 #define HNS3_MAC_MAX_FRAME			9728
@@ -195,9 +195,13 @@ enum hns3_nic_state {
 #define HNS3_VECTOR_INITED			1
 
 #define HNS3_MAX_BD_SIZE			65535
-#define HNS3_MAX_BD_NUM_NORMAL			8
-#define HNS3_MAX_BD_NUM_TSO			63
-#define HNS3_MAX_BD_PER_PKT			MAX_SKB_FRAGS
+#define HNS3_MAX_NON_TSO_BD_NUM			8U
+#define HNS3_MAX_TSO_BD_NUM			63U
+#define HNS3_MAX_TSO_SIZE \
+	(HNS3_MAX_BD_SIZE * HNS3_MAX_TSO_BD_NUM)
+
+#define HNS3_MAX_NON_TSO_SIZE \
+	(HNS3_MAX_BD_SIZE * HNS3_MAX_NON_TSO_BD_NUM)
 
 #define HNS3_VECTOR_GL0_OFFSET			0x100
 #define HNS3_VECTOR_GL1_OFFSET			0x200