arch/arm/ameba: tune WHC Wi-Fi TCP throughput on both boards

Tune the TCP stack and driver resources for the WHC Wi-Fi data path on both
rtl8720f_evb and pke8721daf (NuttX runs on the application core; the Wi-Fi MAC
runs on a companion core reached over an on-chip IPC):

- Cap the advertised TCP receive window (NET_RECV_BUFSIZE=10000) to about the
  out-of-order reassembly capacity and bound in-flight TX
  (NET_SEND_BUFSIZE=16384).  The stock unbounded window/queue let the peer and
  the local stack burst far more than the Wi-Fi path can smooth, causing
  bursty loss/reordering and RTO stalls (RX), and starving incoming-ACK
  processing so the peer window collapses and spurious retransmits tear the
  link down (TX).
- Keep out-of-order reassembly (NET_TCP_OUT_OF_ORDER) but disable selective
  ACK.  PR #19353 enabled NET_TCP_SELECTIVE_ACK on both boards; on the lossy
  Wi-Fi TX path the sender-side selective-ACK recovery does not reliably
  repair multi-segment holes and stalls TX, so NewReno with out-of-order
  reassembly is used instead -- same steady-state throughput, robust recovery.
- Widen IOB buffers to 512 bytes; the window and out-of-order buffers draw
  from the shared IOB pool at run time and add no static memory.
- Drop the busy-wait retry in the transmit path (the send-buffer cap makes it
  dead code) and lower the forced host TX skb count (skb_num_ap) to 8, which
  covers the NP's transient TX backlog without over-reserving AP heap.

Signed-off-by: raul_chen <raul_chen@realsil.com.cn>

arch/arm/src/common/ameba/ameba_wlan.c

@@ -226,8 +226,13 @@ static int ameba_wlan_transmit(struct netdev_lowerhalf_s *dev,
 
   if (ret != 0)
     {
-      /* NP skb pool full: let the upper half recycle the packet and pause
-       * the poll (backpressure).  Do NOT free here.
+      /* NP host skb pool full: recycle the packet (do NOT free) and
+       * let the upper half pause the poll -- genuine backpressure.
+       * This stays off the hot path because CONFIG_NET_SEND_BUFSIZE
+       * bounds a stream's in-flight data and the NP drains at line
+       * rate, so the transient host skb backlog stays well under the
+       * pool (skb_num_ap).  A momentary full pool just pauses here and
+       * resumes on the next poll.
        */
 
       return -EIO;

arch/arm/src/common/ameba/wifi/ameba_wifi.c

@@ -108,17 +108,19 @@ int ameba_wifi_start(void)
       g_rtw_task_size.ipc_unblk_api_task = 4096;
     }
 
-  /* Host TX skb pool: the SDK default (4) is too small for sustained TCP
-   * TX.  The pool drains, whc_ipc_host_send() returns -2 (drops the frame),
-   * TCP retransmits, and under load the retransmits exhaust and the link is
-   * torn down (send -> ENOTCONN).  UDP tolerates the drops so is unaffected.
-   * A modest pool keeps TCP TX stable; 16 skbs ~= 27 KB of AP heap (vs 53 KB
-   * at 32).
+  /* Host TX skb pool: the SDK default (4) is too small for sustained
+   * TCP TX (the pool drains, whc_ipc_host_send() returns -2, the frame
+   * is dropped and TCP stalls).  CONFIG_NET_SEND_BUFSIZE now bounds a
+   * stream's in-flight data and the NP drains at line rate, so the pool
+   * only has to cover the NP's transient TX backlog, not the whole
+   * window -- 8 skbs (~13 KB of AP heap) is enough here, well above the
+   * SDK stack's own high-throughput profile of 5.  Raise if bulk TX
+   * regresses.
    */
 
-  if (wifi_user_config.skb_num_ap < 16)
+  if (wifi_user_config.skb_num_ap < 8)
     {
-      wifi_user_config.skb_num_ap = 16;
+      wifi_user_config.skb_num_ap = 8;
     }
 
   whc_ipc_host_init();

boards/arm/rtl8720f/rtl8720f_evb/configs/nsh/defconfig

@@ -28,7 +28,7 @@ CONFIG_FS_PROCFS=y
 CONFIG_FS_TMPFS=y
 CONFIG_IDLETHREAD_STACKSIZE=4096
 CONFIG_INIT_ENTRYPOINT="nsh_main"
-CONFIG_IOB_BUFSIZE=400
+CONFIG_IOB_BUFSIZE=512
 CONFIG_IOB_NBUFFERS=100
 CONFIG_IOB_NCHAINS=36
 CONFIG_IOB_THROTTLE=40
@@ -50,11 +50,14 @@ CONFIG_NET_ARP_IPIN=y
 CONFIG_NET_BROADCAST=y
 CONFIG_NET_ETH_PKTSIZE=1514
 CONFIG_NET_ICMP_SOCKET=y
+CONFIG_NET_RECV_BUFSIZE=10000
+CONFIG_NET_SEND_BUFSIZE=16384
 CONFIG_NET_TCP=y
 CONFIG_NET_TCP_DELAYED_ACK=y
 CONFIG_NET_TCP_KEEPALIVE=y
 CONFIG_NET_TCP_NOTIFIER=y
-CONFIG_NET_TCP_SELECTIVE_ACK=y
+CONFIG_NET_TCP_OUT_OF_ORDER=y
+CONFIG_NET_TCP_OUT_OF_ORDER_BUFSIZE=10000
 CONFIG_NET_TCP_WRITE_BUFFERS=y
 CONFIG_NET_UDP=y
 CONFIG_NSH_BUILTIN_APPS=y

boards/arm/rtl8721dx/pke8721daf/configs/nsh/defconfig

@@ -28,7 +28,7 @@ CONFIG_FS_PROCFS=y
 CONFIG_FS_TMPFS=y
 CONFIG_IDLETHREAD_STACKSIZE=4096
 CONFIG_INIT_ENTRYPOINT="nsh_main"
-CONFIG_IOB_BUFSIZE=400
+CONFIG_IOB_BUFSIZE=512
 CONFIG_IOB_NBUFFERS=100
 CONFIG_IOB_NCHAINS=36
 CONFIG_IOB_THROTTLE=40
@@ -50,11 +50,14 @@ CONFIG_NET_ARP_IPIN=y
 CONFIG_NET_BROADCAST=y
 CONFIG_NET_ETH_PKTSIZE=1514
 CONFIG_NET_ICMP_SOCKET=y
+CONFIG_NET_RECV_BUFSIZE=10000
+CONFIG_NET_SEND_BUFSIZE=16384
 CONFIG_NET_TCP=y
 CONFIG_NET_TCP_DELAYED_ACK=y
 CONFIG_NET_TCP_KEEPALIVE=y
 CONFIG_NET_TCP_NOTIFIER=y
-CONFIG_NET_TCP_SELECTIVE_ACK=y
+CONFIG_NET_TCP_OUT_OF_ORDER=y
+CONFIG_NET_TCP_OUT_OF_ORDER_BUFSIZE=10000
 CONFIG_NET_TCP_WRITE_BUFFERS=y
 CONFIG_NET_UDP=y
 CONFIG_NSH_BUILTIN_APPS=y