Retry CH569 SuperSpeed training and fix net_lwip_webserver EP0 size

Two fixes found bringing up SuperSpeed on a Renesas uPD720201-based hub:

- dcd_ch56x_usb30: retry link training with a fresh detect cycle every
  second fallback-timer tick (4 ticks total) before switching to the
  USB2 fallback. Some hubs only complete Polling on a re-attempt; with
  a single continuous attempt the link reached U0 rarely and the port
  fell back to high speed almost every boot.

- net_lwip_webserver: CFG_TUD_ENDPOINT0_SIZE was left at plain 64, so
  usbd chunked EP0 data at 64 bytes; on a 512-mps SuperSpeed control
  endpoint the first chunk is a short packet, the host ends the data
  stage early and the status stage deadlocks until timeout ("can't
  read configurations, error -110"). Use the SuperSpeed-aware size and
  clamp the device-qualifier bMaxPacketSize0 like the other examples.

Validated on HydraUSB3: NCM enumerates at 5000M reliably across warm
reboots; lwiperf over SuperSpeed measures 51 Mbit/s device RX (TCP
window bound; 33 Mbit/s on the high-speed fallback), MSC 169/136 MB/s.
Full example sweep, 65/65 unit tests, pre-commit clean.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_019MRGjBT2NBkCoWwyDT4LaE

3 files changed, 16 insertions, 4 deletions

diff --git a/examples/device/net_lwip_webserver/src/tusb_config.h b/examples/device/net_lwip_webserver/src/tusb_config.h
index 2ff68a356..ef5d5f622 100644
--- a/examples/device/net_lwip_webserver/src/tusb_config.h
+++ b/examples/device/net_lwip_webserver/src/tusb_config.h
@@ -149,7 +149,7 @@ extern "C" {
 //--------------------------------------------------------------------
 
 #ifndef CFG_TUD_ENDPOINT0_SIZE
-  #define CFG_TUD_ENDPOINT0_SIZE 64
+  #define CFG_TUD_ENDPOINT0_SIZE (TUD_OPT_SUPER_SPEED ? 512 : 64) // SuperSpeed EP0 is fixed at 512
 #endif
 
 //------------- CLASS -------------//
diff --git a/examples/device/net_lwip_webserver/src/usb_descriptors.c b/examples/device/net_lwip_webserver/src/usb_descriptors.c
index 10c003c75..a5c2da6ab 100644
--- a/examples/device/net_lwip_webserver/src/usb_descriptors.c
+++ b/examples/device/net_lwip_webserver/src/usb_descriptors.c
@@ -346,7 +346,7 @@ static tusb_desc_device_qualifier_t const desc_device_qualifier = {
   .bDeviceSubClass    = MISC_SUBCLASS_COMMON,
   .bDeviceProtocol    = MISC_PROTOCOL_IAD,
 
-  .bMaxPacketSize0    = CFG_TUD_ENDPOINT0_SIZE,
+  .bMaxPacketSize0    = EP0_SIZE_FSHS,
   .bNumConfigurations = CONFIG_ID_COUNT,
   .bReserved          = 0x00
 };
diff --git a/src/portable/wch/dcd_ch56x_usb30.c b/src/portable/wch/dcd_ch56x_usb30.c
index f9c7fded7..cc14a86ce 100644
--- a/src/portable/wch/dcd_ch56x_usb30.c
+++ b/src/portable/wch/dcd_ch56x_usb30.c
@@ -103,6 +103,7 @@ static volatile bool _lmp_pending;        // send LMP PORT_CAPABILITY at next li
 // timer. One way: returning to SuperSpeed after fallback requires a new dcd_init (or power cycle).
 enum { FB_USB3_TRAINING = 0, FB_USB3_OFF, FB_USB3_UP, FB_USB2_ACTIVE };
 static volatile uint8_t _fb_state;
+static uint8_t _fb_train_ticks; // training timer expiries; a fresh detect cycle every 2nd tick
 
 static void fallback_timer_stop(void) {
   R8_TMR0_INTER_EN = 0;
@@ -111,9 +112,10 @@ static void fallback_timer_stop(void) {
 }
 
 static void fallback_timer_start(void) {
+  _fb_train_ticks = 0;
   R8_TMR0_CTRL_MOD = RB_TMR_ALL_CLEAR;
   // TMR0 counts 26 bits: CNT_END must stay below 2^26 (67108864). 0.55 s per expiry at
-  // 120 MHz, ~1.1 s total before USB2 comes up
+  // 120 MHz; training gets several expiries (with re-attempts) before USB2 comes up
   R32_TMR0_CNT_END = 66000000;
   R8_TMR0_INT_FLAG = RB_TMR_IF_CYC_END;
   R8_TMR0_INTER_EN = RB_TMR_IE_CYC_END;
@@ -543,7 +545,17 @@ void dcd_int_handler(uint8_t rhport) {
   if (R8_TMR0_INT_FLAG & RB_TMR_IF_CYC_END) {
     R8_TMR0_INT_FLAG = RB_TMR_IF_CYC_END;
     if (_fb_state == FB_USB3_TRAINING) {
-      // first expiry: shut USB3 down so the host sees a disconnect
+      // Retry SuperSpeed training with a fresh detect cycle a few times before giving up:
+      // some hubs (e.g. Renesas uPD720201's) only complete training on a re-attempt
+      _fb_train_ticks++;
+      if (_fb_train_ticks < 4) {
+        if ((_fb_train_ticks & 1u) == 0) {
+          usb30_hw_deinit();
+          usb30_hw_init();
+        }
+        return;
+      }
+      // training window exhausted: shut USB3 down so the host sees a disconnect
       PFIC_DisableIRQ(USBSS_IRQn);
       PFIC_DisableIRQ(LINK_IRQn);
       usb30_hw_deinit();