usb gets fast

fw/rtl/cpu/cpu_usb.sv

@@ -28,6 +28,7 @@ module cpu_usb (
     logic cpu_tx_write;
 
     logic usb_enabled;
+    logic tx_force;
 
     always_comb begin
         dma.rx_empty = rx_empty;
@@ -66,6 +67,7 @@ module cpu_usb (
         cpu_tx_write <= 1'b0;
 
         rx_escape_ack <= 1'b0;
+        tx_force <= 1'b0;
 
         if (sys.reset) begin
             usb_enabled <= 1'b0;
@@ -73,6 +75,9 @@ module cpu_usb (
             if (bus.request) begin
                 case (bus.address[2:2])
                     2'd0: begin
+                        if (bus.wmask[1]) begin
+                            tx_force <= bus.wdata[8];
+                        end
                         if (bus.wmask[0]) begin
                             rx_escape_ack <= bus.wdata[7];
                             {usb_enabled, tx_flush, rx_flush} <= bus.wdata[4:2];
@@ -95,6 +100,7 @@ module cpu_usb (
         .sys(sys),
 
         .usb_enabled(usb_enabled),
+        .tx_force(tx_force),
 
         .usb_clk(usb_clk),
         .usb_cs(usb_cs),

fw/rtl/usb/usb_ft1248.sv

@@ -2,6 +2,7 @@ module usb_ft1248 (
     if_system.sys sys,
 
     input usb_enabled,
+    input tx_force,
 
     output usb_clk,
     output usb_cs,
@@ -111,7 +112,8 @@ module usb_ft1248 (
 
     typedef enum bit [7:0] {
         C_WRITE = 8'h00,
-        C_READ = 8'h04
+        C_READ = 8'h04,
+        C_FORCE = 8'h80
     } e_command;
 
     typedef enum bit [1:0] {
@@ -134,7 +136,9 @@ module usb_ft1248 (
     logic usb_miosi_output_enable_data;
     logic usb_miso_input;
 
+    logic tx_force_pending;
     logic is_cmd_write;
+    logic is_cmd_tx_force;
     logic [1:0] nibble_counter;
     logic [7:0] tx_buffer;
 
@@ -168,7 +172,9 @@ module usb_ft1248 (
             S_COMMAND: begin
                 usb_clk_output = clock_phase[P_PRE_FALLING] || clock_phase[P_FALLING];
                 usb_cs_output = 1'b0;
-                if (is_cmd_write) begin
+                if (is_cmd_tx_force) begin
+                    usb_miosi_output_data = nibble_counter[0] ? C_FORCE[3:0] : C_FORCE[7:4];
+                end else if (is_cmd_write) begin
                     usb_miosi_output_data = nibble_counter[0] ? C_WRITE[3:0] : C_WRITE[7:4];
                 end else begin
                     usb_miosi_output_data = nibble_counter[0] ? C_READ[3:0] : C_READ[7:4];
@@ -202,12 +208,18 @@ module usb_ft1248 (
 
         if (sys.reset || !usb_enabled) begin
             state <= S_TRY_RX;
+            tx_force_pending <= 1'b0;
         end else begin
+            if (tx_force) begin
+                tx_force_pending <= 1'b1;
+            end
+
             case (state)
                 S_TRY_RX: begin
                     if (!rx_full && !rx_escape_valid) begin
                         state <= S_COMMAND;
                         is_cmd_write <= 1'b0;
+                        is_cmd_tx_force <= 1'b0;
                         nibble_counter <= 2'b11;
                     end else begin
                         state <= S_TRY_TX;
@@ -218,6 +230,13 @@ module usb_ft1248 (
                     if (!tx_empty) begin
                         state <= S_COMMAND;
                         is_cmd_write <= 1'b1;
+                        is_cmd_tx_force <= 1'b0;
+                        nibble_counter <= 2'b11;
+                    end else if (tx_force_pending) begin
+                        state <= S_COMMAND;
+                        tx_force_pending <= 1'b0;
+                        is_cmd_write <= 1'b1;
+                        is_cmd_tx_force <= 1'b1;
                         nibble_counter <= 2'b11;
                     end else begin
                         state <= S_TRY_RX;
@@ -227,7 +246,7 @@ module usb_ft1248 (
                 S_COMMAND: begin
                     if (clock_phase[P_RISING]) begin
                         if (nibble_counter == 2'd2) begin
-                            if (usb_miso_input) begin
+                            if (usb_miso_input || is_cmd_tx_force) begin
                                 state <= is_cmd_write ? S_TRY_RX : S_TRY_TX;
                             end else begin
                                 state <= S_DATA;

sw/n64/src/exception.S

@@ -1,7 +1,7 @@
 #include "vr4300.h"
 
 
-#define WATCHDOG_TIMEOUT            (1 * (93750000UL / 2))
+#define WATCHDOG_TIMEOUT            (5 * (93750000UL / 2))
 
 #define VECTOR_LOCATION             (0xA0000000UL)
 #define VECTOR_SIZE                 (0x80)

sw/n64/src/exception.c

@@ -276,7 +276,7 @@ void exception_fatal_handler (uint32_t exception_code, uint32_t interrupt_mask,
     if (exception_code == EXCEPTION_INTERRUPT) {
         if (interrupt_mask & INTERRUPT_MASK_TIMER) {
             exception_disable_watchdog();
-            exception_print("Still loading after 1 second limit...\n\n");
+            exception_print("Still loading after 5 second limit...\n\n");
             return;
         }
     } else if (exception_code == EXCEPTION_SYSCALL) {

sw/riscv/src/sys.h

@@ -105,6 +105,7 @@ typedef volatile struct usb_regs {
 #define USB_SCR_PWREN               (1 << 5)
 #define USB_SCR_ESCAPE_PENDING      (1 << 6)
 #define USB_SCR_ESCAPE_ACK          (1 << 7)
+#define USB_SCR_FORCE_TX            (1 << 8)
 
 
 typedef volatile struct uart_regs {

sw/riscv/src/usb.c

@@ -252,6 +252,9 @@ void process_usb (void) {
                                     }
                                 }
                                 p.state = STATE_IDLE;
+                                if (p.cmd == 'L') {
+                                    USB->SCR |= USB_SCR_FORCE_TX;
+                                }
                             } else {
                                 p.state = STATE_RESPONSE;
                             }
@@ -303,6 +306,7 @@ void process_usb (void) {
         case STATE_RESPONSE:
             if (tx_word((p.error ? USB_ERR_TOKEN : USB_CMP_TOKEN) | p.cmd)) {
                 p.state = STATE_IDLE;
+                USB->SCR |= USB_SCR_FORCE_TX;
             }
             break;
 
@@ -327,6 +331,7 @@ void process_usb (void) {
                 }
                 p.event_pending = false;
                 p.state = STATE_IDLE;
+                USB->SCR |= USB_SCR_FORCE_TX;
             }
             break;
     }