fpga: Only allow system reset in firmware mode and syscalls

hw/application_fpga/core/tk1/rtl/tk1.v

@@ -547,7 +547,9 @@ module tk1 #(
         end
 
         if (address == ADDR_SYSTEM_RESET) begin
-          system_reset_new = 1'h1;
+          if (!app_mode) begin
+            system_reset_new = 1'h1;
+          end
         end
 
         if ((address >= ADDR_CDI_FIRST) && (address <= ADDR_CDI_LAST)) begin

hw/application_fpga/core/tk1/tb/tb_tk1.v

@@ -56,6 +56,8 @@ module tb_tk1 ();
   localparam ADDR_CPU_MON_FIRST = 8'h61;
   localparam ADDR_CPU_MON_LAST = 8'h62;
 
+  localparam ADDR_SYSTEM_RESET = 8'h70;
+
   localparam ADDR_SPI_EN = 8'h80;
   localparam ADDR_SPI_XFER = 8'h81;
   localparam ADDR_SPI_DATA = 8'h82;
@@ -84,6 +86,7 @@ module tb_tk1 ();
   reg           tb_cpu_instr;
   reg           tb_cpu_valid;
   wire          tb_force_trap;
+  wire          tb_system_reset;
 
   wire [14 : 0] tb_ram_addr_rand;
   wire [31 : 0] tb_ram_data_rand;
@@ -132,6 +135,7 @@ module tb_tk1 ();
       .cpu_instr (tb_cpu_instr),
       .cpu_valid (tb_cpu_valid),
       .force_trap(tb_force_trap),
+      .system_reset(tb_system_reset),
 
       .ram_addr_rand(tb_ram_addr_rand),
       .ram_data_rand(tb_ram_data_rand),
@@ -1120,6 +1124,45 @@ module tb_tk1 ();
   endtask  // test12
 
 
+  //----------------------------------------------------------------
+  // test13()
+  // System reset
+  //----------------------------------------------------------------
+  task test13;
+    begin
+      tc_ctr = tc_ctr + 1;
+
+      $display("");
+      $display("--- test13: Reset allowed from firmware mode.");
+      tb_syscall = 0;
+      reset_dut();
+
+      write_word(ADDR_SYSTEM_RESET, 32'h1);
+      check_equal(tb_system_reset, 1);
+
+      $display("--- test13: Reset not allowed from app mode.");
+      reset_dut();
+      fetch_instruction(APP_RAM_START);
+
+      write_word(ADDR_SYSTEM_RESET, 32'h1);
+      check_equal(tb_system_reset, 0);
+
+      $display("--- test13: Reset allowed from syscall.");
+      reset_dut();
+      fetch_instruction(APP_RAM_START);
+      tb_syscall = 1;
+
+      write_word(ADDR_SYSTEM_RESET, 32'h1);
+      check_equal(tb_system_reset, 1);
+
+      tb_syscall = 0;
+
+      $display("--- test13: completed.");
+      $display("");
+    end
+  endtask  // test13
+
+
   //----------------------------------------------------------------
   // exit_with_error_code()
   //
@@ -1161,6 +1204,7 @@ module tb_tk1 ();
     test10();
     test11();
     test12();
+    test13();
 
     display_test_result();
     $display("");

hw/application_fpga/fw/testapp/main.c

@@ -20,6 +20,7 @@ volatile uint32_t *uds              = (volatile uint32_t *)TK1_MMIO_UDS_FIRST;
 volatile uint32_t *cdi              = (volatile uint32_t *)TK1_MMIO_TK1_CDI_FIRST;
 volatile uint32_t *udi              = (volatile uint32_t *)TK1_MMIO_TK1_UDI_FIRST;
 volatile uint8_t  *fw_ram           = (volatile uint8_t  *)TK1_MMIO_FW_RAM_BASE;
+volatile uint32_t *system_reset     = (volatile uint32_t *)TK1_MMIO_TK1_SYSTEM_RESET;
 volatile uint32_t *timer            = (volatile uint32_t *)TK1_MMIO_TIMER_TIMER;
 volatile uint32_t *timer_prescaler  = (volatile uint32_t *)TK1_MMIO_TIMER_PRESCALER;
 volatile uint32_t *timer_status     = (volatile uint32_t *)TK1_MMIO_TIMER_STATUS;
@@ -192,6 +193,11 @@ int main(void)
 		anyfailed = 1;
 	}
 
+	// Should NOT be able to reset Tkey from app mode
+	puts("\r\nTesting system reset...");
+	*system_reset = 1;
+	puts("done.\r\n");
+
 	// Test FW_RAM.
 	*fw_ram = 0x21;
 	if (*fw_ram == 0x21) {

hw/application_fpga/fw/testfw/main.c

@@ -17,6 +17,7 @@ volatile uint32_t *uds              = (volatile uint32_t *)TK1_MMIO_UDS_FIRST;
 volatile uint32_t *cdi              = (volatile uint32_t *)TK1_MMIO_TK1_CDI_FIRST;
 volatile uint32_t *udi              = (volatile uint32_t *)TK1_MMIO_TK1_UDI_FIRST;
 volatile uint8_t  *fw_ram           = (volatile uint8_t  *)TK1_MMIO_FW_RAM_BASE;
+volatile uint32_t *system_reset     = (volatile uint32_t *)TK1_MMIO_TK1_SYSTEM_RESET;
 volatile uint32_t *timer            = (volatile uint32_t *)TK1_MMIO_TIMER_TIMER;
 volatile uint32_t *timer_prescaler  = (volatile uint32_t *)TK1_MMIO_TIMER_PRESCALER;
 volatile uint32_t *timer_status     = (volatile uint32_t *)TK1_MMIO_TIMER_STATUS;
@@ -355,9 +356,12 @@ int main(void)
 	}
 	puts("\r\n");
 
-	puts("Now echoing what you type...\r\n");
+	puts("Now echoing what you type...Type + to reset device\r\n");
 	for (;;) {
 		in = readbyte(&mode, &mode_bytes_left);
+		if (in == '+') {
+			*system_reset = 1;
+		}
 
 		writebyte(MODE_CDC);
 		writebyte(1);