FPGA: Add system reset API

Add API address to trigger system reset.
      When written to will send system_reset signal
      to the reset generator, which then perform a complete
      reset cycle of the FPGA system.

Signed-off-by: Joachim Strömbergson <joachim@assured.se>

hw/application_fpga/application_fpga.bin.sha256

@@ -1 +1 @@
-c6105a3f769c0846a9619e194ed3bc171467612b9fef9edc1aaeda4941316ff5  application_fpga.bin
+24e642b0dc78a7dbf4cd87c223dd26eefb1ad444c96858e1c2b373f35701ccc0  application_fpga.bin

hw/application_fpga/core/tk1/README.md

@@ -248,6 +248,32 @@ see the datasheet:
 https://www.mouser.se/datasheet/2/949/w25q80dv_dl_revh_10022015-1489677.pdf
 
 
+## System Reset
+
+The TK1 includes an ability for FW and applications to trigger a
+hardware reset of the FPGA by writing to an API address.
+
+The hardware reset will force all registers that are in the Tkey FPGA
+design reset circuit to be reset to their default values. Basically
+this is all registers in the Tkey FPGA design.
+
+The reset will not clear the RAM. However since the CPU program
+counter is reset to its reset vector, the CPU will unconditionally
+start executing the FW. As part of the device initialization, the FW
+will fill the RAM with random data, overwriting any app and
+data present in the RAM before the reset was triggered.
+
+The hardware reset will not force the FPGA to read its
+configuration. That requires a power cycle of the Tkey device.
+
+The reset is controlled by the following API address. Note that
+any value written to the address will trigger the reset.
+
+```
+localparam ADDR_SYSTEM_RESET  = 8'h70;
+```
+
+
 ## Implementation
 
 The core is implemented as a single module. Future versions will

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

@@ -24,6 +24,7 @@ module tk1(
 	   input wire           cpu_instr,
 	   input wire           cpu_valid,
 	   output wire          force_trap,
+	   output               system_reset,
 
 	   output wire [14 : 0] ram_addr_rand,
 	   output wire [31 : 0] ram_data_rand,
@@ -93,6 +94,8 @@ module tk1(
   localparam ADDR_CPU_MON_FIRST = 8'h61;
   localparam ADDR_CPU_MON_LAST  = 8'h62;
 
+  localparam ADDR_SYSTEM_RESET  = 8'h70;
+
 `ifdef INCLUDE_SPI_MASTER
   localparam ADDR_SPI_EN        = 8'h80;
   localparam ADDR_SPI_XFER      = 8'h81;
@@ -146,6 +149,9 @@ module tk1(
   reg [31 : 0] ram_data_rand_reg;
   reg          ram_data_rand_we;
 
+  reg          system_reset_reg;
+  reg          system_reset_new;
+
   reg          cpu_mon_en_reg;
   reg          cpu_mon_en_we;
   reg [31 : 0] cpu_mon_first_reg;
@@ -196,6 +202,8 @@ module tk1(
   assign ram_addr_rand = ram_addr_rand_reg;
   assign ram_data_rand = ram_data_rand_reg;
 
+  assign system_reset = system_reset_reg;
+
 
   //----------------------------------------------------------------
   // Module instance.
@@ -276,11 +284,14 @@ module tk1(
  	ram_addr_rand_reg <= 15'h0;
 	ram_data_rand_reg <= 32'h0;
 	force_trap_reg    <= 1'h0;
+	system_reset_reg  <= 1'h0;
       end
 
       else begin
 	cpu_trap_ctr_reg <= cpu_trap_ctr_new;
 
+	system_reset_reg <= system_reset_new;
+
         gpio1_reg[0] <= gpio1;
         gpio1_reg[1] <= gpio1_reg[0];
 
@@ -429,6 +440,7 @@ module tk1(
       cdi_mem_we       = 1'h0;
       ram_addr_rand_we = 1'h0;
       ram_data_rand_we = 1'h0;
+      system_reset_new = 1'h0;
       cpu_mon_en_we    = 1'h0;
       cpu_mon_first_we = 1'h0;
       cpu_mon_last_we  = 1'h0;
@@ -473,6 +485,10 @@ module tk1(
             end
 	  end
 
+          if (address == ADDR_SYSTEM_RESET) begin
+            system_reset_new = 1'h1;
+          end
+
           if (address == ADDR_BLAKE2S) begin
 	    if (!switch_app_reg) begin
               blake2s_addr_we = 1'h1;

hw/application_fpga/fw/tk1_mem.h

@@ -144,6 +144,8 @@
 #define TK1_MMIO_TK1_CPU_MON_FIRST 0xff000184
 #define TK1_MMIO_TK1_CPU_MON_LAST 0xff000188
 
+#define TK1_MMIO_TK1_SYSTEM_RESET 0xff0001C0
+
 #define TK1_MMIO_TK1_SPI_EN 0xff000200
 #define TK1_MMIO_TK1_SPI_XFER 0xff000204
 #define TK1_MMIO_TK1_SPI_DATA 0xff000208

hw/application_fpga/rtl/application_fpga.v

@@ -148,6 +148,7 @@ module application_fpga(
   wire          force_trap;
   wire [14 : 0] ram_addr_rand;
   wire [31 : 0] ram_data_rand;
+  wire          tk1_system_reset;
   /* verilator lint_on UNOPTFLAT */
 
 
@@ -155,7 +156,11 @@ module application_fpga(
   // Module instantiations.
   //----------------------------------------------------------------
   clk_reset_gen #(.RESET_CYCLES(200))
-  reset_gen_inst(.clk(clk), .rst_n(reset_n));
+  reset_gen_inst(
+		 .sys_reset(tk1_system_reset),
+		 .clk(clk),
+		 .rst_n(reset_n)
+		);
 
 
   picorv32 #(
@@ -321,6 +326,8 @@ module application_fpga(
 	       .cpu_trap(cpu_trap),
 	       .force_trap(force_trap),
 
+	       .system_reset(tk1_system_reset),
+
                .ram_addr_rand(ram_addr_rand),
 	       .ram_data_rand(ram_data_rand),
 

hw/application_fpga/rtl/clk_reset_gen.v

@@ -18,6 +18,8 @@
 
 module clk_reset_gen #(parameter RESET_CYCLES = 200)
   (
+   input wire sys_reset,
+
    output wire clk,
    output wire rst_n
    );
@@ -33,6 +35,12 @@ module clk_reset_gen #(parameter RESET_CYCLES = 200)
   reg         rst_n_reg = 1'h0;
   reg         rst_n_new;
 
+  reg         sys_reset_reg;
+
+
+  //----------------------------------------------------------------
+  // Wires.
+  //----------------------------------------------------------------
   wire        hfosc_clk;
   wire        pll_clk;
 
@@ -93,7 +101,8 @@ module clk_reset_gen #(parameter RESET_CYCLES = 200)
   //----------------------------------------------------------------
     always @(posedge clk)
       begin : reg_update
-        rst_n_reg <= rst_n_new;
+        rst_n_reg     <= rst_n_new;
+	sys_reset_reg <= sys_reset;
 
         if (rst_ctr_we)
           rst_ctr_reg <= rst_ctr_new;
@@ -109,7 +118,12 @@ module clk_reset_gen #(parameter RESET_CYCLES = 200)
       rst_ctr_new = 8'h0;
       rst_ctr_we  = 1'h0;
 
-      if (rst_ctr_reg < RESET_CYCLES) begin
+      if (sys_reset_reg) begin
+	rst_ctr_new = 8'h0;
+	rst_ctr_we  = 1'h1;
+      end
+
+      else if (rst_ctr_reg < RESET_CYCLES) begin
         rst_n_new   = 1'h0;
         rst_ctr_new = rst_ctr_reg + 1'h1;
         rst_ctr_we  = 1'h1;