Memory.v

   1 `include "ARM_Constants.v"
   2
   3 module Memory(
   4         input clk,
   5         input Nrst,
   6
   7         /* bus interface */
   8         output reg [31:0] busaddr,
   9         output reg rd_req,
  10         output reg wr_req,
  11         input rw_wait,
  12         output reg [31:0] wr_data,
  13         input [31:0] rd_data,
  14
  15         /* regfile interface */
  16         output reg [3:0] st_read,
  17         input [31:0] st_data,
  18
  19         /* Coprocessor interface */
  20         output reg cp_req,
  21         input cp_ack,
  22         input cp_busy,
  23         output cp_rnw,  /* 1 = read from CP, 0 = write to CP */
  24         input [31:0] cp_read,
  25         output reg [31:0] cp_write,
  26
  27         /* stage inputs */
  28         input inbubble,
  29         input [31:0] pc,
  30         input [31:0] insn,
  31         input [31:0] op0,
  32         input [31:0] op1,
  33         input [31:0] op2,
  34         input [31:0] spsr,
  35         input [31:0] cpsr,
  36         input write_reg,
  37         input [3:0] write_num,
  38         input [31:0] write_data,
  39
  40         /* outputs */
  41         output reg outstall,
  42         output reg outbubble,
  43         output reg [31:0] outpc,
  44         output reg [31:0] outinsn,
  45         output reg out_write_reg = 1'b0,
  46         output reg [3:0] out_write_num = 4'bxxxx,
  47         output reg [31:0] out_write_data = 32'hxxxxxxxx,
  48         output reg [31:0] out_spsr = 32'hxxxxxxxx,
  49         output reg [31:0] out_cpsr = 32'hxxxxxxxx
  50         );
  51
  52         reg [31:0] addr, raddr, prev_raddr, next_regdata, next_outcpsr;
  53         reg [3:0] next_regsel, cur_reg, prev_reg;
  54         reg next_writeback;
  55         reg [31:0] align_s1, align_s2, align_rddata;
  56
  57         wire next_outbubble;
  58         wire next_write_reg;
  59         wire [3:0] next_write_num;
  60         wire [31:0] next_write_data;
  61
  62         reg [1:0] lsr_state = 2'b01, next_lsr_state;
  63
  64         reg [15:0] regs, next_regs;
  65         reg [2:0] lsm_state = 3'b001, next_lsm_state;
  66         reg [5:0] offset, prev_offset, offset_sel;
  67
  68         reg [31:0] swp_oldval, next_swp_oldval;
  69         reg [1:0] swp_state = 2'b01, next_swp_state;
  70
  71         always @(posedge clk)
  72         begin
  73                 outpc <= pc;
  74                 outinsn <= insn;
  75                 outbubble <= next_outbubble;
  76                 out_write_reg <= next_write_reg;
  77                 out_write_num <= next_write_num;
  78                 out_write_data <= next_write_data;
  79                 regs <= next_regs;
  80                 prev_reg <= cur_reg;
  81                 prev_offset <= offset;
  82                 prev_raddr <= raddr;
  83                 out_cpsr <= next_outcpsr;
  84                 out_spsr <= spsr;
  85                 swp_state <= next_swp_state;
  86         end
  87
  88         always @(*)
  89         begin
  90                 addr = 32'hxxxxxxxx;
  91                 raddr = 32'hxxxxxxxx;
  92                 rd_req = 1'b0;
  93                 wr_req = 1'b0;
  94                 wr_data = 32'hxxxxxxxx;
  95                 busaddr = 32'hxxxxxxxx;
  96                 outstall = 1'b0;
  97                 next_write_reg = write_reg;
  98                 next_write_num = write_num;
  99                 next_write_data = write_data;
 100                 next_outbubble = inbubble;
 101                 outstall = 1'b0;
 102                 next_regs = regs;
 103                 cp_req = 1'b0;
 104                 cp_rnw = 1'bx;
 105                 cp_write = 32'hxxxxxxxx;
 106                 offset = prev_offset;
 107                 next_outcpsr = lsm_state == 3'b010 ? out_cpsr : cpsr;
 108                 next_lsm_state = lsm_state;
 109                 next_lsr_state = lsr_state;
 110                 next_swp_oldval = swp_oldval;
 111                 next_swp_state = swp_state;
 112                 cur_reg = prev_reg;
 113
 114                 /* XXX shit not given about endianness */
 115                 /* TODO ldrh/strh */
 116                 casez(insn)
 117                 `DECODE_ALU_SWP: if(!inbubble) begin
 118                         outstall = rw_wait;
 119                         next_outbubble = rw_wait;
 120                         busaddr = {op0[31:2], 2'b0};
 121                         case(swp_state)
 122                         2'b01: begin
 123                                 rd_req = 1'b1;
 124                                 outstall = 1'b1;
 125                                 if(!rw_wait) begin
 126                                         next_swp_state = 2'b10;
 127                                         next_swp_oldval = rd_data;
 128                                 end
 129                         end
 130                         2'b10: begin
 131                                 wr_req = 1'b1;
 132                                 wr_data = op1;
 133                                 next_write_reg = 1'b1;
 134                                 next_write_num = insn[15:12];
 135                                 next_write_data = swp_oldval;
 136                                 if(!rw_wait)
 137                                         next_swp_state = 2'b01;
 138                         end
 139                         default: begin end
 140                         endcase
 141                 end
 142                 `DECODE_LDRSTR_UNDEFINED: begin end
 143                 `DECODE_LDRSTR: if(!inbubble) begin
 144                         next_outbubble = rw_wait;
 145                         outstall = rw_wait;
 146                         addr = insn[23] ? op0 + op1 : op0 - op1; /* up/down select */
 147                         raddr = insn[24] ? op0 : addr; /* pre/post increment */
 148                         busaddr = {raddr[31:2], 2'b0};
 149                                 /* rotate to correct position */
 150                         align_s1 = raddr[1] ? {rd_data[15:0], rd_data[31:16]} : rd_data;
 151                         align_s2 = raddr[0] ? {align_s1[7:0], align_s1[31:8]} : align_s1;
 152                         /* select byte or word */
 153                         align_rddata = insn[22] ? {24'b0, align_s2[7:0]} : align_s2;
 154                         if(!insn[20]) begin
 155                                 wr_data = insn[22] ? {4{op2[7:0]}} : op2; /* XXX need to actually store just a byte */
 156                         end
 157                         case(lsr_state)
 158                         2'b01: begin
 159                                 rd_req = insn[20];
 160                                 wr_req = ~insn[20];
 161                                 if(insn[20]) begin
 162                                         next_write_reg = 1'b1;
 163                                         next_write_num = insn[15:12];
 164                                         next_write_data = align_rddata;
 165                                 end
 166                                         if(insn[21]) begin
 167                                         outstall = 1'b1;
 168                                         if(!rw_wait)
 169                                                 next_lsr_state = 2'b10;
 170                                 end
 171                         end
 172                         2'b10: begin
 173                                 next_write_reg = 1'b1;
 174                                 next_write_num = insn[19:16];
 175                                 next_write_data = addr;
 176                                 next_lsr_state = 2'b10;
 177                         end
 178                         default: begin end
 179                         endcase
 180                 end
 181                 /* XXX ldm/stm incorrect in that stupid case where one of the listed regs is the base reg */
 182                 `DECODE_LDMSTM: if(!inbubble) begin
 183                         outstall = rw_wait;
 184                         next_outbubble = rw_wait;
 185                         case(lsm_state)
 186                         3'b001: begin
 187 //                              next_regs = insn[23] ? op1[15:0] : op1[0:15];
 188                                 /** verilator can suck my dick */
 189                                 next_regs = insn[23] ? op1[15:0] : {op1[0], op1[1], op1[2], op1[3], op1[4], op1[5], op1[6], op1[7],
 190                                                                     op1[8], op1[9], op1[10], op1[11], op1[12], op1[13], op1[14], op1[15]};
 191                                 offset = 6'b0;
 192                                 outstall = 1'b1;
 193                                 next_lsm_state = 3'b010;
 194                         end
 195                         3'b010: begin
 196                                 rd_req = insn[20];
 197                                 wr_req = ~insn[20];
 198                                 casez(regs)
 199                                 16'b???????????????1: begin
 200                                         cur_reg = 4'h0;
 201                                         next_regs = {regs[15:1], 1'b0};
 202                                 end
 203                                 16'b??????????????10: begin
 204                                         cur_reg = 4'h1;
 205                                         next_regs = {regs[15:2], 2'b0};
 206                                 end
 207                                 16'b?????????????100: begin
 208                                         cur_reg = 4'h2;
 209                                         next_regs = {regs[15:3], 3'b0};
 210                                 end
 211                                 16'b????????????1000: begin
 212                                         cur_reg = 4'h3;
 213                                         next_regs = {regs[15:4], 4'b0};
 214                                 end
 215                                 16'b???????????10000: begin
 216                                         cur_reg = 4'h4;
 217                                         next_regs = {regs[15:5], 5'b0};
 218                                 end
 219                                 16'b??????????100000: begin
 220                                         cur_reg = 4'h5;
 221                                         next_regs = {regs[15:6], 6'b0};
 222                                 end
 223                                 16'b?????????1000000: begin
 224                                         cur_reg = 4'h6;
 225                                         next_regs = {regs[15:7], 7'b0};
 226                                 end
 227                                 16'b????????10000000: begin
 228                                         cur_reg = 4'h7;
 229                                         next_regs = {regs[15:8], 8'b0};
 230                                 end
 231                                 16'b???????100000000: begin
 232                                         cur_reg = 4'h8;
 233                                         next_regs = {regs[15:9], 9'b0};
 234                                 end
 235                                 16'b??????1000000000: begin
 236                                         cur_reg = 4'h9;
 237                                         next_regs = {regs[15:10], 10'b0};
 238                                 end
 239                                 16'b?????10000000000: begin
 240                                         cur_reg = 4'hA;
 241                                         next_regs = {regs[15:11], 11'b0};
 242                                 end
 243                                 16'b????100000000000: begin
 244                                         cur_reg = 4'hB;
 245                                         next_regs = {regs[15:12], 12'b0};
 246                                 end
 247                                 16'b???1000000000000: begin
 248                                         cur_reg = 4'hC;
 249                                         next_regs = {regs[15:13], 13'b0};
 250                                 end
 251                                 16'b??10000000000000: begin
 252                                         cur_reg = 4'hD;
 253                                         next_regs = {regs[15:14], 14'b0};
 254                                 end
 255                                 16'b?100000000000000: begin
 256                                         cur_reg = 4'hE;
 257                                         next_regs = {regs[15], 15'b0};
 258                                 end
 259                                 16'b1000000000000000: begin
 260                                         cur_reg = 4'hF;
 261                                         next_regs = 16'b0;
 262                                 end
 263                                 default: begin
 264                                         cur_reg = 4'hx;
 265                                         next_regs = 16'b0;
 266                                 end
 267                                 endcase
 268                                 cur_reg = insn[23] ? 4'hF - cur_reg : cur_reg;
 269                                 if(cur_reg == 4'hF && insn[22]) begin
 270                                         next_outcpsr = spsr;
 271                                 end
 272
 273                                 if(rw_wait) begin
 274                                         next_regs = regs;
 275                                         cur_reg = prev_reg;
 276                                         raddr = prev_raddr;
 277                                 end
 278                                 else begin
 279                                         offset = prev_offset + 6'h4;
 280                                         offset_sel = insn[24] ? offset : prev_offset;
 281                                         raddr = insn[23] ? op0 + {26'b0, offset_sel} : op0 - {26'b0, offset_sel};
 282                                         if(insn[20]) begin
 283                                                 next_write_reg = 1'b1;
 284                                                 next_write_num = cur_reg;
 285                                                 next_write_data = rd_data;
 286                                         end
 287                                 end
 288
 289                                 st_read = cur_reg;
 290                                 wr_data = st_data;
 291                                 busaddr = {raddr[31:2], 2'b0};
 292
 293                                 outstall = 1'b1;
 294
 295                                 if(next_regs == 16'b0) begin
 296                                         next_lsm_state = 3'b100;
 297                                 end
 298                         end
 299                         3'b100: begin
 300                                 next_write_reg = 1'b1;
 301                                 next_write_num = insn[19:16];
 302                                 next_write_data = insn[23] ? op0 + {26'b0, prev_offset} : op0 - {26'b0, prev_offset};
 303                                 next_lsm_state = 3'b001;
 304                         end
 305                         default: begin end
 306                         endcase
 307                 end
 308                 `DECODE_LDCSTC: if(!inbubble) begin
 309                         $display("WARNING: Unimplemented LDCSTC");
 310                 end
 311                 `DECODE_CDP: if(!inbubble) begin
 312                         cp_req = 1;
 313                         if (cp_busy) begin
 314                                 outstall = 1;
 315                                 next_outbubble = 1;
 316                         end
 317                         if (!cp_ack) begin
 318                                 /* XXX undefined instruction trap */
 319                                 $display("WARNING: Possible CDP undefined instruction");
 320                         end
 321                 end
 322                 `DECODE_MRCMCR: if(!inbubble) begin
 323                         cp_req = 1;
 324                         cp_rnw = insn[20] /* L */;
 325                         if (insn[20] == 0 /* store to coprocessor */)
 326                                 cp_write = op0;
 327                         else begin
 328                                 if (insn[15:12] != 4'hF /* Fuck you ARM */) begin
 329                                         next_write_reg = 1'b1;
 330                                         next_write_num = insn[15:12];
 331                                         next_write_data = cp_read;
 332                                 end else
 333                                         next_outcpsr = {cp_read[31:28], cpsr[27:0]};
 334                         end
 335                         if (cp_busy) begin
 336                                 outstall = 1;
 337                                 next_outbubble = 1;
 338                         end
 339                         if (!cp_ack) begin
 340                                 $display("WARNING: Possible MRCMCR undefined instruction");
 341                         end
 342                 end
 343                 default: begin end
 344                 endcase
 345         end
 346 endmodule