riscv single cycle cpu with separate IMEM and DMEM working

Author: JulianKemmerer

examples/risc-v/gcc_test/Makefile

@@ -16,8 +16,12 @@ dump-comment: all
 	objdump -s --section .comment main
 
 hex: all
-	./elf2bin.py main mem_init.h
-    
+	#./elf2bin.py main mem_init.h
+	riscv32-unknown-elf-objcopy -O binary main text.bin --only-section .text
+	./bin2vhdl.py text.bin
+	riscv32-unknown-elf-objcopy -O binary main data.bin --only-section .data
+	./bin2vhdl.py data.bin
+	
 clean:
 	rm -f main
 

examples/risc-v/gcc_test/bin2vhdl.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+
+# Parse .bin files output from commands like
+#   riscv32-unknown-elf-objcopy -O binary main text.bin --only-section .text
+# into VHDL array of u32 init string
+
+import sys
+import struct
+
+# VHDL doesnt accept DECIMAL 32b unsigned value constants
+# since sees as signed 33b integer w/sign bit=0
+# so instead explictly convert 32b unsigned to 32b signed
+# Thanks https://stackoverflow.com/questions/24563786/conversion-from-hex-to-signed-dec-in-python
+def s32(value):
+    return -(value & 0x80000000) | (value & 0x7fffffff)
+
+in_file = sys.argv[1]
+
+fin = open(in_file, "rb")
+name = in_file.strip(".bin")
+
+four_bytes = fin.read(4)
+word_count = 0
+s = f'#define {name}_MEM_INIT "(\\n\\\n'
+while len(four_bytes)==4:
+  word_count += 1
+  LITTLE_END_INTEGER = '<i'
+  the_int = struct.unpack(LITTLE_END_INTEGER, four_bytes)[0]
+  word_str = f"unsigned(to_signed({str(s32(the_int))}, 32))"
+  word_str += ",\\n\\\n"
+  s += word_str
+  four_bytes = fin.read(4)
+
+s += "others => (others => '0')\\n\\\n"
+s += ')"\n'
+#s += f'#define MEM_INIT_SIZE {word_count*4}\n'
+with open(name+"_mem_init.h", "w") as of:
+  of.write(s)
+

examples/risc-v/gcc_test/bootstrap.S

@@ -1,5 +1,4 @@
-# It does not appear possible to specify
-# bootstrap assembly directly in asm("...") C code.
+# It require some work to do bootstrap for C code it seems...
 # For that reason setup that occurs 
 # before the C code entry point is done here
 
@@ -12,10 +11,4 @@
 # And then start user main()
 _bootstrap:
 la sp, stack_end
-jal main
-
-# Declare a stack area of memory? 
-# (must be after entry point? or last in order?)
-stack_begin:
-.zero 256
-stack_end:
+jal main

examples/risc-v/gcc_test/link.ld

@@ -4,11 +4,49 @@ https://github.com/agra-uni-bremen/microrv32/blob/master/microrv32/sw/basic-c/li
 OUTPUT_ARCH( "riscv" )
 ENTRY(_bootstrap)
 
-SECTIONS
+/* and Discord user dutracgi,
+https://interrupt.memfault.com/blog/how-to-write-linker-scripts-for-firmware */
+
+/* Needs to match mem_map.h (TODO how to share variables?) */
+MEMORY
 {
-  /* Place entry point at address 0*/
-  . = 0;
-  .text.init : { *(.text.init) }
+  rom      (rx) : ORIGIN = 0x00000000, LENGTH = 65536
+  ram      (rw) : ORIGIN = 0x40000000, LENGTH = 65536
 }
 
+STACK_SIZE = 0x0100;
+
+/* Section Definitions */
+SECTIONS
+{
+    .text :
+    {
+        KEEP(*(.vectors .vectors.*))
+        *(.text*)
+        *(.rodata*)
+    } > rom
 
+    /* .bss section which is used for uninitialized data */
+    .bss (NOLOAD) :
+    {
+        *(.bss*)
+        *(COMMON)
+    } > ram
+
+    .data :
+    {
+        *(.data*);
+    } > ram AT >rom
+
+    /* stack section */
+    .stack (NOLOAD):
+    {
+        . = ALIGN(4);
+        stack_begin = .; /* stack base is here */
+        . = . + STACK_SIZE;
+        . = ALIGN(4);
+        stack_end = .; /* stack top is here <- sp */
+    } > ram
+
+    _end = . ;
+}

examples/risc-v/gcc_test/mem_map.h

@@ -19,7 +19,14 @@
 // TODO just mem map one big struct that gets changes
 //  needs more efficient code for muxing mem reads/writes to specific struct bytes
 
-#define MEM_MAP_BASE_ADDR 0x10000000
+// Needs to match link.ld (TODO how to share variables?)
+#define DMEM_ADDR_BIT_CHECK 30
+#define DMEM_BASE_ADDR ((uint32_t)((uint32_t)1<<DMEM_ADDR_BIT_CHECK))
+#define DMEM_SIZE 65536 // Must be decimal constant since VHDL+C literal
+#define IMEM_SIZE 65536 // Must be decimal constant since VHDL+C literal
+// Any addresses this high up will be mmio
+#define MEM_MAP_ADDR_BIT_CHECK 31
+#define MEM_MAP_BASE_ADDR ((uint32_t)((uint32_t)1<<MEM_MAP_ADDR_BIT_CHECK))
 
 #define N_THREADS_PER_BARREL 5
 #define N_BARRELS 1
@@ -467,7 +474,7 @@ typedef struct dataflow_mm_t
 #define DATAFLOW_MM_ADDR (KERNEL_VALID_OUT_ADDR + sizeof(uint32_t))
 static volatile dataflow_mm_t* DATAFLOW_MM = (dataflow_mm_t*)DATAFLOW_MM_ADDR;
 
-void do_shader_dataflow(uint32_t addr, int32_t x, int32_t y, uint32_t frame_count, uint32_t num_pixels){
+/*void do_shader_dataflow(uint32_t addr, int32_t x, int32_t y, uint32_t frame_count, uint32_t num_pixels){
   // Configure dataflow network
   DATAFLOW_MM->addr = addr;
   DATAFLOW_MM->x = x;
@@ -482,4 +489,4 @@ void do_shader_dataflow(uint32_t addr, int32_t x, int32_t y, uint32_t frame_coun
   // Clear valid to reset
   DATAFLOW_MM->all_ports_dataflow_host = 0;
   DATAFLOW_MM->valid = 0;
-}
+}*/