software/bios: add new mem_list command to list available memory regi…

…ons.

This is useful to know the memory regions available and use the mem_xy commands
on them:

List the memory regions:

litex> mem_list
Available memory regions:
ROM       0x00000000 0x8000
SRAM      0x01000000 0x2000
MAIN_RAM  0x40000000 0x10000000
CSR       0x82000000 0x10000

Test 0x1000 bytes of MAIN_RAM:

litex> mem_test 0x40000000 0x1000
Memtest at 0x40000000 (4KiB)...
  Write: 0x40000000-0x40001000 4KiB
   Read: 0x40000000-0x40001000 4KiB
Memtest OK

Test speed on 0x1000 bytes of MAIN_RAM:

litex> mem_speed 0x40000000 0x1000
Memspeed at 0x40000000 (4KiB)...
  Write speed: 352KiB/s
   Read speed: 288KiB/s

litex/soc/integration/export.py

@@ -121,16 +121,27 @@ def get_mem_header(regions):
     r = generated_banner("//")
     r += "#ifndef __GENERATED_MEM_H\n#define __GENERATED_MEM_H\n\n"
     for name, region in regions.items():
-        r += "#ifndef {name}\n".format(name=name.upper())
-        r += "#define {name}_BASE 0x{base:08x}L\n#define {name}_SIZE 0x{size:08x}\n\n".format(
+        r += "#ifndef {name}_BASE\n".format(name=name.upper())
+        r += "#define {name}_BASE 0x{base:08x}L\n#define {name}_SIZE 0x{size:08x}\n".format(
             name=name.upper(), base=region.origin, size=region.length)
-        r += "#endif\n"
+        r += "#endif\n\n"
+
+    r += "#ifndef MEM_REGIONS\n"
+    r += "#define MEM_REGIONS \"";
+    for name, region in regions.items():
+        r += f"{name.upper()} {' '*(8-len(name))} 0x{region.origin:08x} 0x{region.size:x} \\n"
+    r = r[:-2]
+    r += "\"\n"
+    r += "#endif\n"
+
     r += "#endif\n"
     return r
 
 def get_soc_header(constants, with_access_functions=True):
     r = generated_banner("//")
     r += "#ifndef __GENERATED_SOC_H\n#define __GENERATED_SOC_H\n"
+
+
     for name, value in constants.items():
         if value is None:
             r += "#define "+name+"\n"

litex/soc/software/bios/cmds/cmd_mem.c

@@ -5,10 +5,25 @@
 #include <memtest.h>
 
 #include <generated/csr.h>
+#include <generated/mem.h>
 
 #include "../command.h"
 #include "../helpers.h"
 
+/**
+ * Command "mem_list"
+ *
+ * Memory list
+ *
+ */
+static void mem_list_handler(int nb_params, char **params)
+{
+	printf("Available memory regions:\n");
+	puts(MEM_REGIONS);
+}
+
+define_command(mem_list, mem_list_handler, "List available memory regions", MEM_CMDS);
+
 /**
  * Command "mem_read"
  *