cpu/vexriscv_smp: Set UART/Timer0 CSRs as done on NaxRiscv to ensure OpenSBI compatibility.

This also allow generating bitstreams for Linux-on-LiteX-VexRiscv directly from litex-boards.

litex/soc/cores/cpu/naxriscv/core.py

@@ -254,6 +254,7 @@ class NaxRiscv(CPU):
         platform.add_source(os.path.join(vdir,  self.netlist_name + ".v"), "verilog")
 
     def add_soc_components(self, soc, soc_region_cls):
+        # Set UART/Timer0 CSRs to the ones used by OpenSBI.
         soc.csr.add("uart",   n=2)
         soc.csr.add("timer0", n=3)
 

litex/soc/cores/cpu/vexriscv_smp/core.py

@@ -375,6 +375,10 @@ class VexRiscvSMP(CPU):
         platform.add_source(os.path.join(vdir,  self.cluster_name + ".v"), "verilog")
 
     def add_soc_components(self, soc, soc_region_cls):
+        # Set UART/Timer0 CSRs to the ones used by OpenSBI.
+        soc.csr.add("uart",   n=2)
+        soc.csr.add("timer0", n=3)
+
         # Define number of CPUs
         soc.add_config("CPU_COUNT", VexRiscvSMP.cpu_count)
         soc.add_constant("CPU_ISA", VexRiscvSMP.get_arch())