blegh.

* add in a new PRE_IDLE state into issue FSM (to allow pc_at_reset to
  get a word in edgeways)
* set nia to pc_at_reset on core_rst (not 0x0)
* add in a terrible hack where the STATE regfile entry for PC is
  shifted down by one.

absolutely no frickin idea why that is needed

diff --git a/Makefile b/Makefile
index 736cd7b1ac2ace8e379e6a941d3e1f0adaf4c0de..8d379590387090fa04a28b2b64ebac56c26231ec 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -72,7 +72,7 @@ microwatt_external_core_spi:
 microwatt_external_core_bram:
        python3 src/soc/simple/issuer_verilog.py --microwatt-compat \
             --enable-mmu \
-            --pc-reset 0xFFF00000 \
+            --pc-reset 0xFF000000 \
             external_core_top.v
 
 # build the litex libresoc SoC without 4k SRAMs

diff --git a/src/soc/simple/core.py b/src/soc/simple/core.py
index 9a4abacc3135e647ae4be3d9a8b7882e7ce68fe4..10fe1f864b970b2be32bdc400bca591aed8c0765 100644 (file)
--- a/src/soc/simple/core.py
+++ b/src/soc/simple/core.py
@@ -168,7 +168,7 @@ class NonProductionCore(ControlBase):
             self.msr_at_reset = pspec.msr_reset
         if hasattr(pspec, "pc_reset") and isinstance(pspec.pc_reset, int):
             self.pc_at_reset = pspec.pc_reset
-        state_resets = [self.pc_at_reset,  # PC at reset
+        state_resets = [self.pc_at_reset>>1,  # PC at reset
                         self.msr_at_reset, # MSR at reset
                         0x0,               # SVSTATE at reset
                         0x0,               # DEC at reset

diff --git a/src/soc/simple/issuer.py b/src/soc/simple/issuer.py
index a80941dbd26e01ff6cc014cb1fab1531ff509fda..7ea8ff330b8017d21d80744ea366efb8c503590d 100644 (file)
--- a/src/soc/simple/issuer.py
+++ b/src/soc/simple/issuer.py
@@ -626,6 +626,7 @@ class TestIssuerBase(Elaboratable):
         with m.If(core_rst):
             m.d.sync += self.cur_state.eq(0)
             # and, sigh, set configured values, which are also done in regfile
+            # XXX ??? what the hell is the shift for??
             m.d.sync += self.cur_state.pc.eq(self.core.pc_at_reset)
             m.d.sync += self.cur_state.msr.eq(self.core.msr_at_reset)
 
@@ -805,7 +806,7 @@ class TestIssuerInternal(TestIssuerBase):
     easy understanding) come later.
     """
 
-    def fetch_fsm(self, m, dbg, core, nia, is_svp64_mode,
+    def fetch_fsm(self, m, dbg, core, core_rst, nia, is_svp64_mode,
                         fetch_pc_o_ready, fetch_pc_i_valid,
                         fetch_insn_o_valid, fetch_insn_i_ready):
         """fetch FSM
@@ -839,7 +840,7 @@ class TestIssuerInternal(TestIssuerBase):
             # allow fetch to not run at startup due to I-Cache reset not
             # having time to settle.  power-on-reset holds dbg.core_stopped_i
             with m.State("PRE_IDLE"):
-                with m.If(~dbg.core_stopped_i & ~dbg.core_stop_o):
+                with m.If(~dbg.core_stopped_i & ~dbg.core_stop_o & ~core_rst):
                     m.next = "IDLE"
 
             # waiting (zzz)
@@ -1188,6 +1189,10 @@ class TestIssuerInternal(TestIssuerBase):
 
         with m.FSM(name="issue_fsm"):
 
+            with m.State("PRE_IDLE"):
+                with m.If(~dbg.core_stop_o & ~core_rst):
+                    m.next = "ISSUE_START"
+
             # sync with the "fetch" phase which is reading the instruction
             # at this point, there is no instruction running, that
             # could inadvertently update the PC.
@@ -1597,7 +1602,7 @@ class TestIssuerInternal(TestIssuerBase):
         # Issue is where the VL for-loop # lives.  the ready/valid
         # signalling is used to communicate between the four.
 
-        self.fetch_fsm(m, dbg, core, nia, is_svp64_mode,
+        self.fetch_fsm(m, dbg, core, core_rst, nia, is_svp64_mode,
                        fetch_pc_o_ready, fetch_pc_i_valid,
                        fetch_insn_o_valid, fetch_insn_i_ready)
 
@@ -1619,9 +1624,10 @@ class TestIssuerInternal(TestIssuerBase):
                          exec_insn_i_valid, exec_insn_o_ready,
                          exec_pc_o_valid, exec_pc_i_ready)
 
-        # whatever was done above, over-ride it if core reset is held
+        # whatever was done above, over-ride it if core reset is held.
+        # set NIA to pc_at_reset
         with m.If(core_rst):
-            sync += nia.eq(0)
+            sync += nia.eq(self.core.pc_at_reset)
 
         return m