From c61699f9b9a02b4db587151471616638d7388fc3 Mon Sep 17 00:00:00 2001
From: Daniel Benusovich <flyingmonkeys1996@gmail.com>
Date: Sat, 20 Apr 2019 18:06:34 -0700
Subject: [PATCH] Add tlb_content with TLBContent and TLBEntry classes

---
 TLB/src/ariane/tlb_content.py | 125 ++++++++++++++++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 TLB/src/ariane/tlb_content.py

diff --git a/TLB/src/ariane/tlb_content.py b/TLB/src/ariane/tlb_content.py
new file mode 100644
index 00000000..8464ac80
--- /dev/null
+++ b/TLB/src/ariane/tlb_content.py
@@ -0,0 +1,125 @@
+from nmigen import Signal, Module, Cat, Const
+
+from ptw import TLBUpdate, PTE
+
+class TLBEntry:
+    def __init__(self, asid_width):
+        self.asid = Signal(asid_width)
+        # SV39 defines three levels of page tables
+        self.vpn0 = Signal(9)
+        self.vpn1 = Signal(9)
+        self.vpn2 = Signal(9)
+        self.is_2M = Signal()
+        self.is_1G = Signal()
+        self.valid = Signal()
+
+    def flatten(self):
+        return Cat(*self.ports())
+
+    def eq(self, x):
+        return self.flatten().eq(x.flatten())
+
+    def ports(self):
+        return [self.asid, self.vpn0, self.vpn1, self.vpn2,
+                self.is_2M, self.is_1G, self.valid]
+
+class TLBContent:
+    def __init__(self, pte_width, asid_width):
+        self.asid_width = asid_width
+        self.pte_width = pte_width
+        self.flush_i = Signal()  # Flush signal
+        # Update TLB
+        self.update_i = TLBUpdate()
+        self.vpn2 = Signal(9)
+        self.vpn1 = Signal(9)
+        self.vpn0 = Signal(9)
+        self.replace_en_i = Signal() # replace the following entry,
+                                     # set by replacement strategy
+        # Lookup signals
+        self.lu_asid_i = Signal(self.asid_width)
+        self.lu_content_o = Signal(self.pte_width)
+        self.lu_is_2M_o = Signal()
+        self.lu_is_1G_o = Signal()
+        self.lu_hit_o = Signal()
+
+    def elaborate(self, platform):
+        m = Module()
+
+        tags = TLBEntry(self.asid_width)
+        content = Signal(self.pte_width)
+
+        m.d.comb += [self.lu_hit_o.eq(0),
+                     self.lu_is_2M_o.eq(0),
+                     self.lu_is_1G_o.eq(0)]
+
+        # temporaries for 1st level match
+        asid_ok = Signal(reset_less=True)
+        vpn2_ok = Signal(reset_less=True)
+        tags_ok = Signal(reset_less=True)
+        vpn2_hit = Signal(reset_less=True)
+        m.d.comb += [tags_ok.eq(tags.valid),
+                     asid_ok.eq(tags.asid == self.lu_asid_i),
+                     vpn2_ok.eq(tags.vpn2 == self.vpn2),
+                     vpn2_hit.eq(tags_ok & asid_ok & vpn2_ok)]
+        # temporaries for 2nd level match
+        vpn1_ok = Signal(reset_less=True)
+        tags_2M = Signal(reset_less=True)
+        vpn0_ok = Signal(reset_less=True)
+        vpn0_or_2M = Signal(reset_less=True)
+        m.d.comb += [vpn1_ok.eq(self.vpn1 == tags.vpn1),
+                     tags_2M.eq(tags.is_2M),
+                     vpn0_ok.eq(self.vpn0 == tags.vpn0),
+                     vpn0_or_2M.eq(tags_2M | vpn0_ok)]
+        # first level match, this may be a giga page,
+        # check the ASID flags as well
+        with m.If(vpn2_hit):
+            # second level
+            with m.If (tags.is_1G):
+                m.d.comb += [ self.lu_content_o.eq(content),
+                              self.lu_is_1G_o.eq(1),
+                              self.lu_hit_o.eq(1),
+                            ]
+            # not a giga page hit so check further
+            with m.Elif(vpn1_ok):
+                # this could be a 2 mega page hit or a 4 kB hit
+                # output accordingly
+                with m.If(vpn0_or_2M):
+                    m.d.comb += [ self.lu_content_o.eq(content),
+                                  self.lu_is_2M_o.eq(tags.is_2M),
+                                  self.lu_hit_o.eq(1),
+                                ]
+        # ------------------
+        # Update or Flush
+        # ------------------
+
+        # temporaries
+        replace_valid = Signal(reset_less=True)
+        m.d.comb += replace_valid.eq(self.update_i.valid & self.replace_en_i)
+
+        # flush
+        with m.If (self.flush_i):
+            # invalidate (flush) conditions: all if zero or just this ASID
+            with m.If (self.lu_asid_i == Const(0, self.asid_width) |
+                      (self.lu_asid_i == tags.asid)):
+                m.d.sync += tags.valid.eq(0)
+
+        # normal replacement
+        with m.Elif(replace_valid):
+            m.d.sync += [ # update tag array
+                          tags.asid.eq(self.update_i.asid),
+                          tags.vpn2.eq(self.update_i.vpn[18:27]),
+                          tags.vpn1.eq(self.update_i.vpn[9:18]),
+                          tags.vpn0.eq(self.update_i.vpn[0:9]),
+                          tags.is_1G.eq(self.update_i.is_1G),
+                          tags.is_2M.eq(self.update_i.is_2M),
+                          tags.valid.eq(1),
+                          # and content as well
+                          content.eq(self.update_i.content.flatten())
+                        ]
+        return m
+
+    def ports(self):
+        return [self.flush_i,
+                 self.lu_asid_i,
+                 self.lu_is_2M_o, self.lu_is_1G_o, self.lu_hit_o,
+                ] + self.update_i.content.ports() + self.update_i.ports()
\ No newline at end of file
-- 
2.30.2