Move MemorySet into separate file

[soc.git] / TLB / src / MemorySet.py

diff --git a/TLB/src/MemorySet.py b/TLB/src/MemorySet.py
new file mode 100644 (file)
index 0000000..d081dcd
--- /dev/null
+++ b/TLB/src/MemorySet.py
@@ -0,0 +1,65 @@
+from nmigen import Cat, Memory, Module, Signal
+from nmigen.cli import main
+from nmigen.cli import verilog, rtlil
+
+class MemorySet:
+    def __init__(self, data_size, tag_size, set_count, active):
+        self.active = active
+        input_size = tag_size + data_size # Size of the input data
+        memory_width = input_size + 1 # The width of the cache memory
+        self.active = active
+        self.data_size = data_size
+        self.tag_size = tag_size
+
+        # XXX TODO, use rd-enable and wr-enable?
+        self.mem = Memory(memory_width, set_count)
+        self.r = self.mem.read_port()
+        self.w = self.mem.write_port()
+
+        # inputs (address)
+        self.cset = Signal(max=set_count)  # The set to be checked
+        self.tag = Signal(tag_size)        # The tag to find
+        self.data_i = Signal(data_size)    # Incoming data
+
+        # outputs
+        self.valid = Signal()
+        self.data_o = Signal(data_size)    # Outgoing data (excludes tag)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.submodules.mem = self.mem
+        m.submodules.r = self.r
+        m.submodules.w = self.w
+
+        # temporaries
+        active_bit = Signal()
+        tag_valid = Signal()
+        data_start = self.active + 1
+        data_end = data_start + self.data_size
+        tag_start = data_end
+        tag_end = tag_start + self.tag_size
+
+        # connect the read port address to the set/entry
+        read_port = self.r
+        m.d.comb += read_port.addr.eq(self.cset)
+        # Pull out active bit from data
+        data = read_port.data
+        m.d.comb += active_bit.eq(data[self.active])
+        # Validate given tag vs stored tag
+        tag = data[tag_start:tag_end]
+        m.d.comb += tag_valid.eq(self.tag == tag)
+        # An entry is only valid if the tags match AND
+        # is marked as a valid entry
+        m.d.comb += self.valid.eq(tag_valid & active_bit)
+
+        # output data: TODO, check rd-enable?
+        m.d.comb += self.data_o.eq(data[data_start:data_end])
+
+        # connect the write port addr to the set/entry (only if write enabled)
+        # (which is only done on a match, see SAC.write_entry below)
+        write_port = self.w
+        with m.If(write_port.en):
+            m.d.comb += write_port.addr.eq(self.cset)
+            m.d.comb += write_port.data.eq(Cat(1, self.data_i, self.tag))
+
+        return m
\ No newline at end of file