frontend/ecc: move generic part of ECC to LiteX

litedram/frontend/ecc.py

@@ -16,157 +16,15 @@ Limitations:
 - Byte enable not supported for writes.
 """
 
-from functools import reduce
-from operator import xor
-
 from migen import *
 
 from litex.soc.interconnect.csr import *
 from litex.soc.interconnect.stream import *
+from litex.soc.cores.ecc import *
 
 from litedram.common import wdata_description, rdata_description
 
 
-def compute_m_n(k):
-    m = 1
-    while (2**m < (m + k + 1)):
-        m = m + 1;
-    n = m + k
-    return m, n
-
-
-def compute_syndrome_positions(m):
-    r = []
-    i = 1
-    while i <= m:
-        r.append(i)
-        i = i << 1
-    return r
-
-
-def compute_data_positions(m):
-    r = []
-    e = compute_syndrome_positions(m)
-    for i in range(1, m + 1):
-        if not i in e:
-            r.append(i)
-    return r
-
-
-def compute_cover_positions(m, p):
-    r = []
-    i = p
-    while i <= m:
-        for j in range(min(p, m - i + 1)):
-            r.append(i + j)
-        i += 2*p
-    return r
-
-
-class SECDED:
-    def place_data(self, data, codeword):
-        d_pos = compute_data_positions(len(codeword))
-        for i, d in enumerate(d_pos):
-            self.comb += codeword[d-1].eq(data[i])
-
-    def extract_data(self, codeword, data):
-        d_pos = compute_data_positions(len(codeword))
-        for i, d in enumerate(d_pos):
-            self.comb += data[i].eq(codeword[d-1])
-
-    def compute_syndrome(self, codeword, syndrome):
-        p_pos = compute_syndrome_positions(len(codeword))
-        for i, p in enumerate(p_pos):
-            pn = Signal()
-            c_pos = compute_cover_positions(len(codeword), 2**i)
-            for c in c_pos:
-                new_pn = Signal()
-                self.comb += new_pn.eq(pn ^ codeword[c-1])
-                pn = new_pn
-            self.comb += syndrome[i].eq(pn)
-
-    def place_syndrome(self, syndrome, codeword):
-        p_pos = compute_syndrome_positions(len(codeword))
-        for i, p in enumerate(p_pos):
-            self.comb += codeword[p-1].eq(syndrome[i])
-
-    def compute_parity(self, codeword, parity):
-        self.comb += parity.eq(reduce(xor,
-            [codeword[i] for i in range(len(codeword))]))
-
-
-class ECCEncoder(SECDED, Module):
-    def __init__(self, k):
-        m, n = compute_m_n(k)
-
-        self.i = i = Signal(k)
-        self.o = o = Signal(n + 1)
-
-        # # #
-
-        syndrome = Signal(m)
-        parity = Signal()
-        codeword_d = Signal(n)
-        codeword_d_p = Signal(n)
-        codeword = Signal(n + 1)
-
-        # place data bits in codeword
-        self.place_data(i, codeword_d)
-        # compute and place syndrome bits
-        self.compute_syndrome(codeword_d, syndrome)
-        self.comb += codeword_d_p.eq(codeword_d)
-        self.place_syndrome(syndrome, codeword_d_p)
-        # compute parity
-        self.compute_parity(codeword_d_p, parity)
-        # output codeword + parity
-        self.comb += o.eq(Cat(parity, codeword_d_p))
-
-
-class ECCDecoder(SECDED, Module):
-    def __init__(self, k):
-        m, n = compute_m_n(k)
-
-        self.enable = Signal()
-        self.i = i = Signal(n + 1)
-        self.o = o = Signal(k)
-
-        self.sec = sec = Signal()
-        self.ded = ded = Signal()
-
-        # # #
-
-        syndrome = Signal(m)
-        parity = Signal()
-        codeword = Signal(n)
-        codeword_c = Signal(n)
-
-        # input codeword + parity
-        self.compute_parity(i, parity)
-        self.comb += codeword.eq(i[1:])
-        # compute_syndrome
-        self.compute_syndrome(codeword, syndrome)
-        self.comb += If(~self.enable, syndrome.eq(0))
-        # locate/correct codeword error bit if any and flip it
-        cases = {}
-        cases["default"] = codeword_c.eq(codeword)
-        for i in range(1, 2**len(syndrome)):
-            cases[i] = codeword_c.eq(codeword ^ (1<<(i-1)))
-        self.comb += Case(syndrome, cases)
-        # extract data / status
-        self.extract_data(codeword_c, o)
-        self.comb += [
-            If(syndrome != 0,
-                 # double error detected
-                If(~parity,
-                    ded.eq(1)
-                # single error corrected
-                ).Else(
-                    sec.eq(1)
-                )
-            )
-        ]
-
-
 class LiteDRAMNativePortECCW(Module):
     def __init__(self, data_width_from, data_width_to):
         self.sink = sink = Endpoint(wdata_description(data_width_from))

test/test_ecc.py

@@ -13,92 +13,6 @@ from litex.gen.sim import *
 
 
 class TestECC(unittest.TestCase):
-    def test_m_n(self):
-        m, n = compute_m_n(15)
-        self.assertEqual(m, 5)
-        self.assertEqual(n, 20)
-
-    def test_syndrome_positions(self):
-        p_pos = compute_syndrome_positions(20)
-        p_pos_ref = [1, 2, 4, 8, 16]
-        self.assertEqual(p_pos, p_pos_ref)
-
-    def test_data_positions(self):
-        d_pos = compute_data_positions(20)
-        d_pos_ref = [3, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20]
-        self.assertEqual(d_pos, d_pos_ref)
-
-    def test_cover_positions(self):
-        c_pos_ref = {
-            0 : [1, 3, 5, 7, 9, 11, 13, 15, 17, 19],
-            1 : [2, 3, 6, 7, 10, 11, 14, 15, 18, 19],
-            2 : [4, 5, 6, 7, 12, 13, 14, 15, 20],
-            3 : [8, 9, 10, 11, 12, 13, 14, 15],
-            4 : [16, 17, 18, 19, 20]
-        }
-        for i in range(5):
-            c_pos = compute_cover_positions(20, 2**i)
-            self.assertEqual(c_pos, c_pos_ref[i])
-
-    def test_ecc(self, k=15):
-        class DUT(Module):
-            def __init__(self, k):
-                m, n = compute_m_n(k)
-                self.flip = Signal(n + 1)
-
-                # # #
-
-                self.submodules.encoder = ECCEncoder(k)
-                self.submodules.decoder = ECCDecoder(k)
-
-                self.comb += self.decoder.i.eq(self.encoder.o ^ self.flip)
-
-        def generator(dut, k, nvalues, nerrors):
-            dut.errors = 0
-            prng = random.Random(42)
-            yield dut.decoder.enable.eq(1)
-            for i in range(nvalues):
-                data = prng.randrange(2**k-1)
-                yield dut.encoder.i.eq(data)
-                # FIXME: error when fliping parity bit
-                if nerrors == 1:
-                    flip_bit1 = (prng.randrange(len(dut.flip)-2) + 1)
-                    yield dut.flip.eq(1<<flip_bit1)
-                elif nerrors == 2:
-                    flip_bit1 = (prng.randrange(len(dut.flip)-2) + 1)
-                    flip_bit2 = flip_bit1
-                    while flip_bit2 == flip_bit1:
-                        flip_bit2 = (prng.randrange(len(dut.flip)-2) + 1)
-                    yield dut.flip.eq((1<<flip_bit1) | (1<<flip_bit2))
-                yield
-                # if less than 2 errors, check data
-                if nerrors < 2:
-                    if (yield dut.decoder.o) != data:
-                        dut.errors += 1
-                # if 0 error, verify sec == 0 / ded == 0
-                if nerrors == 0:
-                    if (yield dut.decoder.sec) != 0:
-                        dut.errors += 1
-                    if (yield dut.decoder.ded) != 0:
-                        dut.errors += 1
-                # if 1 error, verify sec == 1 / dec == 0
-                elif nerrors == 1:
-                    if (yield dut.decoder.sec) != 1:
-                        dut.errors += 1
-                    if (yield dut.decoder.ded) != 0:
-                        dut.errors += 1
-                # if 2 errors, verify sec == 0 / ded == 1
-                elif nerrors == 2:
-                    if (yield dut.decoder.sec) != 0:
-                        dut.errors += 1
-                    if (yield dut.decoder.ded) != 1:
-                        dut.errors += 1
-
-        for i in range(3):
-            dut = DUT(k)
-            run_simulation(dut, generator(dut, k, 128, i))
-            self.assertEqual(dut.errors, 0)
-
     def test_ecc_wrapper(self):
         # 32 bits + 8 bits ecc
         port_from = LiteDRAMNativePort("both", 24, 32*8)