memtest/MemtestWriter: fix 'busy status stuck' bug

diff --git a/milkymist/memtest/__init__.py b/milkymist/memtest/__init__.py
index 7434cd55dd7e9e16cf2ee432a5525f8a8604e4d3..61914b13ea31eb8cd5e573d312d8070905ed7301 100644 (file)
--- a/milkymist/memtest/__init__.py
+++ b/milkymist/memtest/__init__.py
@@ -2,7 +2,7 @@ from migen.fhdl.std import *
 from migen.genlib.misc import optree
 from migen.bank.description import *
 from migen.actorlib import dma_lasmi
-from migen.actorlib.spi import MODE_SINGLE_SHOT, DMAReadController, DMAWriteController
+from migen.actorlib.spi import *
 
 class LFSR(Module):
        def __init__(self, n_out, n_state=31, taps=[27, 30]):
@@ -53,7 +53,8 @@ class MemtestWriter(Module):
        def __init__(self, lasmim):
                self._r_magic = CSRStatus(16)
                self._r_reset = CSR()
-               self.submodules._dma = DMAWriteController(dma_lasmi.Writer(lasmim), MODE_SINGLE_SHOT)
+               self._r_shoot = CSR()
+               self.submodules._dma = DMAWriteController(dma_lasmi.Writer(lasmim), MODE_EXTERNAL)
 
                ###
 
@@ -63,14 +64,26 @@ class MemtestWriter(Module):
                self.submodules += lfsr
                self.comb += lfsr.reset.eq(self._r_reset.re)
 
+               en = Signal()
+               en_counter = Signal(lasmim.aw)
+               self.comb += en.eq(en_counter != 0)
+               self.sync += [
+                       If(self._r_shoot.re,
+                               en_counter.eq(self._dma.length)
+                       ).Elif(lfsr.ce,
+                               en_counter.eq(en_counter - 1)
+                       )
+               ]
+
                self.comb += [
-                       self._dma.data.stb.eq(1),
-                       lfsr.ce.eq(self._dma.data.ack),
+                       self._dma.trigger.eq(self._r_shoot.re),
+                       self._dma.data.stb.eq(en),
+                       lfsr.ce.eq(en & self._dma.data.ack),
                        self._dma.data.payload.d.eq(lfsr.o)
                ]
 
        def get_csrs(self):
-               return [self._r_magic, self._r_reset] + self._dma.get_csrs()
+               return [self._r_magic, self._r_reset, self._r_shoot] + self._dma.get_csrs()
 
 class MemtestReader(Module):
        def __init__(self, lasmim):