added spi 1-bit mode, code from litex

Author: danielkucera

misoc/cores/spi_flash.py

@@ -25,7 +25,7 @@ def _format_cmd(cmd, spi_width):
     return c
 
 
-class SpiFlash(Module, AutoCSR):
+class SpiFlashDualQuad(Module, AutoCSR):
     def __init__(self, pads, dummy=15, div=2, with_bitbang=True):
         """
         Simple SPI flash, e.g. N25Q128 on the LX9 Microboard.
@@ -147,3 +147,88 @@ def __init__(self, pads, dummy=15, div=2, with_bitbang=True):
             t += dt
 
         self.sync += timeline(bus.cyc & bus.stb & (i == div - 1), tseq)
+
+class SpiFlashSingle(Module, AutoCSR):
+    def __init__(self, pads, dummy=15, div=2):
+        """
+        Simple SPI flash.
+        Supports 1-bit reads. Only supports mode0 (cpol=0, cpha=0).
+        """
+        self.bus = bus = wishbone.Interface()
+
+        # # #
+
+        if hasattr(pads, "wp"):
+            self.comb += pads.wp.eq(1)
+
+        if hasattr(pads, "hold"):
+            self.comb += pads.hold.eq(1)
+
+        cs_n = Signal(reset=1)
+        clk = Signal()
+        wbone_width = len(bus.dat_r)
+
+        read_cmd = _FAST_READ
+        cmd_width = 8
+        addr_width = 24
+
+        sr = Signal(max(cmd_width, addr_width, wbone_width))
+        self.comb += bus.dat_r.eq(sr)
+
+        self.comb += [
+            pads.clk.eq(clk),
+            pads.cs_n.eq(cs_n),
+            pads.mosi.eq(sr[-1:])
+        ]
+
+        if div < 2:
+            raise ValueError("Unsupported value \'{}\' for div parameter for SpiFlash core".format(div))
+        else:
+            i = Signal(max=div)
+            miso = Signal()
+            self.sync += [
+                If(i == div//2 - 1,
+                    clk.eq(1),
+                    miso.eq(pads.miso),
+                ),
+                If(i == div - 1,
+                    i.eq(0),
+                    clk.eq(0),
+                    sr.eq(Cat(miso, sr[:-1]))
+                ).Else(
+                    i.eq(i + 1),
+                ),
+            ]
+
+        # spi is byte-addressed, prefix by zeros
+        z = Replicate(0, log2_int(wbone_width//8))
+
+        seq = [
+            (cmd_width*div,
+                [cs_n.eq(0), sr[-cmd_width:].eq(read_cmd)]),
+            (addr_width*div,
+                [sr[-addr_width:].eq(Cat(z, bus.adr))]),
+            ((dummy + wbone_width)*div,
+                []),
+            (1,
+                [bus.ack.eq(1), cs_n.eq(1)]),
+            (div, # tSHSL!
+                [bus.ack.eq(0)]),
+            (0,
+                []),
+        ]
+
+        # accumulate timeline deltas
+        t, tseq = 0, []
+        for dt, a in seq:
+            tseq.append((t, a))
+            t += dt
+
+        self.sync += timeline(bus.cyc & bus.stb & (i == div - 1), tseq)
+
+
+def SpiFlash(pads, *args, **kw):
+    if hasattr(pads, "mosi"):
+        return SpiFlashSingle(pads, *args, **kw)
+    else:
+        return SpiFlashDualQuad(pads, *args, **kw)