analog_pocket: Add 1:2 (HalfRate) SDRAM support.

litex_boards/targets/analog_pocket.py

@@ -6,7 +6,7 @@
 # Copyright (c) 2023 Florent Kermarrec <florent@enjoy-digital.fr>
 # SPDX-License-Identifier: BSD-2-Clause
 
-# ./analog_pocket.py --uart-name=jtag_uart --build --load
+# ./analog_pocket.py --sdram-rate=1:2 --uart-name=jtag_uart --build --load
 # litex_term jtag --jtag-config=openocd_usb_blaster.cfg
 
 from migen import *
@@ -23,15 +23,19 @@ from litex.build.io import DDROutput
 from litex.soc.cores.clock import CycloneVPLL
 
 from litedram.modules import AS4C32M16
-from litedram.phy import GENSDRPHY
+from litedram.phy import GENSDRPHY, HalfRateGENSDRPHY
 
 # CRG ----------------------------------------------------------------------------------------------
 
 class _CRG(LiteXModule):
-    def __init__(self, platform, sys_clk_freq):
+    def __init__(self, platform, sys_clk_freq, sdram_rate="1:1"):
         self.rst       = Signal()
         self.cd_sys    = ClockDomain()
-        self.cd_sys_ps = ClockDomain()
+        if sdram_rate == "1:2":
+            self.cd_sys2x    = ClockDomain()
+            self.cd_sys2x_ps = ClockDomain()
+        else:
+            self.cd_sys_ps = ClockDomain()
 
         # # #
 
@@ -43,30 +47,35 @@ class _CRG(LiteXModule):
         self.comb += pll.reset.eq(self.rst)
         pll.register_clkin(clk74, 74.25e6)
         pll.create_clkout(self.cd_sys,    sys_clk_freq)
-        pll.create_clkout(self.cd_sys_ps, sys_clk_freq, phase=90)
+        if sdram_rate == "1:2":
+            pll.create_clkout(self.cd_sys2x,    2*sys_clk_freq)
+            pll.create_clkout(self.cd_sys2x_ps, 2*sys_clk_freq, phase=180)  # Idealy 90° but needs to be increased.
+        else:
+            pll.create_clkout(self.cd_sys_ps, sys_clk_freq, phase=90)
 
         # SDRAM clock
-        sdram_clk = ClockSignal("sys_ps")
+        sdram_clk = ClockSignal("sys2x_ps" if sdram_rate == "1:2" else "sys_ps")
         self.specials += DDROutput(1, 0, platform.request("sdram_clock"), sdram_clk)
 
 # BaseSoC ------------------------------------------------------------------------------------------
 
 class BaseSoC(SoCCore):
-    def __init__(self, sys_clk_freq=50e6, **kwargs):
+    def __init__(self, sys_clk_freq=50e6, sdram_rate="1:1", **kwargs):
         platform = analog_pocket.Platform()
 
         # CRG --------------------------------------------------------------------------------------
-        self.crg = _CRG(platform, sys_clk_freq)
+        self.crg = _CRG(platform, sys_clk_freq, sdram_rate)
 
         # SoCCore ----------------------------------------------------------------------------------
         SoCCore.__init__(self, platform, sys_clk_freq, ident="LiteX SoC on Analog Pocket", **kwargs)
 
         # SDR SDRAM --------------------------------------------------------------------------------
         if not self.integrated_main_ram_size:
-            self.sdrphy = GENSDRPHY(platform.request("sdram"), sys_clk_freq)
+            sdrphy_cls = HalfRateGENSDRPHY if sdram_rate == "1:2" else GENSDRPHY
+            self.sdrphy = sdrphy_cls(platform.request("sdram"), sys_clk_freq)
             self.add_sdram("sdram",
                 phy           = self.sdrphy,
-                module        = AS4C32M16(sys_clk_freq, "1:1"),
+                module        = AS4C32M16(sys_clk_freq, sdram_rate),
                 l2_cache_size = kwargs.get("l2_size", 8192)
             )
 
@@ -76,10 +85,12 @@ def main():
     from litex.build.parser import LiteXArgumentParser
     parser = LiteXArgumentParser(platform=analog_pocket.Platform, description="LiteX SoC on Analog Pocket.")
     parser.add_target_argument("--sys-clk-freq", default=50e6, type=float, help="System clock frequency.")
+    parser.add_target_argument("--sdram-rate",   default="1:1",            help="SDRAM Rate (1:1 Full Rate or 1:2 Half Rate).")
     args = parser.parse_args()
 
     soc = BaseSoC(
         sys_clk_freq = args.sys_clk_freq,
+        sdram_rate   = args.sdram_rate,
         **parser.soc_argdict
     )
     builder = Builder(soc, **parser.builder_argdict)