litex/misoclib/mem/sdram/phy/s6ddrphy.py

# 1:2 frequency-ratio DDR / LPDDR / DDR2 PHY for Spartan-6
#
# Assert dfi_wrdata_en and present the data
# on dfi_wrdata_mask/dfi_wrdata in the same
# cycle as the write command.
#
# Assert dfi_rddata_en in the same cycle as the read
# command. The data will come back on dfi_rddata
# 5 cycles later, along with the assertion
# of dfi_rddata_valid.
#
# This PHY only supports CAS Latency 3.
# Read commands must be sent on phase 0.
# Write commands must be sent on phase 1.
#

from migen.fhdl.std import *
from migen.genlib.record import *

from misoclib.mem.sdram.phy.dfi import *
from misoclib.mem import sdram


class S6DDRPHY(Module):
    def __init__(self, pads, module, rd_bitslip, wr_bitslip, dqs_ddr_alignment):
        if module.memtype not in ["DDR", "LPDDR", "DDR2"]:
            raise NotImplementedError("S6DDRPHY only supports DDR, LPDDR and DDR2")
        addressbits = flen(pads.a)
        bankbits = flen(pads.ba)
        databits = flen(pads.dq)
        nphases = 2

        self.settings = sdram.PhySettings(
            memtype=module.memtype,
            dfi_databits=2*databits,
            nphases=nphases,
            rdphase=0,
            wrphase=1,
            rdcmdphase=1,
            wrcmdphase=0,
            cl=3,
            read_latency=5,
            write_latency=0
        )
        self.module = module

        self.dfi = Interface(addressbits, bankbits, 2*databits, nphases)
        self.clk4x_wr_strb = Signal()
        self.clk4x_rd_strb = Signal()

        ###

        # sys_clk           : system clk, used for dfi interface
        # sdram_half_clk    : half rate sdram clk
        # sdram_full_wr_clk : full rate sdram write clk
        # sdram_full_rd_clk : full rate sdram read clk
        sd_sys = getattr(self.sync, "sys")
        sd_sdram_half = getattr(self.sync, "sdram_half")

        sys_clk = ClockSignal("sys")
        sdram_half_clk = ClockSignal("sdram_half")
        sdram_full_wr_clk = ClockSignal("sdram_full_wr")
        sdram_full_rd_clk = ClockSignal("sdram_full_rd")

        #
        # Command/address
        #

        # select active phase
        #             sys_clk   ----____----____
        #  phase_sel(nphases=2) 0   1   0   1     Half Rate
        phase_sel = Signal(log2_int(nphases))
        phase_half = Signal.like(phase_sel)
        phase_sys = Signal.like(phase_half)

        sd_sys += phase_sys.eq(phase_half)

        sd_sdram_half += [
            If(phase_half == phase_sys,
                phase_sel.eq(0),
            ).Else(
                phase_sel.eq(phase_sel+1)
            ),
            phase_half.eq(phase_half+1),
        ]

        # register dfi cmds on half_rate clk
        r_dfi = Array(Record(phase_cmd_description(addressbits, bankbits)) for i in range(nphases))
        for n, phase in enumerate(self.dfi.phases):
            sd_sdram_half += [
                r_dfi[n].address.eq(phase.address),
                r_dfi[n].bank.eq(phase.bank),
                r_dfi[n].cs_n.eq(phase.cs_n),
                r_dfi[n].cke.eq(phase.cke),
                r_dfi[n].cas_n.eq(phase.cas_n),
                r_dfi[n].ras_n.eq(phase.ras_n),
                r_dfi[n].we_n.eq(phase.we_n)
            ]

        # output cmds
        sd_sdram_half += [
            pads.a.eq(r_dfi[phase_sel].address),
            pads.ba.eq(r_dfi[phase_sel].bank),
            pads.cke.eq(r_dfi[phase_sel].cke),
            pads.ras_n.eq(r_dfi[phase_sel].ras_n),
            pads.cas_n.eq(r_dfi[phase_sel].cas_n),
            pads.we_n.eq(r_dfi[phase_sel].we_n)
        ]
        if hasattr(pads, "cs_n"):
            sd_sdram_half += pads.cs_n.eq(r_dfi[phase_sel].cs_n)

        #
        # Bitslip
        #
        bitslip_cnt = Signal(4)
        bitslip_inc = Signal()

        sd_sys += [
            If(bitslip_cnt == rd_bitslip,
                bitslip_inc.eq(0)
            ).Else(
                bitslip_cnt.eq(bitslip_cnt+1),
                bitslip_inc.eq(1)
            )
        ]

        #
        # DQ/DQS/DM data
        #
        sdram_half_clk_n = Signal()
        self.comb += sdram_half_clk_n.eq(~sdram_half_clk)

        postamble = Signal()
        drive_dqs = Signal()
        dqs_t_d0 = Signal()
        dqs_t_d1 = Signal()

        dqs_o = Signal(databits//8)
        dqs_t = Signal(databits//8)

        self.comb += [
            dqs_t_d0.eq(~(drive_dqs | postamble)),
            dqs_t_d1.eq(~drive_dqs),
        ]

        for i in range(databits//8):
            # DQS output
            self.specials += Instance("ODDR2",
                p_DDR_ALIGNMENT=dqs_ddr_alignment,
                p_INIT=0,
                p_SRTYPE="ASYNC",

                i_C0=sdram_half_clk,
                i_C1=sdram_half_clk_n,

                i_CE=1,
                i_D0=0,
                i_D1=1,
                i_R=0,
                i_S=0,

                o_Q=dqs_o[i]
            )

            # DQS tristate cmd
            self.specials += Instance("ODDR2",
                p_DDR_ALIGNMENT=dqs_ddr_alignment,
                p_INIT=0,
                p_SRTYPE="ASYNC",

                i_C0=sdram_half_clk,
                i_C1=sdram_half_clk_n,

                i_CE=1,
                i_D0=dqs_t_d0,
                i_D1=dqs_t_d1,
                i_R=0,
                i_S=0,

                o_Q=dqs_t[i]
            )

            # DQS tristate buffer
            if hasattr(pads, "dqs_n"):
                self.specials += Instance("OBUFTDS",
                    i_I=dqs_o[i],
                    i_T=dqs_t[i],

                    o_O=pads.dqs[i],
                    o_OB=pads.dqs_n[i],
                )
            else:
                self.specials += Instance("OBUFT",
                    i_I=dqs_o[i],
                    i_T=dqs_t[i],

                    o_O=pads.dqs[i]
                )

        sd_sdram_half += postamble.eq(drive_dqs)

        d_dfi = [Record(phase_wrdata_description(nphases*databits)+phase_rddata_description(nphases*databits))
            for i in range(2*nphases)]

        for n, phase in enumerate(self.dfi.phases):
            self.comb += [
                d_dfi[n].wrdata.eq(phase.wrdata),
                d_dfi[n].wrdata_mask.eq(phase.wrdata_mask),
                d_dfi[n].wrdata_en.eq(phase.wrdata_en),
                d_dfi[n].rddata_en.eq(phase.rddata_en),
            ]
            sd_sys += [
                d_dfi[nphases+n].wrdata.eq(phase.wrdata),
                d_dfi[nphases+n].wrdata_mask.eq(phase.wrdata_mask)
            ]


        drive_dq = Signal()
        drive_dq_n = [Signal() for i in range(2)]
        self.comb += drive_dq_n[0].eq(~drive_dq)
        sd_sys += drive_dq_n[1].eq(drive_dq_n[0])

        dq_t = Signal(databits)
        dq_o = Signal(databits)
        dq_i = Signal(databits)

        dq_wrdata = []
        for i in range(2):
            for j in reversed(range(nphases)):
                dq_wrdata.append(d_dfi[i*nphases+j].wrdata[:databits])
                dq_wrdata.append(d_dfi[i*nphases+j].wrdata[databits:])

        for i in range(databits):
            # Data serializer
            self.specials += Instance("OSERDES2",
                p_DATA_WIDTH=4,
                p_DATA_RATE_OQ="SDR",
                p_DATA_RATE_OT="SDR",
                p_SERDES_MODE="NONE",
                p_OUTPUT_MODE="SINGLE_ENDED",

                o_OQ=dq_o[i],
                i_OCE=1,
                i_CLK0=sdram_full_wr_clk,
                i_CLK1=0,
                i_IOCE=self.clk4x_wr_strb,
                i_RST=0,
                i_CLKDIV=sys_clk,

                i_D1=dq_wrdata[wr_bitslip+3][i],
                i_D2=dq_wrdata[wr_bitslip+2][i],
                i_D3=dq_wrdata[wr_bitslip+1][i],
                i_D4=dq_wrdata[wr_bitslip+0][i],

                o_TQ=dq_t[i],
                i_T1=drive_dq_n[(wr_bitslip+3)//4],
                i_T2=drive_dq_n[(wr_bitslip+2)//4],
                i_T3=drive_dq_n[(wr_bitslip+1)//4],
                i_T4=drive_dq_n[(wr_bitslip+0)//4],
                i_TRAIN=0,
                i_TCE=1,
                i_SHIFTIN1=0,
                i_SHIFTIN2=0,
                i_SHIFTIN3=0,
                i_SHIFTIN4=0,
            )

            # Data deserializer
            self.specials += Instance("ISERDES2",
                p_DATA_WIDTH=4,
                p_DATA_RATE="SDR",
                p_BITSLIP_ENABLE="TRUE",
                p_SERDES_MODE="NONE",
                p_INTERFACE_TYPE="RETIMED",

                i_D=dq_i[i],
                i_CE0=1,
                i_CLK0=sdram_full_rd_clk,
                i_CLK1=0,
                i_IOCE=self.clk4x_rd_strb,
                i_RST=ResetSignal(),
                i_CLKDIV=sys_clk,
                i_BITSLIP=bitslip_inc,

                o_Q1=d_dfi[0*nphases+0].rddata[i+databits],
                o_Q2=d_dfi[0*nphases+0].rddata[i],
                o_Q3=d_dfi[0*nphases+1].rddata[i+databits],
                o_Q4=d_dfi[0*nphases+1].rddata[i],
            )

            # Data buffer
            self.specials += Instance("IOBUF",
                i_I=dq_o[i],
                o_O=dq_i[i],
                i_T=dq_t[i],
                io_IO=pads.dq[i]
            )

        dq_wrdata_mask = []
        for i in range(2):
            for j in reversed(range(nphases)):
                dq_wrdata_mask.append(d_dfi[i*nphases+j].wrdata_mask[:databits//8])
                dq_wrdata_mask.append(d_dfi[i*nphases+j].wrdata_mask[databits//8:])

        for i in range(databits//8):
            # Mask serializer
            self.specials += Instance("OSERDES2",
                p_DATA_WIDTH=4,
                p_DATA_RATE_OQ="SDR",
                p_DATA_RATE_OT="SDR",
                p_SERDES_MODE="NONE",
                p_OUTPUT_MODE="SINGLE_ENDED",

                o_OQ=pads.dm[i],
                i_OCE=1,
                i_CLK0=sdram_full_wr_clk,
                i_CLK1=0,
                i_IOCE=self.clk4x_wr_strb,
                i_RST=0,
                i_CLKDIV=sys_clk,

                i_D1=dq_wrdata_mask[wr_bitslip+3][i],
                i_D2=dq_wrdata_mask[wr_bitslip+2][i],
                i_D3=dq_wrdata_mask[wr_bitslip+1][i],
                i_D4=dq_wrdata_mask[wr_bitslip+0][i],

                i_TRAIN=0,
                i_TCE=0,
                i_SHIFTIN1=0,
                i_SHIFTIN2=0,
                i_SHIFTIN3=0,
                i_SHIFTIN4=0,
            )

        #
        # ODT
        #
        # ODT not yet supported
        if hasattr(pads, "odt"):
            self.comb += pads.odt.eq(0)

        #
        # DQ/DQS/DM control
        #
        self.comb += drive_dq.eq(d_dfi[self.settings.wrphase].wrdata_en)

        d_dfi_wrdata_en = Signal()
        sd_sys += d_dfi_wrdata_en.eq(d_dfi[self.settings.wrphase].wrdata_en)

        r_dfi_wrdata_en = Signal(2)
        sd_sdram_half += r_dfi_wrdata_en.eq(Cat(d_dfi_wrdata_en, r_dfi_wrdata_en[0]))

        self.comb += drive_dqs.eq(r_dfi_wrdata_en[1])

        rddata_sr = Signal(self.settings.read_latency)
        sd_sys += rddata_sr.eq(Cat(rddata_sr[1:self.settings.read_latency],
            d_dfi[self.settings.rdphase].rddata_en))

        for n, phase in enumerate(self.dfi.phases):
            self.comb += [
                phase.rddata.eq(d_dfi[n].rddata),
                phase.rddata_valid.eq(rddata_sr[0]),
            ]