#
# 1:1 frequency-ratio Generic SDR PHY
#
# The GENSDRPHY is validated on CycloneIV (Altera) but since it does
# not use vendor-dependent code, it can also be used on other architectures.
#
# The PHY needs 2 Clock domains:
#  - sys_clk    : The System Clock domain
#  - sys_clk_ps : The System Clock domain with its phase shifted
#                 (-3ns on C4@100MHz)
#
# 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
# 4 cycles later, along with the assertion of
# dfi_rddata_valid.
#
# This PHY only supports CAS Latency 2.
#

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

from misoclib.sdram.bus.dfi import *
from misoclib import sdram

class GENSDRPHY(Module):
	def __init__(self, pads):
		a = flen(pads.a)
		ba = flen(pads.ba)
		d = flen(pads.dq)

		self.phy_settings = sdram.PhySettings(
			memtype="SDR",
			dfi_d=d,
			nphases=1,
			rdphase=0,
			wrphase=0,
			rdcmdphase=0,
			wrcmdphase=0,
			cl=2,
			read_latency=4,
			write_latency=0
		)

		self.dfi = Interface(a, ba, d)

		###

		#
		# Command/address
		#
		self.sync += [
			pads.a.eq(self.dfi.p0.address),
			pads.ba.eq(self.dfi.p0.bank),
			pads.cke.eq(self.dfi.p0.cke),
			pads.cas_n.eq(self.dfi.p0.cas_n),
			pads.ras_n.eq(self.dfi.p0.ras_n),
			pads.we_n.eq(self.dfi.p0.we_n)
		]
		if hasattr(pads, "cs_n"):
			self.sync += pads.cs_n.eq(self.dfi.p0.cs_n),

		#
		# DQ/DQS/DM data
		#
		sd_dq_out = Signal(d)
		drive_dq = Signal()
		self.sync += sd_dq_out.eq(self.dfi.p0.wrdata),
		self.specials += Tristate(pads.dq, sd_dq_out, drive_dq)
		self.sync += \
			If(self.dfi.p0.wrdata_en,
				pads.dm.eq(self.dfi.p0.wrdata_mask)
			).Else(
				pads.dm.eq(0)
			)
		sd_dq_in_ps = Signal(d)
		self.sync.sys_ps += sd_dq_in_ps.eq(pads.dq)
		self.sync += self.dfi.p0.rddata.eq(sd_dq_in_ps)

		#
		# DQ/DM control
		#
		d_dfi_wrdata_en = Signal()
		self.sync += d_dfi_wrdata_en.eq(self.dfi.p0.wrdata_en)
		self.comb += drive_dq.eq(d_dfi_wrdata_en)

		rddata_sr = Signal(4)
		self.comb += self.dfi.p0.rddata_valid.eq(rddata_sr[3])
		self.sync += rddata_sr.eq(Cat(self.dfi.p0.rddata_en, rddata_sr[:3]))