From e3461704b5280e34bd3b3bd386b12129ad414998 Mon Sep 17 00:00:00 2001 From: Florent Kermarrec Date: Thu, 1 Oct 2020 18:30:17 +0200 Subject: [PATCH] phy/ecp5/s7/usddrphy: simplify control path using TappedDelayLine. --- litedram/phy/ecp5ddrphy.py | 47 ++++++++++++++++++++------------------ litedram/phy/s7ddrphy.py | 38 +++++++++++++++++------------- litedram/phy/usddrphy.py | 36 ++++++++++++++++------------- 3 files changed, 67 insertions(+), 54 deletions(-) diff --git a/litedram/phy/ecp5ddrphy.py b/litedram/phy/ecp5ddrphy.py index ec5aa6d..b1be838 100644 --- a/litedram/phy/ecp5ddrphy.py +++ b/litedram/phy/ecp5ddrphy.py @@ -362,40 +362,43 @@ class ECP5DDRPHY(Module, AutoCSR): ] # Read Control Path ------------------------------------------------------------------------ - # Creates a shift register of read commands coming from the DFI interface. This shift register - # is used to control DQS read (internal read pulse of the DQSBUF) and to indicate to the - # DFI interface that the read data is valid. + # Creates a delay line of read commands coming from the DFI interface. The taps are used to + # control DQS read (internal read pulse of the DQSBUF) and the output of the delay is used + # signal a valid read data to the DFI interface. # # The DQS read must be asserted for 2 sys_clk cycles before the read data is coming back from # the DRAM (see 6.2.4 READ Pulse Positioning Optimization of FPGA-TN-02035-1.2) # # The read data valid is asserted for 1 sys_clk cycle when the data is available on the DFI # interface, the latency is the sum of the ODDRX2DQA, CAS, IDDRX2DQA latencies. - rddata_en = Signal(self.settings.read_latency) - rddata_en_last = Signal.like(rddata_en) - self.comb += rddata_en.eq(Cat(reduce(or_, [dfi.phases[i].rddata_en for i in range(nphases)]), rddata_en_last)) - self.sync += rddata_en_last.eq(rddata_en) - self.sync += [phase.rddata_valid.eq(rddata_en[-1]) for phase in dfi.phases] - self.comb += dqs_re.eq(rddata_en[cl_sys_latency + 1] | rddata_en[cl_sys_latency + 2]) + rddata_en = TappedDelayLine( + signal = reduce(or_, [dfi.phases[i].rddata_en for i in range(nphases)]), + ntaps = self.settings.read_latency + ) + self.submodules += rddata_en + self.sync += [phase.rddata_valid.eq(rddata_en.output) for phase in dfi.phases] + self.comb += dqs_re.eq(rddata_en.taps[cl_sys_latency + 1] | rddata_en.taps[cl_sys_latency + 2]) # Write Control Path ----------------------------------------------------------------------- - # Creates a shift register of write commands coming from the DFI interface. This shift register - # is used to control DQ/DQS tristates and to select write data of the DRAM burst from the DFI - # interface: The PHY is operating in halfrate mode (so provide 4 datas every sys_clk cycles: - # 2x for DDR, 2x for halfrate) but DDR3 requires a burst of 8 datas (BL8) for best efficiency. - # Writes are then performed in 2 sys_clk cycles and data needs to be selected for each cycle. - wrdata_en = Signal(cwl_sys_latency + 4) - wrdata_en_last = Signal.like(wrdata_en) - self.comb += wrdata_en.eq(Cat(reduce(or_, [dfi.phases[i].wrdata_en for i in range(nphases)]), wrdata_en_last)) - self.sync += wrdata_en_last.eq(wrdata_en) - self.comb += dq_oe.eq(wrdata_en[cwl_sys_latency + 1] | wrdata_en[cwl_sys_latency + 2]) - self.comb += bl8_chunk.eq(wrdata_en[cwl_sys_latency + 1]) + # Create a delay line of write commands coming from the DFI interface. This taps are used to + # control DQ/DQS tristates and to select write data of the DRAM burst from the DFI interface. + # The PHY is operating in halfrate mode (so provide 4 datas every sys_clk cycles: 2x for DDR, + # 2x for halfrate) but DDR3 requires a burst of 8 datas (BL8) for best efficiency. Writes are + # then performed in 2 sys_clk cycles and data needs to be selected for each cycle. + wrdata_en = TappedDelayLine( + signal = reduce(or_, [dfi.phases[i].wrdata_en for i in range(nphases)]), + ntaps = cwl_sys_latency + 4 + ) + self.submodules += wrdata_en + + self.comb += dq_oe.eq(wrdata_en.taps[cwl_sys_latency + 1] | wrdata_en.taps[cwl_sys_latency + 2]) + self.comb += bl8_chunk.eq(wrdata_en.taps[cwl_sys_latency + 1]) self.comb += dqs_oe.eq(dq_oe) # Write DQS Postamble/Preamble Control Path ------------------------------------------------ # Generates DQS Preamble 1 cycle before the first write and Postamble 1 cycle after the last # write. During writes, DQS tristate is configured as output for at least 4 sys_clk cycles: # 1 for Preamble, 2 for the Write and 1 for the Postamble. - self.comb += dqs_preamble.eq( wrdata_en[cwl_sys_latency + 0] & ~wrdata_en[cwl_sys_latency + 1]) - self.comb += dqs_postamble.eq(wrdata_en[cwl_sys_latency + 3] & ~wrdata_en[cwl_sys_latency + 2]) + self.comb += dqs_preamble.eq( wrdata_en.taps[cwl_sys_latency + 0] & ~wrdata_en.taps[cwl_sys_latency + 1]) + self.comb += dqs_postamble.eq(wrdata_en.taps[cwl_sys_latency + 3] & ~wrdata_en.taps[cwl_sys_latency + 2]) diff --git a/litedram/phy/s7ddrphy.py b/litedram/phy/s7ddrphy.py index 002410e..d4594cf 100644 --- a/litedram/phy/s7ddrphy.py +++ b/litedram/phy/s7ddrphy.py @@ -391,33 +391,39 @@ class S7DDRPHY(Module, AutoCSR): ] # Read Control Path ------------------------------------------------------------------------ - # Creates a shift register of read commands coming from the DFI interface. This shift register - # is used to indicate to the DFI interface that the read data is valid. + # Creates a delay line of read commands coming from the DFI interface. The output is used to + # signal a valid read data to the DFI interface. # # The read data valid is asserted for 1 sys_clk cycle when the data is available on the DFI # interface, the latency is the sum of the OSERDESE2, CAS, ISERDESE2 and Bitslip latencies. - rddata_en = Signal(self.settings.read_latency) - rddata_en_last = Signal.like(rddata_en) - self.comb += rddata_en.eq(Cat(reduce(or_, [dfi.phases[i].rddata_en for i in range(nphases)]), rddata_en_last)) - self.sync += rddata_en_last.eq(rddata_en) - self.sync += [phase.rddata_valid.eq(rddata_en[-1] | self._wlevel_en.storage) for phase in dfi.phases] + rddata_en = TappedDelayLine( + signal = reduce(or_, [dfi.phases[i].rddata_en for i in range(nphases)]), + ntaps = self.settings.read_latency + ) + self.submodules += rddata_en + + self.sync += [phase.rddata_valid.eq(rddata_en.output | self._wlevel_en.storage) for phase in dfi.phases] # Write Control Path ----------------------------------------------------------------------- - # Creates a shift register of write commands coming from the DFI interface. This shift register - # is used to control DQ/DQS tristates. - wrdata_en = Signal(cwl_sys_latency + 2) - wrdata_en_last = Signal.like(wrdata_en) - self.comb += wrdata_en.eq(Cat(reduce(or_, [dfi.phases[i].wrdata_en for i in range(nphases)]), wrdata_en_last)) - self.sync += wrdata_en_last.eq(wrdata_en) - self.comb += dq_oe.eq(wrdata_en[cwl_sys_latency]) + dq_latency = cwl_sys_latency + + # Create a delay line of write commands coming from the DFI interface. This taps are used to + # control DQ/DQS tristates. + wrdata_en = TappedDelayLine( + signal = reduce(or_, [dfi.phases[i].wrdata_en for i in range(nphases)]), + ntaps = dq_latency + 2 + ) + self.submodules += wrdata_en + + self.comb += dq_oe.eq(wrdata_en.taps[cwl_sys_latency]) self.comb += If(self._wlevel_en.storage, dqs_oe.eq(1)).Else(dqs_oe.eq(dq_oe)) # Write DQS Postamble/Preamble Control Path ------------------------------------------------ # Generates DQS Preamble 1 cycle before the first write and Postamble 1 cycle after the last # write. During writes, DQS tristate is configured as output for at least 3 sys_clk cycles: # 1 for Preamble, 1 for the Write and 1 for the Postamble. - self.comb += dqs_pattern.preamble.eq( wrdata_en[cwl_sys_latency - 1] & ~wrdata_en[cwl_sys_latency]) - self.comb += dqs_pattern.postamble.eq(wrdata_en[cwl_sys_latency + 1] & ~wrdata_en[cwl_sys_latency]) + self.comb += dqs_pattern.preamble.eq( wrdata_en.taps[dq_latency - 1] & ~wrdata_en.taps[dq_latency]) + self.comb += dqs_pattern.postamble.eq(wrdata_en.taps[dq_latency + 1] & ~wrdata_en.taps[dq_latency]) # Xilinx Virtex7 (S7DDRPHY with odelay) ------------------------------------------------------------ diff --git a/litedram/phy/usddrphy.py b/litedram/phy/usddrphy.py index 0e08087..6e52a3c 100644 --- a/litedram/phy/usddrphy.py +++ b/litedram/phy/usddrphy.py @@ -425,33 +425,37 @@ class USDDRPHY(Module, AutoCSR): self.comb += dfi.phases[n//2].rddata[n%2*databits+i].eq(dq_bitslip.o[n]) # Read Control Path ------------------------------------------------------------------------ - # Creates a shift register of read commands coming from the DFI interface. This shift register - # is used to indicate to the DFI interface that the read data is valid. + # Creates a delay line of read commands coming from the DFI interface. The output is used to + # signal a valid read data to the DFI interface. # # The read data valid is asserted for 1 sys_clk cycle when the data is available on the DFI # interface, the latency is the sum of the OSERDESE3, CAS, ISERDESE3 and Bitslip latencies. - rddata_en = Signal(self.settings.read_latency) - rddata_en_last = Signal.like(rddata_en) - self.comb += rddata_en.eq(Cat(reduce(or_, [dfi.phases[i].rddata_en for i in range(nphases)]), rddata_en_last)) - self.sync += rddata_en_last.eq(rddata_en) - self.sync += [phase.rddata_valid.eq(rddata_en[-1] | self._wlevel_en.storage) for phase in dfi.phases] + rddata_en = TappedDelayLine( + signal = reduce(or_, [dfi.phases[i].rddata_en for i in range(nphases)]), + ntaps = self.settings.read_latency + ) + self.submodules += rddata_en + + self.sync += [phase.rddata_valid.eq(rddata_en.output | self._wlevel_en.storage) for phase in dfi.phases] # Write Control Path ----------------------------------------------------------------------- - # Creates a shift register of write commands coming from the DFI interface. This shift register - # is used to control DQ/DQS tristates. - wrdata_en = Signal(cwl_sys_latency + 2) - wrdata_en_last = Signal.like(wrdata_en) - self.comb += wrdata_en.eq(Cat(reduce(or_, [dfi.phases[i].wrdata_en for i in range(nphases)]), wrdata_en_last)) - self.sync += wrdata_en_last.eq(wrdata_en) - self.comb += dq_oe.eq(wrdata_en[cwl_sys_latency]) + # Create a delay line of write commands coming from the DFI interface. This taps are used to + # control DQ/DQS tristates. + wrdata_en = TappedDelayLine( + signal = reduce(or_, [dfi.phases[i].wrdata_en for i in range(nphases)]), + ntaps = cwl_sys_latency + 2 + ) + self.submodules += wrdata_en + + self.comb += dq_oe.eq(wrdata_en.taps[cwl_sys_latency]) self.comb += If(self._wlevel_en.storage, dqs_oe.eq(1)).Else(dqs_oe.eq(dq_oe)) # Write DQS Postamble/Preamble Control Path ------------------------------------------------ # Generates DQS Preamble 1 cycle before the first write and Postamble 1 cycle after the last # write. During writes, DQS tristate is configured as output for at least 3 sys_clk cycles: # 1 for Preamble, 1 for the Write and 1 for the Postamble. - self.comb += dqs_pattern.preamble.eq( wrdata_en[cwl_sys_latency - 1] & ~wrdata_en[cwl_sys_latency]) - self.comb += dqs_pattern.postamble.eq(wrdata_en[cwl_sys_latency + 1] & ~wrdata_en[cwl_sys_latency]) + self.comb += dqs_pattern.preamble.eq( wrdata_en.taps[cwl_sys_latency - 1] & ~wrdata_en.taps[cwl_sys_latency]) + self.comb += dqs_pattern.postamble.eq(wrdata_en.taps[cwl_sys_latency + 1] & ~wrdata_en.taps[cwl_sys_latency]) # Xilinx Ultrascale Plus DDR3/DDR4 PHY -------------------------------------------------------------