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IDELAYCTRL ignored by VPR #1207

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acomodi opened this issue Dec 6, 2019 · 15 comments
Closed

IDELAYCTRL ignored by VPR #1207

acomodi opened this issue Dec 6, 2019 · 15 comments

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@acomodi
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acomodi commented Dec 6, 2019

The current LiteX design instantiates the IDELAYCTRL with inputs only. This causes VPR to ignore the relative nets.

By driving the output signal (RDY) to logic, VPR fails to route due to some issues with the rr_graph, ending in an unroutable situation:

# Routing
  RR Graph Nodes: 1288326
  RR Graph Edges: 7938537
Confirming router algorithm: TIMING_DRIVEN.
---- ------ ------- ---- ------- ------- ------- ----------------- --------------- -------- ---------- ---------- ---------- ---------- --------
Iter   Time    pres  BBs    Heap  Re-Rtd  Re-Rtd Overused RR Nodes      Wirelength      CPD       sTNS       sWNS       hTNS       hWNS Est Succ
      (sec)     fac Updt    push    Nets   Conns                                       (ns)       (ns)       (ns)       (ns)       (ns)     Iter
---- ------ ------- ---- ------- ------- ------- ----------------- --------------- -------- ---------- ---------- ---------- ---------- --------
Warning 186: No routing path for connection to sink_rr 245847, retrying with full device bounding box
Warning 187: No routing path for connection to sink_rr 551334, retrying with full device bounding box
Cannot route from BLK-TL-HCLK_IOI3.HCLK_IOI_IDELAYCTRL_RDY[0] (RR node: 501707 type: SOURCE location: (2,133) class: 3 capacity: 1) to BLK-TL-SLICEL.A2[0] (RR node: 551334 type: SINK location: (12,153) class: 1 capacity: 1) -- no possible path
Failed to route connection from 'serdes_test.idelayctrl' to '$auto$alumacc.cc:485:replace_alu$51.slice[0].carry4_1st_full' for net 'serdes_test.RDY' (#76)
Routing failed.
# Routing took 0.36 seconds (max_rss 2351.8 MiB, delta_rss +0.0 MiB)
Circuit is unroutable with a channel width factor of 500.
VPR failed to implement circuit

the rr_graph_walk tool did not find a possible route between the SOURCE and SINK nodes
@litghost
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I took a look at Vivado, and the path from IDELAYCTRL.RDY is relatively short. It must be a graph import bug or something.

@litghost
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@acomodi Have you create an upstream VTR issue on this problem yet?

@acomodi
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acomodi commented Dec 10, 2019

Not yet, I can open it right now.

@litghost
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litghost commented Dec 10, 2019 •
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Not yet, I can open it right now.

To be clear, the issue is VPR not pruning BELs with inputs and no outputs. The failure to route issue is a graph issue as a result of an issue in the symbiflow-arch-defs graph import.

@litghost
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@acomodi : I just remembered:

  --sweep_dangling_blocks {on, off}
                    Controls whether dangling blocks are removed from the netlist (Default: on)

Try turning off sweep_dangling_blocks. This will leave IDELAYCTRL in place, even in the absence of the RDY signal working

@acomodi
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acomodi commented Dec 10, 2019

Right, I think I had already tried this, but I need to double-check.

@acomodi
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acomodi commented Dec 10, 2019 

  VCC          : 2
  SYN-VCC      : 2
  GND          : 1
  SYN-GND      : 1
  IOB33S       : 5
  BLK-TL-IOPAD_S : 5
  BLK-TL-HCLK_IOI3 : 1
  REG_FDSE_or_FDRE : 24
  BLK-TL-IOPAD : 10
  BLUT         : 1
  C5LUT        : 3
  B5LUT        : 1
  CEUSEDMUX    : 8
  BLK-TL-SLICEL : 6
  BLK-TL-PLLE2_ADV : 1
  SRUSEDMUX    : 8
  SLICE_FF     : 8
  CARRY4_VPR   : 6
  IDELAYE2     : 1
  CE_VCC       : 32
  IOB33_MODES  : 20
  FF_FDSE_or_FDRE : 8
  IDELAYCTRL   : 1
  SLICEL0      : 6
  SLICEM_MODES : 2
  OSERDESE2    : 1
  IOBUF_VPR    : 1
  C_DRAM       : 2
  COMMON_LUT_AND_F78MUX : 1
  FDRE         : 32
  BLK-TL-CLK_BUFG_BOT_R : 1
  PLLE2_ADV    : 1
  outpad       : 10
  inpad        : 11
  ILOGICE3     : 1
  OLOGICE3     : 1
  SR_GND       : 32
  SLICEM       : 2
  A5LUT        : 3
  B_DRAM       : 1
  BLK-TL-SLICEM : 2
  ALUT         : 3
  IOB33M       : 5
  BUFGCTRL1    : 1
  CLUT         : 2
  BUFGCTRL10   : 1
  BLK-TL-IOPAD_M : 5
  COMMON_SLICE : 8
  A_DRAM       : 2
  ISERDESE2    : 1
  lut          : 7
  BUFGCTRL0    : 1
  BUFGCTRL_VPR : 4
  IOB33        : 10
  BUFGCTRL11   : 1


        EMPTY: # blocks: 0, average # input + clock pins used: 0, average # output pins used: 0
        BLK-TL-SLICEL: # blocks: 6, average # input + clock pins used: 13.3333, average # output pins used: 8.5
        BLK-TL-SLICEM: # blocks: 2, average # input + clock pins used: 10, average # output pins used: 6.5
        BLK-TL-BRAM_L: # blocks: 0, average # input + clock pins used: 0, average # output pins used: 0
        BLK-TL-IOPAD: # blocks: 10, average # input + clock pins used: 4.1, average # output pins used: 1.3
        BLK-TL-IOPAD_M: # blocks: 5, average # input + clock pins used: 0.6, average # output pins used: 0.4
        BLK-TL-IOPAD_S: # blocks: 5, average # input + clock pins used: 0.4, average # output pins used: 0.6
        BLK-TL-CLK_BUFG_BOT_R: # blocks: 1, average # input + clock pins used: 32, average # output pins used: 4
        BLK-TL-CLK_BUFG_TOP_R: # blocks: 0, average # input + clock pins used: 0, average # output pins used: 0
        BLK-TL-PLLE2_ADV: # blocks: 1, average # input + clock pins used: 32, average # output pins used: 3
        BLK-TL-HCLK_IOI3: # blocks: 1, average # input + clock pins used: 1, average # output pins used: 0
        SYN-VCC: # blocks: 2, average # input + clock pins used: 0, average # output pins used: 0.5
        SYN-GND: # blocks: 1, average # input + clock pins used: 0, average # output pins used: 1
Absorbed logical nets 73 out of 164 nets, 91 nets not absorbed.
FPGA sized to 150 x 162 (xc7a50t-bottom-test)
Device Utilization: 0.00 (target 1.00)
        Block Utilization: 0.00 Type: BLK-TL-SLICEL
        Block Utilization: 0.00 Type: BLK-TL-SLICEM
        Block Utilization: 0.10 Type: BLK-TL-IOPAD
        Block Utilization: 0.10 Type: BLK-TL-IOPAD_M
        Block Utilization: 0.10 Type: BLK-TL-IOPAD_S
        Block Utilization: 1.00 Type: BLK-TL-CLK_BUFG_BOT_R
        Block Utilization: 0.00 Type: BLK-TL-CLK_BUFG_TOP_R
        Block Utilization: 0.50 Type: BLK-TL-PLLE2_ADV
        Block Utilization: 0.50 Type: BLK-TL-HCLK_IOI3
        Block Utilization: 2.00 Type: SYN-VCC
        Block Utilization: 1.00 Type: SYN-GND

# Packing took 0.51 seconds (max_rss 39.7 MiB, delta_rss +0.0 MiB)
Error 1:
Type: Other
File: /tmp/really-really-really-really-really-really-really-really-really-really-really-really-really-long-path/conda/conda-bld/vtr_1575656400987/work/vpr/src/pack/pack.cpp
Line: 180
Message: Failed to find device which satisifies resource requirements required: BLK-TL-SLICEL: 6, BLK-TL-SLICEM: 2, BLK-TL-IOPAD: 10, BLK-TL-IOPAD_M: 5, BLK-TL-IOPAD_S: 5, BLK-TL-CLK_BUFG_BOT_R: 1, BLK-TL-CLK_BUFG_TOP_R: 0, BLK-TL-PLLE2_ADV: 1, BLK-TL-HCLK_IOI3: 1, SYN-VCC: 2, SYN-GND: 1 (available BLK-TL-SLICEL: 2754, BLK-TL-SLICEM: 867, BLK-TL-IOPAD: 102, BLK-TL-IOPAD_M: 48, BLK-TL-IOPAD_S: 48, BLK-TL-CLK_BUFG_BOT_R: 1, BLK-TL-CLK_BUFG_TOP_R: 1, BLK-TL-PLLE2_ADV: 2, BLK-TL-HCLK_IOI3: 2, SYN-VCC: 1, SYN-GND: 1)
The entire flow of VPR took 0.79 seconds (max_rss 39.7 MiB)

@litghost IDELAYCTRL is there, but VPR failed on VCC blocks. It seems there are too many of them packed, therefore VPR cannot find a suitable device

@litghost
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Maybe we can change the sweep logic to only sweep if there are 0 inputs and 0 outputs? That second VCC is likely totally disconnected?

@acomodi
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acomodi commented Dec 10, 2019

I'll look into that

@acomodi
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acomodi commented Dec 10, 2019

@litghost I believe is easily doable actually, the sweeping mechanism checks only if the block has no outputs. I'll change, that, make a wip branch if it works, and integrate it.

@litghost
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@litghost I believe is easily doable actually, the sweeping mechanism checks only if the block has no outputs. I'll change, that, make a wip branch if it works, and integrate it.

Before you do all that, make sure it fixes our immediate issue.

@acomodi
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acomodi commented Dec 10, 2019

Sure

@litghost
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I've identified a bug in the routing import that will prevent both IDELAYCTRL RST and RDY from being connected to the graph. I'm looking into a fix.

@litghost
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I've identified a bug in the routing import that will prevent both IDELAYCTRL RST and RDY from being connected to the graph. I'm looking into a fix.

I've isolated the issue to be an error in the aliveness check.

@acomodi
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acomodi commented Dec 8, 2020

The IDELAYCTRL can now be correctly placed and routed, closing this issue.

Fixing PRs:

@acomodi acomodi closed this as completed Dec 8, 2020
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