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Resizer unable to optimize fanout for GF180 PDK #2339

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vijayank88 opened this issue Oct 6, 2022 · 26 comments · Fixed by google/globalfoundries-pdk-libs-gf180mcu_fd_sc_mcu7t5v0#22 or google/globalfoundries-pdk-libs-gf180mcu_fd_sc_mcu9t5v0#19
Closed

Resizer unable to optimize fanout for GF180 PDK #2339

vijayank88 opened this issue Oct 6, 2022 · 26 comments · Fixed by google/globalfoundries-pdk-libs-gf180mcu_fd_sc_mcu7t5v0#22 or google/globalfoundries-pdk-libs-gf180mcu_fd_sc_mcu9t5v0#19
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@QuantamHD

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@vijayank88
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Testing aes design with GF180 PDK through OpenLane flow.
Using OpenROAD 4174c3ad802d2ac1d04d387d2c4b883903f6647e

resizer.log

===========================================================================
report_checks -path_delay max (Setup)
============================================================================
Startpoint: reset_n (input port clocked by clk)
Endpoint: _38075_ (recovery check against rising-edge clock clk)
Path Group: **async_default**
Path Type: max

Fanout     Cap    Slew   Delay    Time   Description
-----------------------------------------------------------------------------
                  0.15    0.00    0.00   clock clk (rise edge)
                          0.00    0.00   clock network delay (ideal)
                         10.00   10.00 ^ input external delay
                  1.15    0.64   10.64 ^ reset_n (in)
     1    0.05                           reset_n (net)
                  1.15    0.00   10.64 ^ input10/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  0.83    0.72   11.36 ^ input10/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
    86    0.72                           net10 (net)
                  0.87    0.09   11.45 ^ load_slew88/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  1.56    1.10   12.55 ^ load_slew88/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   179    1.36                           net88 (net)
                  1.58    0.10   12.65 ^ load_slew87/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  2.09    1.39   14.04 ^ load_slew87/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   236    1.87                           net87 (net)
                  2.12    0.14   14.17 ^ load_slew85/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  2.09    1.49   15.66 ^ load_slew85/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   236    1.80                           net85 (net)
                  2.11    0.12   15.77 ^ load_slew84/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  1.62    1.19   16.96 ^ load_slew84/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   185    1.40                           net84 (net)
                  1.63    0.04   17.00 ^ load_slew83/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  1.77    1.23   18.23 ^ load_slew83/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   210    1.55                           net83 (net)
                  1.90    0.28   18.51 ^ _38075_/RN (gf180mcu_fd_sc_mcu7t5v0__dffrnq_1)
                                 18.51   data arrival time

                  0.15   50.00   50.00   clock clk (rise edge)
                          0.00   50.00   clock network delay (ideal)
                         -0.25   49.75   clock uncertainty
                          0.00   49.75   clock reconvergence pessimism
                                 49.75 ^ _38075_/CLK (gf180mcu_fd_sc_mcu7t5v0__dffrnq_1)
                          0.00   49.75   library recovery time
                                 49.75   data required time
-----------------------------------------------------------------------------
                                 49.75   data required time
                                -18.51   data arrival time
-----------------------------------------------------------------------------
                                 31.24   slack (MET)

Test case:
issue_reproducible.zip
@maliberty
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Please run this with the latest OR and package a test case from that: incompatible database schema revision

@maliberty
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I don't see any max_fanout specified in gf180

@antonblanchard
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The SDC file has a fanout limit:

set_max_fanout 8.0000 [current_design]

but the liberty file is missing:

  default_fanout_load : 1.0000000000;

Same problem as we had on sky130.

@maliberty
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@proppy @QuantamHD PDK issue...

@QuantamHD
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Looking now.

@maliberty
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@louiic see the note from Anton

@QuantamHD
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@maliberty @antonblanchard I don't see a default_fanout_load in the NDA'd liberty. So we'll need to add it.

@QuantamHD
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What is a sensible default?

@antonblanchard
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What is a sensible default?

I think 1, that's what we changed the sky130 PDK to use in RTimothyEdwards/open_pdks@86f9b0c

@louiic
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louiic commented Oct 6, 2022 via email

@antonblanchard
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antonblanchard commented Oct 6, 2022 •
edited
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Ethan, I tried setting default_max_fanout in .LIB … did not help.

Works for me. Are you sure your SDC has a set_max_fanout statement and your liberty file has default_fanout_load : 1?

baseline:

Startpoint: reset_n (input port clocked by clk)
Endpoint: _38075_ (recovery check against rising-edge clock clk)
Path Group: **async_default**
Path Type: max

Fanout     Cap    Slew   Delay    Time   Description
-----------------------------------------------------------------------------
                  0.15    0.00    0.00   clock clk (rise edge)
                          0.00    0.00   clock network delay (ideal)
                         10.00   10.00 ^ input external delay
                  0.19    0.07   10.07 ^ reset_n (in)
     1    0.00                           reset_n (net)
                  0.19    0.00   10.07 ^ input53/I (gf180mcu_fd_sc_mcu7t5v0__buf_2)
                  0.57    0.55   10.62 ^ input53/Z (gf180mcu_fd_sc_mcu7t5v0__buf_2)
     1    0.05                           net98 (net)
                  0.57    0.00   10.62 ^ input10/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  0.84    0.68   11.30 ^ input10/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
    86    0.72                           net10 (net)
                  0.87    0.09   11.39 ^ repeater88/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  1.56    1.10   12.49 ^ repeater88/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   179    1.36                           net88 (net)
                  1.58    0.10   12.59 ^ repeater87/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  2.09    1.39   13.98 ^ repeater87/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   236    1.87                           net87 (net)
                  2.12    0.14   14.11 ^ repeater85/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  2.09    1.49   15.60 ^ repeater85/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   236    1.80                           net85 (net)
                  2.11    0.12   15.72 ^ repeater84/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  1.62    1.19   16.91 ^ repeater84/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   185    1.40                           net84 (net)
                  1.63    0.04   16.94 ^ repeater83/I (gf180mcu_fd_sc_mcu7t5v0__buf_20)
                  1.77    1.23   18.17 ^ repeater83/Z (gf180mcu_fd_sc_mcu7t5v0__buf_20)
   210    1.55                           net83 (net)
                  1.90    0.28   18.45 ^ _38075_/RN (gf180mcu_fd_sc_mcu7t5v0__dffrnq_1)
                                 18.45   data arrival time

                  0.15   50.00   50.00   clock clk (rise edge)
                          0.00   50.00   clock network delay (ideal)
                         -0.25   49.75   clock uncertainty
                          0.00   49.75   clock reconvergence pessimism
                                 49.75 ^ _38075_/CLK (gf180mcu_fd_sc_mcu7t5v0__dffrnq_1)
                          0.00   49.75   library recovery time
                                 49.75   data required time
-----------------------------------------------------------------------------
                                 49.75   data required time
                                -18.45   data arrival time
-----------------------------------------------------------------------------
                                 31.30   slack (MET)

With the fix:

Startpoint: reset_n (input port clocked by clk)
Endpoint: _37688_ (recovery check against rising-edge clock clk)
Path Group: **async_default**
Path Type: max

Fanout     Cap    Slew   Delay    Time   Description
-----------------------------------------------------------------------------
                  0.15    0.00    0.00   clock clk (rise edge)
                          0.00    0.00   clock network delay (ideal)
                         10.00   10.00 ^ input external delay
                  0.16    0.05   10.05 ^ reset_n (in)
     1    0.00                           reset_n (net)
                  0.16    0.00   10.05 ^ input53/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.29    0.37   10.42 ^ input53/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     1    0.01                           net98 (net)
                  0.29    0.00   10.42 ^ input10/I (gf180mcu_fd_sc_mcu7t5v0__buf_4)
                  0.16    0.29   10.72 ^ input10/Z (gf180mcu_fd_sc_mcu7t5v0__buf_4)
     3    0.02                           net10 (net)
                  0.16    0.00   10.72 ^ fanout611/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.61    0.58   11.30 ^ fanout611/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     4    0.02                           net656 (net)
                  0.61    0.00   11.30 ^ fanout610/I (gf180mcu_fd_sc_mcu7t5v0__buf_2)
                  0.65    0.66   11.95 ^ fanout610/Z (gf180mcu_fd_sc_mcu7t5v0__buf_2)
     7    0.05                           net655 (net)
                  0.65    0.00   11.95 ^ repeater88/I (gf180mcu_fd_sc_mcu7t5v0__buf_4)
                  0.14    0.31   12.27 ^ repeater88/Z (gf180mcu_fd_sc_mcu7t5v0__buf_4)
     2    0.01                           net88 (net)
                  0.14    0.00   12.27 ^ fanout535/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.56    0.54   12.80 ^ fanout535/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     4    0.02                           net580 (net)
                  0.56    0.00   12.80 ^ fanout525/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.74    0.72   13.52 ^ fanout525/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     4    0.03                           net570 (net)
                  0.74    0.00   13.52 ^ fanout524/I (gf180mcu_fd_sc_mcu7t5v0__buf_2)
                  0.69    0.70   14.21 ^ fanout524/Z (gf180mcu_fd_sc_mcu7t5v0__buf_2)
     8    0.06                           net569 (net)
                  0.69    0.00   14.22 ^ repeater87/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.16    0.37   14.58 ^ repeater87/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     1    0.00                           net87 (net)
                  0.16    0.00   14.58 ^ fanout412/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.76    0.67   15.25 ^ fanout412/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     5    0.03                           net457 (net)
                  0.76    0.00   15.26 ^ fanout400/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.69    0.71   15.96 ^ fanout400/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     4    0.03                           net445 (net)
                  0.69    0.00   15.96 ^ fanout399/I (gf180mcu_fd_sc_mcu7t5v0__buf_3)
                  0.59    0.69   16.66 ^ fanout399/Z (gf180mcu_fd_sc_mcu7t5v0__buf_3)
     8    0.07                           net444 (net)
                  0.59    0.00   16.66 ^ repeater85/I (gf180mcu_fd_sc_mcu7t5v0__buf_8)
                  0.13    0.30   16.97 ^ repeater85/Z (gf180mcu_fd_sc_mcu7t5v0__buf_8)
     3    0.02                           net85 (net)
                  0.13    0.00   16.97 ^ fanout262/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.52    0.51   17.48 ^ fanout262/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     5    0.02                           net307 (net)
                  0.52    0.00   17.48 ^ fanout243/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.77    0.73   18.21 ^ fanout243/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     5    0.03                           net288 (net)
                  0.77    0.00   18.21 ^ fanout239/I (gf180mcu_fd_sc_mcu7t5v0__buf_2)
                  0.69    0.70   18.91 ^ fanout239/Z (gf180mcu_fd_sc_mcu7t5v0__buf_2)
     8    0.06                           net284 (net)
                  0.69    0.00   18.91 ^ repeater84/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.16    0.37   19.28 ^ repeater84/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     1    0.00                           net84 (net)
                  0.16    0.00   19.28 ^ fanout191/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.69    0.62   19.90 ^ fanout191/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     4    0.03                           net236 (net)
                  0.69    0.00   19.90 ^ fanout186/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.52    0.61   20.51 ^ fanout186/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     4    0.02                           net231 (net)
                  0.52    0.00   20.51 ^ fanout182/I (gf180mcu_fd_sc_mcu7t5v0__buf_2)
                  0.50    0.56   21.06 ^ fanout182/Z (gf180mcu_fd_sc_mcu7t5v0__buf_2)
     6    0.04                           net227 (net)
                  0.50    0.00   21.06 ^ fanout180/I (gf180mcu_fd_sc_mcu7t5v0__buf_2)
                  0.69    0.67   21.73 ^ fanout180/Z (gf180mcu_fd_sc_mcu7t5v0__buf_2)
     8    0.06                           net225 (net)
                  0.69    0.00   21.73 ^ repeater83/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.18    0.38   22.11 ^ repeater83/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     1    0.00                           net83 (net)
                  0.18    0.00   22.11 ^ fanout157/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_2)
                  0.41    0.52   22.63 ^ fanout157/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_2)
     5    0.03                           net202 (net)
                  0.41    0.00   22.64 ^ fanout132/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.55    0.58   23.22 ^ fanout132/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     4    0.02                           net177 (net)
                  0.55    0.00   23.22 ^ fanout124/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.62    0.64   23.86 ^ fanout124/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     4    0.02                           net169 (net)
                  0.62    0.00   23.86 ^ fanout120/I (gf180mcu_fd_sc_mcu7t5v0__buf_2)
                  0.71    0.70   24.56 ^ fanout120/Z (gf180mcu_fd_sc_mcu7t5v0__buf_2)
     8    0.06                           net165 (net)
                  0.71    0.00   24.56 ^ fanout119/I (gf180mcu_fd_sc_mcu7t5v0__buf_2)
                  0.73    0.72   25.28 ^ fanout119/Z (gf180mcu_fd_sc_mcu7t5v0__buf_2)
     8    0.06                           net164 (net)
                  0.73    0.00   25.28 ^ _37688_/RN (gf180mcu_fd_sc_mcu7t5v0__dffrnq_1)
                                 25.28   data arrival time

                  0.15   50.00   50.00   clock clk (rise edge)
                          0.00   50.00   clock network delay (ideal)
                         -0.25   49.75   clock uncertainty
                          0.00   49.75   clock reconvergence pessimism
                                 49.75 ^ _37688_/CLK (gf180mcu_fd_sc_mcu7t5v0__dffrnq_1)
                          0.33   50.08   library recovery time
                                 50.08   data required time
-----------------------------------------------------------------------------
                                 50.08   data required time
                                -25.28   data arrival time
-----------------------------------------------------------------------------
                                 24.80   slack (MET)

@maliberty
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maliberty commented Oct 6, 2022 •
edited
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@antonblanchard What happens to the area/power with this change? Timing is met either way

@louiic
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louiic commented Oct 6, 2022 via email

@antonblanchard
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@antonblanchard What happens to the area/power with this change? Timing is met either way

I was investigating why the design specified a max fanout, but OpenROAD ignored it. No idea what it does for area/performance.

@vijayank88 what is the issue here? As @maliberty mentions the design makes timing.

@vijayank88
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with gf180 there are slew violations post routing. So just back traced to placement and found fanout issue. so raised this.
max slew violation = 132
max cap violation = 32

@vijayank88
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vijayank88 commented Oct 7, 2022 •
edited
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@antonblanchard
I have updated liberty file as follows:

slew_upper_threshold_pct_fall : 70 ; 
  slew_upper_threshold_pct_rise : 70 ; 
  default_max_fanout : 1.0000000000 ;
  default_fanout_load : 1.0000000000 ;
  nom_process : 1 ;

Still having same fanout issue. Can you share snippet where to update as resolves fanout issue at your end?

@antonblanchard
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@vijayank88 can you be more specific when you talk about "fanout issue"? Do you mean you have slew and capacitance violations when measured after global placement, or do you mean that the SDC fanout constraint is not being obeyed?

I see 0 slew and capacitance violations using your original test case, but I did have to convert your old odb by writing out a def on an old checkout of openroad and reading the def and writing the odb on a more recent one. Perhaps something critical in the odb was lost in the process.

The version of OpenROAD you are using looks to be pretty ancient, can you please recreate on a recent check out?

@vijayank88
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vijayank88 commented Oct 7, 2022 •
edited
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@antonblanchard
Issue is sdc fanout constraint not obeyed.
Latest test case: OpenROAD commit : bf529ad4a22a876d5100e5f3076f151d01dae67c
issue_reproducible.zip

@antonblanchard
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@antonblanchard Issue is sdc fanout constraint not obeyed.

I took your most recent zip, made the following change:

--- ./tmp/synthesis/resizer_gf180mcu_fd_sc_mcu7t5v0__tt_025C_3v30.lib~	2022-10-07 20:23:36.805561983 +1100
+++ ./tmp/synthesis/resizer_gf180mcu_fd_sc_mcu7t5v0__tt_025C_3v30.lib	2022-10-07 20:23:58.070617591 +1100
@@ -23,6 +23,7 @@
   capacitive_load_unit(1, pf);
   pulling_resistance_unit : 1ohm ; 
   leakage_power_unit : 1uW ; 
+  default_fanout_load: 1;
   input_threshold_pct_fall : 50 ; 
   input_threshold_pct_rise : 50 ; 
   output_threshold_pct_fall : 50 ;

And I see it work as expected:

Endpoint: _38616_ (recovery check against rising-edge clock clk)
Path Group: **async_default**
Path Type: max

Fanout     Cap    Slew   Delay    Time   Description
-----------------------------------------------------------------------------
                  0.15    0.00    0.00   clock clk (rise edge)
                          0.00    0.00   clock network delay (ideal)
                         10.00   10.00 ^ input external delay
                  0.16    0.05   10.05 ^ reset_n (in)
     1    0.00                           reset_n (net)
                  0.16    0.00   10.05 ^ input10/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.25    0.34   10.40 ^ input10/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     1    0.01                           net10 (net)
                  0.25    0.00   10.40 ^ fanout546/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_2)
                  0.45    0.56   10.96 ^ fanout546/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_2)
     5    0.03                           net546 (net)
                  0.45    0.01   10.97 ^ fanout388/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.69    0.67   11.64 ^ fanout388/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     4    0.03                           net388 (net)
                  0.69    0.00   11.64 ^ fanout387/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_2)
                  0.45    0.65   12.29 ^ fanout387/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_2)
     5    0.03                           net387 (net)
                  0.45    0.00   12.29 ^ fanout349/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.50    0.56   12.85 ^ fanout349/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     4    0.02                           net349 (net)
                  0.50    0.00   12.85 ^ fanout348/I (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
                  0.52    0.58   13.43 ^ fanout348/Z (gf180mcu_fd_sc_mcu7t5v0__clkbuf_1)
     4    0.02                           net348 (net)
                  0.52    0.00   13.43 ^ fanout347/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.63    0.65   14.07 ^ fanout347/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     4    0.02                           net347 (net)
                  0.63    0.00   14.07 ^ fanout345/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.75    0.73   14.80 ^ fanout345/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     5    0.03                           net345 (net)
                  0.75    0.00   14.80 ^ fanout343/I (gf180mcu_fd_sc_mcu7t5v0__buf_1)
                  0.78    0.74   15.55 ^ fanout343/Z (gf180mcu_fd_sc_mcu7t5v0__buf_1)
     4    0.03                           net343 (net)
                  0.78    0.00   15.55 ^ _38616_/RN (gf180mcu_fd_sc_mcu7t5v0__dffrnq_1)
                                 15.55   data arrival time

                  0.15   50.00   50.00   clock clk (rise edge)
                          0.00   50.00   clock network delay (ideal)
                         -0.25   49.75   clock uncertainty
                          0.00   49.75   clock reconvergence pessimism
                                 49.75 ^ _38616_/CLK (gf180mcu_fd_sc_mcu7t5v0__dffrnq_1)
                          0.32   50.07   library recovery time
                                 50.07   data required time
-----------------------------------------------------------------------------
                                 50.07   data required time
                                -15.55   data arrival time
-----------------------------------------------------------------------------
                                 34.53   slack (MET)

@vijayank88
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@antonblanchard
Thanks. By updating default_fanout_load : 1.0000000000 ; into liberty files resolved fanout issue.
Can you please once verify is any other parameters to be updated in .lib files of GF180 PDK?
We can request @proppy to update this in PDK.

@jjcherry56
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@vijayank88 @louiic @QuantamHD all confused default_max_fanout with default_fanout_load.
Contrary to common sense, fanout is defined by the liberty pin attribute fanout_load, which defaults to
the library attribute default_fanout_load, NOT the connections in the netlist.
If default_fanout_load is 0, the pin is not counted in the fanout of the driver and there can never be fanout violations. We went through this same nonsense with sky130.
As a result of that, opensta warns about this when reading the liberty, but of course no one actually looks at the warnings.

@louiic @vijayank88 it would never make any sense to set default_max_fanout to 1 in the liberty.
That would constrain all gates to only have one load.

@QuantamHD
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@jjcherry56 What modification to the liberty file would you suggest?

@jjcherry56
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The only change required is fixing default_fanout_load to 1

@antonblanchard
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I created google/gf180mcu-pdk#81

QuantamHD added a commit to QuantamHD/globalfoundries-pdk-libs-gf180mcu_fd_sc_mcu7t5v0 that referenced this issue Oct 25, 2022
@QuantamHD
Fixes buffer resizing for PnR tools
e3fa771 
Fixes The-OpenROAD-Project/OpenROAD#2339
@QuantamHD QuantamHD mentioned this issue Oct 25, 2022
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@vijayank88 vijayank88 mentioned this issue Nov 10, 2022
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QuantamHD added a commit to google/globalfoundries-pdk-libs-gf180mcu_fd_sc_mcu9t5v0 that referenced this issue Nov 23, 2022
@QuantamHD
Updates default_fanout_load for the standard cell library
35c8eec 
Fixes The-OpenROAD-Project/OpenROAD#2339

- [x] Tests pass
- [x] Appropriate changes to README are included in PR
@QuantamHD QuantamHD mentioned this issue Nov 23, 2022
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@QuantamHD
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Can we validate that this is fixed with the upstream changes?

@vijayank88
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@QuantamHD With latest PDK this issue got resolved.

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@maliberty @antonblanchard @QuantamHD @jjcherry56 @louiic @vijayank88