open-source-silicon.dev

If we get violations that are very small, can we ignore them? What is the limit?

I’ll defer to <@U01634FH82K> on the significance of violations.  how large are they?  setup or hold?

<@U01HBEED5T8> could you upload your example here pls?

with the new base.sdc script I'm not getting hold or setup violations.
I'm still getting max slew and max capacitance.
I don't know how bad are they.

or_sta_wrapped_hack_soc_MPW2.log

Some sample values:
```max slew
Pin                                    Limit    Slew   Slack
------------------------------------------------------------
clkbuf_leaf_8_wb_clk_i/A                1.50    2.09   -0.59 (VIOLATED)
clkbuf_leaf_9_wb_clk_i/A                1.50    2.09   -0.59 (VIOLATED)


max capacitance
Pin                                    Limit     Cap   Slack
------------------------------------------------------------
clkbuf_2_2_0_wb_clk_i/X                 0.13    0.18   -0.05 (VIOLATED)
clkbuf_2_1_0_wb_clk_i/X                 0.13    0.17   -0.04 (VIOLATED)
clkbuf_2_3_0_wb_clk_i/X                 0.13    0.16   -0.03 (VIOLATED)```


<@U016HSAA3RQ> <@U01634FH82K> any ideas on this please?

<@U0172QZ342D> the timing closure doc has the answers. Hold violations cannot be tolerated as a single hold vio may render the whole chip non-functional. For setup vios, it is your call. If you cannot fix setup violations you can just extend the clock period if your design does not have a hard requirement for the clock frequency 

These ^^ aren't setup or hold. But I think you already answered about slew and capacitance.

What I think we're missing is understanding what the controls actually do and the range of their vales

<https://skywater-pdk.slack.com/archives/C02K4RD241Y/p1635873241075400?thread_ts=1635445298.049300&amp;cid=C02K4RD241Y|https://skywater-pdk.slack.com/archives/C02K4RD241Y/p1635873241075400?thread_ts=1635445298.049300&amp;cid=C02K4RD241Y>

I will make a pr on the docs to add this info

<https://github.com/The-OpenROAD-Project/OpenLane/pull/691>

<@U0172QZ342D> It is already in the document. I think you missed it somehow. Also, OL docs have description of all variables

maybe I'm missing the docs. Can you post me a link to the OL docs that describe PL_RESIZER_HOLD_SLACK_MARGIN?

if you read the introductory section you will get what it means.

The document has to be read as a whole. Unfortunately, each section is not self contained.

I've made a couple of suggestions. For me the key understanding was to know that the units where time. I'm actually still guessing it's ns. So a confirmation of that would be great.

Sorry for the confusion. I will check them out and make things more clear

no problem, it 's probably totally obvious to you!

but for a lot of us 'slack margin' doesn't necessarily mean adding ns to the margin. A lot of the parameters are % for example

Agreed. I will ask OL doc maintainer to clarify the unit for each variable

Thanks. Just let me know if you have more questions