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I have not really used the openlane flow yet, but I assume it would be possible to generate a new le...
# openlane
w
I have not really used the openlane flow yet, but I assume it would be possible to generate a new lef file or whatever tells the pnr tool where to route things that excludes the areas containing my analog design and then just have it route inside that?
h
Openlane is quite straightforward. You just need the right configuration. You can make your design as a macro and Openlane/openroad can place it and connect it to the IOs. However, we are currently facing the issue with the lef generation. Some versions of our macro (with the lef generated by Magic) can't be route with TritonRoute. I don't know if others face this problem.
w
I sorta have the inverse problem. I have an already routed chip and want to route a digital design in the remaining areas / IOs
h
I think that you can use openlane to generate the layout for the digital module and then put it in your chip.
m
Maybe you can team up with @Amro Tork. He needs a bit of space a d has openlane experience
a
Hi @Hieu Bui
I have space
But have constraints on pins
How many pins?
Or we could use @Matt Venn multi project to create a new multi project
@Matt Venn Could you advise how to use this multi project repo?
I can wrap a new multi project just like yours
h
Hi Amro Tork, I am trying to finish our project. It can pass precheck already and it is quite big with two 4k SRAMs. However, we got something very weird when integrating a customized cell into openlane.
w
One of my friends, @Peter Schmidt-Nielsen was hoping to put something on the extra space and already has something that routes but we dont know how to create a custom wrapper to have it route in instead of the whole chip area
a
@Weston Braun Is yours Analog?
w
yah.
a
@Hieu Bui How big is your design? Dimensions ?
w
I used all the pins
a
But you have the digital pins free?
w
Is there a way to disable to wishbone bus from the management processor? Or can a bad design on the bus lock the chip?
a
Not sure about that
m
Only writes to 0x30 will get passed thru
w
The only constraint here is that I cant risk the rest of the functionality.
m
So ignore it
w
So there is no way that a bad design on the digital lines can lock the chip?
m
@Amro Tork the multi tools are fairly well documented now and there are lots of example sub projects
w
this is my layout
I would need to route the power from one of the 1V8 pins for you
I am using none of the digital IO
a
Could I place my osc with you?
@Weston Braun
Digital only
@Matt Venn thanks . I’ll take a look at it now
w
If you can figure out a way to route a drc clean design that does not overlap with any of my chip area. I assume we can OR the two designs together or something
m
What do you mean lock the chip?
a
@Weston Braun yes I can
w
I need the management core to configure the IO states. If a bad digital design locks up the managment core I will be very sad
a
Where is your repo?
Did you do fill?
w
Stanford secured tapeout slots through the Chipignite program, so this is actually taping out. So adding a digital design is basically all risk no reward for me
they do the fill after submission, no? This passes the local prechecks (but not the online one because that uses an outdated magic version)
a
Cool
@Weston Braun no worries
w
I need to integrate one last thing connecting to the last IO. So just assume constant clearance from the edges. And I need to route a power rail for you from the external 1V8 pin
Also, if you figure this out, you need to help @Peter Schmidt-Nielsen get his design into the digital logic area too. I assume your design is small-ish? His is too.
He only needs the LA bus
and not all the pins
m
I can't think of any way that could happen
w
I can ask Tim Edwards tommor
A tapeout is like 10k or whatever, I dont want to screw it up
a
Tell @Peter Schmidt-Nielsen to contact me
w
a
Oh
Is that an LDO?
w
its a current mode buck converter
a
What’s your output voltage (
1.8?
w
1.8V
I also lowkey want some digital logic on the chip because then I can power it from the buck converter
a
Did you pass corners?
And everything?
w
I am having extraction issues for parasitics, but the initial design passes all process and load corner cases
a
Nice
Glad to see that rolling
Are you sharing the design spice and schematics?
w
Yah, the repo is a mess right now
I am migrating everything over, but its all FOSS
a
Nice
Thanks Weston
p
@Amro Tork Hello, yes, I'd love to get some help on this.
a
HI @Peter Schmidt-Nielsen
p
I have some Verilog, and I assume it's relatively synthesizable (I only ever 
always @(posedge clock)
, never use 
#
, or 
initial
, and whatnot, so I assume it should be able to synthesize a single big block of combinational logic and set of registers and that's it.) but I haven't been able to synthesize it with the 
caravel_user_project
stuff for silly reasons.
a
Is yours analog or digital?
p
Completely digital.
a
Great
I need the GDS from Openlane not form caravel_user_project.
I'm not able to Synthesize from caravel_user_project as well.
Ignore it for now.
p
Aha, got it.
How have you been building said GDS? I'd be happy to try to build it. I can also put my Verilog up somewhere.
I've just been doing 
make user_project_wrapper
and 
make user_proj_example
.
a
@Peter Schmidt-Nielsen You need to use Openlane RTL to GDS flow.
Assuming that your Verilog is RTL.
p
Okay, got it. I think I have all the openlane and PDK stuff installed, although I don't know how to invoke it directly. I can launch into trying to do this right now.
By "your Verilog is RTL" you mean I never request FETs or gates and stuff, and only ever 
<=
into registers?
a
I don't think you go to FETs.
Very rarely Gates.
p
If so, yes, 100% of what I've got is various `<=`s inside of `case`s, `if`s in 
always @(posedge clock)
blocks. If I were manually implementing this I'd just have a single big combinational block and a bunch of flip flops, and that's it. That's all I want it to synthesize.
a
Here is the steps for openlane in nutshell:
1. Clone openlane latest version. 2. cd openlane 3. make openlane 4. make pdk 5. make test 6. create a new folder under designs with your design name "peter_chip" for example. 7. Copy one of the config.tcl from one of the other designs in the "designs" folder to yours. 8. Modify the config.tcl as needed. You will need to read openlane documentation for that. 9. Copy your verilog into the your "peter_chip" folder. 10. make mount 11. ./flow.tcl -design peter_chip -tag first_run
Hopefully after all of that you don't get any errors through the process.
p
Okay, sweet, let me try that literally right now.
@Amro Tork Okay, this is working great for me, what you suggested synthesized my design and spat out a GDS file! As a next step, do you know how I might be able to integrate this with what Weston has? In particular, I just need to get: power, clock, and a handful of the logic analyzer lines. Do I need to make a custom LEF for that?
I got this sort of thing out, and a GDS file. I have no idea where it hooked up the ports for my module. I presume I need to separately specify where I need that to go. I have no idea how to hook that up with the Caravel harness' RISC-V core, and how to integrate that with Weston's GDS file.
I'm currently looking at the LEF files that come with 
caravel_user_project
, they seem promising, although I don't know how to make openlane route to them, and I especially don't know how to make it not do anything in Weston's area.
m
after you have the separate hardened macros in gds and lef, then you can instantiate and wire them up in user_project_wrapper
then you choose where they are put in openlane/user_project_wrapper/macro.cfg to set x and y
then you run make user_project_wrapper and it will try to do the routing and PDN
p
@Matt Venn Got it, thanks. Are the GDS file and LEF file that I got by default via 
./flow.tcl -design mything -tag run1
in 
designs/snproc/runs/run1/results/magic/mything.gds
and 
designs/snproc/runs/run1/results/magic/mything.lef
the hardened macro to which you refer?
m
yes
so those go in the top level gds and lef directories
then look at how the wrapper instances mprj and replace that with your macro
🙏 1
p
Okay, sweet, thanks so much, I'm going to check this out right now, I'll probably have a bunch of questions.
@Matt Venn Okay, very cool, I see in that 
macro.cfg
file you mention it gives x and y, and sure enough, those seem to be exactly where the user project was placed in 
openlane/user_project_wrapper/runs/user_project_wrapper/results/magic/user_project_wrapper.gds
. I put the 
.lef
and 
.gds
into the top-level 
lef/
and 
gds/
directories you mentioned. I'm trying to swap the entry in 
macro.cfg
out for my macro, but the Python script is saying 
AssertionError: ('Macros not found:', {'snproc': ['1175000', '1690000', 'N']})
. I tried adding my lef and gds files explicitly in the 
config.tcl
under 
EXTRA_LEFS
and 
EXTRA_GDS_FILES
, but to no avail.
Am I missing something super simple?
m
Have you instantiated it in user project wrapper?
p
I suspect not, but I'm not sure how. Do you mean adding something to 
verilog/rtl/user_project_wrapper.v
? Right now I see 
user_proj_example mprj ( ... );
there at the end, am I adding something comparable, but that matches up with the defined pins in the 
.lef
file I generated?
@Matt Venn I'm still unsure of how merging this with Weston's stuff will eventually work. Like, if I get the 
user_project_wrapper
producing a GDS file with my stuff nicely routed to the various project wrapper pins I assume it'll still want to fill the entire space, and thus won't be immediately mergable with Weston's GDS file. Do you have thoughts on this? "Nope" is, of course, a totally fine answer.
@Amro Tork Do you know how to get power and clock signals into the block I synthesized? I think I'm pretty much ready with what I want to merge into Weston's GDS. Were you also going to merge something in?
a
@Peter Schmidt-Nielsen I’m not an expert on Openlane
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