Tuesday, 2018-03-27

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ZipCPUxerpi: The github issue has been closed, although I haven't tried the updated version myself (yet)01:20
ZipCPUmithro: I didn't get your comment on the issue tracker.  Care to explain what's so awesome about ABC moving?01:20
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cr1901_modernZipCPU: It means I don't have to deal with Mercurial anymore :)01:37
ZipCPUAhh ... okay.  That wasn't clear from your post ... :)01:38
cr1901_modernZipCPU: My personal opinion does not necessarily reflect mithro's :)01:38
ZipCPUAhm ... okay ... Sorry.01:39
* cr1901_modern told a bad joke :(01:39
ZipCPUWell ... not that so much as ... you've left me confused.01:40
ZipCPUWhen you answered for mithro, I assumed that cr1901_modern and mithro were two pseudoname's for the same person, so I responded as such01:40
ZipCPUNo I feel embarrassed for having made a mistake01:41
cr1901_modernNah, I am not mithro :). Tim's Australian, I'm... well, from NJ01:41
ZipCPUAh, ok01:42
ZipCPUI guess I was just confused.01:42
ZipCPUIt's nearly nighttime in here on the East coast, so ... I'm doing my vesper's and thinking about testing a SPI flash simulator before bed ...01:43
cr1901_modernWhat is a vesper?01:43
* ZipCPU checks the dictionary ...01:44
ZipCPUVesper: evening prayers01:44
cr1901_modernAhhh I see01:45
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promachJust for curiousity, what do you guys think about https://i.imgur.com/JDrAIL0.png ?04:12
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xerpiclifford, thanks for the fast fixes!07:41
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* shapr hops quietly15:10
* ZipCPU wonders if shapr likes "hip hop"15:15
shaprwell, I like hop15:15
shaprhowdy ZipCPU! How you doin?15:15
ZipCPUI spent all yesterday trying to figure out how to reconfigure a Cyclone-V FPGA.15:16
shaprthat does sound frustrating15:16
ZipCPUThe interface that's well documented no longer exists, and Linux doesn't like my attempts at building device tree overlays15:16
ZipCPU(I've never built them before, so ... this is a new thing for me as well.)15:16
shaprnew things are good15:17
ZipCPUWhile device tree overlays are the wave of the future for reconfiguring FPGA's without taking the O/S down, Linux didn't accept any of my attempts.  As a result, I'm fruitless searching the Linux kernel for clues as to what I'm doing wrong.15:17
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shaprsadly, I know nothing about that15:18
ZipCPULol ... yeah, that's my problem: neither do I :P15:18
shaprdid you ask on twitter?15:18
shaprlots of FPGA people connected to you15:18
shaprthat's what I do when I'm stuck on a problem15:19
ZipCPUNo.  I complained on twitter.15:19
shaprI got a good answer when asking whether murmurhash3 or siphash was better for a bloom filter.15:19
daveshahMust say it's a lot easier on a Zynq, you just `cat` the new bitstream into a device node15:20
ZipCPUYou mean like, cat configuration.bin > /dev/fpga0 ?15:20
ZipCPUThat interface has been deprecated in the Linux kernel, and that's part of what I'm struggling with.15:20
awygleDTOs are awesome but they're pretty new, do you have a recent kernel? 4.x?15:20
daveshahYes, that's how I did it when I was doing Zynq stuff. Didn't know it had been deprecated. Have always found device tree stuff a bit of a pain tbh15:21
shaprwhat's better about the device tree?15:22
ZipCPUWell ... the idea is that the device tree captures some of the dependencies required by loading15:25
ZipCPUFor the Cyclone-V part, you need to turn off the bus "bridges" to the FPGA before you can reload the configuration15:25
ZipCPUAnd the device tree is supposed to help encapsulate that process15:25
awygledevice trees are a great idea - describe the PCB to the kernel so it knows what's physically attached - but yes the implementation is a bit hair-pulling15:26
ZipCPUEspecially when it's not well documented.15:26
shaproh, the tree describes what devices are attached to what?15:26
ZipCPUSo, a bit of history ...15:27
awyglei find that Beaglebone has the best documentation for this kind of thing, or did ~1yr ago15:27
ZipCPUDevice trees were invented primarily because of ARM.  ARM was selling a CPU in terms of IP, and every chip maker was adding their own devices to it15:27
ZipCPUTo deal with this, Linus invented the device tree--something that tells Linux what devices are available to it and where they are found in the memory map15:27
daveshahIn general my problem hasn't been the device tree system itself, but the vendor documentation for it15:27
daveshahI agree in theory it is a good idea15:28
ZipCPUdaveshah: What, you've struggled with this as well?15:28
shaprZipCPU: sounds good so far15:28
daveshahVarious previous projects, mostly doing slightly weird stuff on a Zynq15:28
q3kand before DT we had ARM machine/board IDs15:28
awygledevice trees would be easier to use if they were attached to better subsystems.... ;)15:28
daveshahI remember a project I did with the iMX233 using 2.615:28
ZipCPUshapr: So, the next step was a "device tree overlay".  This was supposed to support hardware reconfiguration15:28
daveshahWith a hardcoded C file doing init15:28
awyglei tried to do GPIO stuff recently, that got _complicated_15:28
ZipCPUWith a device tree overlay, you can "add hardware" to  running Linux system, and keep the kernel informed of what's there.15:29
shaprsounds useful?15:29
q3kdaveshah: did that for some OMAPs, that was, uh, fun15:29
ZipCPUshapr: However, the overlay must match the current kernel in enough detail in order to be understood.  That's where I seem to be failing.15:29
q3kand then there's some vendors (*cough* allwinner *cough*) that ship their own clone of DT because why not15:30
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mjo-uk_I think it's the case that not all device tree subsystems support loading stuff dynamically. I hit this problem about a year ago trying to reconfigure the LED subsystem on a Raspberry Pi. So it works if you load it at boot but you can't unload it and load it again on a live system.15:58
ZipCPUmjo-uk_: Thanks for the insight.  This might be my problem.16:01
mjo-uk_ZipCPU: A pleasure. By the way, I've really enjoyed reading your many fine articles about FPGA design. Thank you so much for posting them.16:01
ZipCPUThank you!16:02
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mattvennjust continuing on this DTO thread, recent beaglebone stuff has done away with the dynamic loading of overlays16:59
mattvennit's never worked properly - have to set it up at boot16:59
mattvennthere are some very useful people on the #beagle channel16:59
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janrinzehi people here17:23
janrinzeare there people here who are willing to teach me some tricks on timing analysys?17:24
janrinzehi sorear17:24
awyglejanrinze: unless you are specifically talking about "icetime", i suspect this will not be the most productive channel for you, you may wish to try ##fpga17:30
janrinzeicetime indeed17:30
janrinzeI'm not yet familiar with what it can do for me to find slowest path and such17:31
janrinze    36.556 ns .. 37.145 ns $abc$54082$n2094_117:35
janrinze    37.461 ns .. 38.050 ns $abc$54082$n2085_117:35
janrinze    38.450 ns .. 40.729 ns $abc$54082$n2147_117:35
janrinze    41.108 ns .. 44.657 ns $abc$54082$n3465_117:35
janrinzethis kind of feedback is hard to trace back to something in the verilog.17:35
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awygleah, yes. that's a known problem with abc eating net names...17:41
awygleone moment, i have something for you to try...17:41
awygleso there's an ABC command called "dress" which supposedly can recover some net names17:43
awyglei'm not entirely sure how to use it but it looks like you need a pre-synthesis netlist for comparison17:45
awygleso i guess you'd give "abc dress" your pre-synthesis and post-par netlists, it would recover names in the post-par list, then you'd run icetime on that?17:45
janrinzejust add 'dress' to abc? (I use abc2)17:46
janrinzeyosys -p 'synth_ice40 -abc2 -top top -blif [email protected]' $<17:48
janrinzeshould become17:48
janrinzeyosys -p 'synth_ice40 -abc2 dress -top top -blif [email protected]' $<17:48
janrinzeis that correct?17:48
janrinzeI was assuming there should be some kind of config for abc that I need to change17:48
awyglei think you might need to call dress from abc directly rather than through yosys, but i'm not sure17:51
janrinzethe documentation is not quite clear on how to add abc flags in yosys17:52
awyglei have not actually tried the dress command so you'd be charting new territory :) you might get better names out of icetime if you pass -noabc instead of -abc2, but you'll get worse results as well, so probably not helpful if you're trying to figure out why you're not meeting timing17:53
janrinzeyes.. abc2 yields best result for my design. switching that off surely will generate a lot worse timings, i agree17:54
janrinzesynth_ice40 seems to be a reference to a script but i cannot find it. it is probably compiled-in in yosys.17:57
tpbTitle: Yosys Open SYnthesis Suite :: Command Reference :: synth_ice40 (at www.clifford.at)17:59
janrinzethat is exactly the page i am looking through.17:59
awygleit's basically just a shortcut for a bunch of other commands17:59
awyglerqou: did you actually try "dress"?18:00
awyglerqou: slash, do you know any other tricks to help janrinze?18:00
janrinzeERROR: Command syntax error: Unexpected option in selection arguments.18:01
janrinzei copied the commands from the documentation and put them into a script for yosys. Unchanged it works okay.18:28
janrinzewhen i add 'dress' to abc , yosys still works but arachne-pnr is not happy anymore..18:29
janrinzefatal error: invalid .names entry: both gates must be 1 here18:29
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