[Libre-soc-dev] daily kan-ban update 27aug2020

Luke Kenneth Casson Leighton lkcl at lkcl.net
Thu Aug 27 18:50:33 BST 2020

On Thu, Aug 27, 2020 at 6:35 PM Cole Poirier <colepoirier at gmail.com> wrote:
> How are you going about this?

* compiling microwatt core_tb ("make core_tb")
* copying tests/1.bin to main_ram.bin (as shown in scripts/make_test.sh)
* outputting the log to a file
* running litex/florent/sim.py --debug > /tmp/ls.txt
* running litex/florent/sim.py --debug --cpu=microwatt > /tmp/mw.txt
* doing a diff on ls.txt and mw.txt
* when discrepancies are found do a ridiculously laborious process of
analysing the *microwatt* core_tb log file to find the XER and CR
modifications that you *can't* get out via the DMI interface in sim.py
because microwatt doesn't _have_ a way through core_debug.vhdl to
_read_ XER or CR.


> Can I help, perhaps trying to find bugs
> in another part of the HDL? Would need some brief instruction if this
> is the case, but could be a benefit to have a second person working on
> it with you?

the problem is that because of a cascade effect where one error
creates knock-on errors when that register's incorrect value is used
in another instruction, i can only realistically find (then fix) one
instruction at a time.

of course, if you were to use microwatt/tests/2.bin *instead* then yes
you could help because the chances are high that, by running a
different instruction, you'd find a different bug.

it's excruciatingly tedious.

i have to stop typing.  RSI.


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