[libre-riscv-dev] [Bug 325] create POWER9 TRAP pipeline

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=325

--- Comment #19 from Cole Poirier <colepoirier at gmail.com> ---
(In reply to Luke Kenneth Casson Leighton from comment #17)
> Cole: example (A is to B, as C is to D).  examine case OP_TRAP and case
> OP_SC.
> 
> A:
>                 ctrl_tmp.irq_nia <= std_logic_vector(to_unsigned(16#C00#,
> 64));
>                 ctrl_tmp.srr1 <= msr_copy(ctrl.msr);
> 
> B:
> 
>                 ????
> 
> 
> C:
>                     ctrl_tmp.irq_nia <=
> std_logic_vector(to_unsigned(16#700#, 64));
>                     ctrl_tmp.srr1 <= msr_copy(ctrl.msr);
> 
> D:
> 
>                     comb += self.o.nia.data.eq(0x700)         # trap address
>                     comb += self.o.nia.ok.eq(1)
> 
> 
> it should be BLINDINGLY obvious that B should be:
> 
>                     comb += self.o.nia.data.eq(0xC00)         # trap address
>                     comb += self.o.nia.ok.eq(1)
> 
> 
> therefore, in switch statement OP_SC, that's what goes into that function.
> 
> and that's it.
> 
> ta-daaa.  OP_SC is completed.
> 
> wasn't that easy?
> 
> Q: do you understand or know what OP_SC is or does?
> A: i don't... and don't care, and it is completely irrelevant to you, as
> well.
> 
>    (it's *optional* to have understanding: you may *desire* understanding,
>     you may *like* to have understanding, but it is, fundamentally,
> *completely
>     irrelevant* to the actual task)
> 
> Q: do we *need* to understand or know what OP_SC is or does?
> A: no we do not.
> 
> Q: will it work?
> A: yes it will.
> 
> Q: will there be bugs?
> A: most probably, and those can be found with unit tests.
> 
> Q: do absolutely all the required unit tests have to be written *right now*?
> A: no they do not.
> 
> Q: do we need to freeze and lock up solid in total fear at our total and
>    complete lack of understanding just because those unit tests do not exist?
> A: of course not.
> 
> so reading a 1300 page PDF is completely and utterly pointless.  and making
> reading that 1300 page PDF a hard, fixed, absolute critical dependency on
> *completing this task* is a false assumption, isn't it?

Very, very helpful. Indeed my false assumption was thankfully very false :)

-- 
You are receiving this mail because:
You are on the CC list for the bug.