linux-kernel - Re: [RFC PATCH 06/13] m68k: Drop ARCH_USES

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Date:   Wed, 14 Nov 2018 14:08:56 +1300
From:   Michael Schmitz <schmitzmic@...il.com>
To:     Finn Thain <fthain@...egraphics.com.au>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        Stephen N Chivers <schivers@....com.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Philip Blundell <philb@....org>,
        Joshua Thompson <funaho@...ai.org>
Subject: Re: [RFC PATCH 06/13] m68k: Drop ARCH_USES_GETTIMEOFFSET

Hi Finn,

On 14/11/18 11:11 AM, Finn Thain wrote:
> On Tue, 13 Nov 2018, Michael Schmitz wrote:
>
>> Running a recent kernel under ARAnyM shows 40 ns resolution so the Atari
>> hardware emulation is a little more complete.
>>
> You mean, 40 us resolution, right?

Sorry, typo. Should have been us of course.

>
>> Using that for initial tests, I can confirm that timer resolution is
>> reduced to 10ms after patch 6, and gets restored to 40ns after applying
>> the full series
> Thanks for testing!
>
>> (once clocksource_init runs, that is - the first part of the boot is at
>> 10ms resolution only, a regression compared to with use of
>> arch_gettimeoffset).
>>
> Sounds like a theoretical regression (?)
>
> Is there any need for more precise timers (I mean, better than 40 us)
> before clocksource_init runs?

I don't think so, given that we can run just fine with 10 ms resolution.

>
>> Unfortunately, I can't log in at the console with all patches applied. I
>> immediately get the 'login timeout exceeded' message. Weird...
>>
> I didn't see that in my tests... Was this aranym or real hardware or both?

ARAnyM only so far.

>
> Can you also test tree fbf8405cd982 please?
>
My tests were on c606b5cf902 in case it wasn't clear. I've now seen 
fbf8405cd982, one moment please ...

That one does appear to work - different versions of ARAnyM, and 
different userland versions though. I'll test that again with the setup 
that saw c606b5cf902 fail.

Cheers,

     Michael