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

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Date:   Tue, 13 Nov 2018 14:14:31 +1100 (AEDT)
From:   Finn Thain <fthain@...egraphics.com.au>
To:     Michael Schmitz <schmitzmic@...il.com>
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

On Tue, 13 Nov 2018, Michael Schmitz wrote:

> Hi Finn,
> 
> Am 12.11.2018 um 22:06 schrieb Finn Thain:
> > On Mon, 12 Nov 2018, Geert Uytterhoeven wrote:
> > 
> > > Hi Finn,
> > > 
> > > Thanks for your patch!
> > > 
> > > On Mon, Nov 12, 2018 at 5:46 AM Finn Thain <fthain@...egraphics.com.au>
> > > wrote:
> > > > The functions that implement arch_gettimeoffset are re-used by
> > > > new clocksource drivers in subsequent patches.
> > > 
> > > Disabling this first affects functionality during bisection, right?
> > > 
> > 
> > It means that all platforms have to use the 'jiffies' clocksource.
> 
> So all that happens is timer granularity drops to 10ms, then gets restored by
> the later patches?
> 

Yes, that was the plan, but I can't confirm that it worked out as I don't 
have any physical 68k hardware in front of me right now. If you can 
confirm this on your Atari Falcon, that would be great.

(It appears that a QEMU-emulated Mac does not benefit from having a 
clocksource that's more accurate than the 'jiffies' clocksource, in spite 
of "clocksource: Switched to clocksource via1".)

The latest patches can be found at
https://github.com/fthain/linux/commits/mac68k-queue/

-- 

> I doubt that would be a large enough regression to matter for bisection, but
> the way you reuse the arch_gettimeoffset() code for the new read_clock()
> functions makes reordering of this patch to the end of the series impossible.
> 
> Best you can don, under the circumstances.
> 
> Cheers,
> 
> 	Michael
> 
>