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[122.58.176.92]) by smtp.gmail.com with ESMTPSA id r1-v6sm14040611pfb.69.2018.11.12.20.50.40 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 12 Nov 2018 20:50:45 -0800 (PST) Subject: Re: [RFC PATCH 06/13] m68k: Drop ARCH_USES_GETTIMEOFFSET To: Finn Thain References: <74edaee07800f91eb416ab3e72c4670b8ef4bd4e.1541995959.git.fthain@telegraphics.com.au> Cc: Geert Uytterhoeven , Arnd Bergmann , Stephen N Chivers , Thomas Gleixner , Daniel Lezcano , John Stultz , linux-m68k , Linux Kernel Mailing List , Philip Blundell , Joshua Thompson From: Michael Schmitz Message-ID: Date: Tue, 13 Nov 2018 17:50:37 +1300 User-Agent: Mozilla/5.0 (X11; Linux ppc; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Finn, Am 13.11.2018 um 16:14 schrieb Finn Thain: > 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 >>>> 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. Will do. > (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".) With the current code, kernel log timestamps have 10 ms resolution on Atari. Time resolution of times reported by initcall_debug is roughly 40 us. I'd expect that changes with falling back to jiffies only. Might be worth a try on QEMU Mac. Cheers, Michael > The latest patches can be found at > https://github.com/fthain/linux/commits/mac68k-queue/ >