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Thu, 30 Apr 2020 18:33:48 +0100 MIME-Version: 1.0 Date: Thu, 30 Apr 2020 18:33:48 +0100 From: Marc Zyngier To: Will Deacon Subject: Re: [PATCH] arm64: perf_event: Fix time_offset for arch timer In-Reply-To: <20200430161815.GE25258@willie-the-truck> References: <20200320093545.28227-1-leo.yan@linaro.org> <20200430145823.GA25258@willie-the-truck> <4d924f705245c797a19d3a73eb0c1ba0@kernel.org> <20200430160436.GC13575@hirez.programming.kicks-ass.net> <20200430161815.GE25258@willie-the-truck> User-Agent: Roundcube Webmail/1.4.3 Message-ID: <79ba3f5f9af951b2de52b8eb9e1bc25f@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: will@kernel.org, peterz@infradead.org, leo.yan@linaro.org, mark.rutland@arm.com, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mathieu.poirier@linaro.org, mike.leach@linaro.org, Al.Grant@arm.com, James.Clark@arm.com, tglx@linutronix.de X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200430_103350_968051_03C17DCE X-CRM114-Status: GOOD ( 12.00 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Al Grant , Mathieu Poirier , Peter Zijlstra , Catalin Marinas , linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Alexander Shishkin , Ingo Molnar , James Clark , Leo Yan , Namhyung Kim , tglx@linutronix.de, Jiri Olsa , linux-arm-kernel@lists.infradead.org, Mike Leach Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-04-30 17:18, Will Deacon wrote: > On Thu, Apr 30, 2020 at 06:04:36PM +0200, Peter Zijlstra wrote: >> On Thu, Apr 30, 2020 at 04:29:23PM +0100, Marc Zyngier wrote: >> >> > I wonder if we could/should make __sched_clock_offset available even when >> > CONFIG_HAVE_UNSTABLE_SCHED_CLOCK isn't defined. It feels like it would >> > help with this particular can or worm... >> >> Errrgh. __sched_clock_offset is only needed on x86 because we >> transition >> from one clock device to another on boot. It really shouldn't exist on >> anything sane. > > I think we still transition from jiffies on arm64, because we don't > register > with sched_clock until the timer driver probes. Marc, is that right? Indeed. The clocksource is only available relatively late, as we need to discover the details of the platform and enable the various workarounds (because nobody can get a simple 64bit counter right). So it is only at that stage that we transition to it. M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel