From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: [PATCH v22 03/11] clocksource: arm_arch_timer: refactor arch_timer_needs_probing Date: Wed, 29 Mar 2017 17:32:28 +0200 Message-ID: <20170329153228.GN2123@mai> References: <20170321163122.9183-1-fu.wei@linaro.org> <20170321163122.9183-4-fu.wei@linaro.org> <20170328150220.GF2123@mai> <20170329152408.GM23442@leverpostej> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Received: from mail-wr0-f179.google.com ([209.85.128.179]:36006 "EHLO mail-wr0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753930AbdC2Pcf (ORCPT ); Wed, 29 Mar 2017 11:32:35 -0400 Received: by mail-wr0-f179.google.com with SMTP id w11so19704545wrc.3 for ; Wed, 29 Mar 2017 08:32:34 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20170329152408.GM23442@leverpostej> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Mark Rutland Cc: fu.wei@linaro.org, rjw@rjwysocki.net, lenb@kernel.org, tglx@linutronix.de, marc.zyngier@arm.com, lorenzo.pieralisi@arm.com, sudeep.holla@arm.com, hanjun.guo@linaro.org, linux-arm-kernel@lists.infradead.org, linaro-acpi@lists.linaro.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, rruigrok@codeaurora.org, harba@codeaurora.org, cov@codeaurora.org, timur@codeaurora.org, graeme.gregory@linaro.org, al.stone@linaro.org, jcm@redhat.com, wei@redhat.com, arnd@arndb.de, catalin.marinas@arm.com, will.deacon@arm.com, Suravee.Suthikulpanit@amd.com, leo.duran@amd.com, wim@iguana.be, linux@roeck-us.net, linux-watchdog@vger.kernel.org, tn@semihalf.com, christoffer.dall@linaro.org, julien.grall@arm.com On Wed, Mar 29, 2017 at 04:24:08PM +0100, Mark Rutland wrote: > On Tue, Mar 28, 2017 at 05:02:20PM +0200, Daniel Lezcano wrote: > > On Wed, Mar 22, 2017 at 12:31:14AM +0800, fu.wei@linaro.org wrote: > > > From: Fu Wei > > > > > > When system init with device-tree, we don't know which node will be > > > initialized first. And the code in arch_timer_common_init should wait > > > until per-cpu timer and MMIO timer are both initialized. So we need > > > arch_timer_needs_probing to detect the init status of system. > > > > > > But currently the code is dispersed in arch_timer_needs_probing and > > > arch_timer_common_init. And the function name doesn't specify that > > > it's only for device-tree. This is somewhat confusing. > > > > Can the following patch help you to solve nicely the situation ? > > > > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1360007.html > > This does not help. > > The needs_probing logic is all there to bodge around a problem with > registering sched_clock, when you have two sources of the same > frequency, but one is otherwise better. > > The sysreg clocksource has much lower latency than the MMIO clocksource, > so we always want to use that as the sched_clock if we have it. > Currently, the code ensures this by deferring registration of > sched_clock. > > Ideally, we'd figure that out dynamically, or we'd have a rating > argument. > Ok, I see. Thanks. -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog