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Date: Wed, 29 Mar 2017 17:32:28 +0200 From: Daniel Lezcano <daniel.lezcano@...aro.org> To: Mark Rutland <mark.rutland@....com> Cc: fu.wei@...aro.org, rjw@...ysocki.net, lenb@...nel.org, tglx@...utronix.de, marc.zyngier@....com, lorenzo.pieralisi@....com, sudeep.holla@....com, hanjun.guo@...aro.org, linux-arm-kernel@...ts.infradead.org, linaro-acpi@...ts.linaro.org, linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org, rruigrok@...eaurora.org, harba@...eaurora.org, cov@...eaurora.org, timur@...eaurora.org, graeme.gregory@...aro.org, al.stone@...aro.org, jcm@...hat.com, wei@...hat.com, arnd@...db.de, catalin.marinas@....com, will.deacon@....com, Suravee.Suthikulpanit@....com, leo.duran@....com, wim@...ana.be, linux@...ck-us.net, linux-watchdog@...r.kernel.org, tn@...ihalf.com, christoffer.dall@...aro.org, julien.grall@....com Subject: Re: [PATCH v22 03/11] clocksource: arm_arch_timer: refactor arch_timer_needs_probing 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@...aro.org wrote: > > > From: Fu Wei <fu.wei@...aro.org> > > > > > > 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. -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
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