linux-kernel - Re: [PATCH v22 03/11] clocksource: arm_arch_timer: refactor arch_timer_needs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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