From mboxrd@z Thu Jan 1 00:00:00 1970 From: afzal.mohd.ma@gmail.com (Afzal Mohammed) Date: Mon, 5 Oct 2015 17:19:40 +0530 Subject: Dropping "depends on SMP" for HAVE_ARM_TWD -- take 2 In-Reply-To: <20151005054652.GI26391@xsjsorenbubuntu> References: <560E53E3.7070207@free.fr> <560E8584.8000207@free.fr> <20151002180255.GK12338@codeaurora.org> <560ED1FB.9010000@free.fr> <20151003103219.1e10bdeb@arm.com> <560FA4B5.1040709@free.fr> <20151003111231.544ae8e2@arm.com> <20151005054652.GI26391@xsjsorenbubuntu> Message-ID: <20151005114940.GA4448@afzalpc> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, On Sun, Oct 04, 2015 at 10:46:52PM -0700, S?ren Brinkmann wrote: > On Sat, 2015-10-03 at 11:12AM +0100, Marc Zyngier wrote: > > Indeed, I cannot see any code that does that in the GT driver. But if > > you have an A9 MP, you probably want to stick to TWD, which gives you a > > per-cpu timer instead of a global timer that will require IPIs to other > > CPUs. > > I think the TWD only provides a clock_event device. Clocksource and > schedclock would have to be provided by something else. If no clocksource, sched clock is provided, default jiffies based ones would be sufficient for single core, no ?, though not a preferred one. Regards afzal > I looked at that once. IIRC, the problems are schedclock and clocksource. > Other than a clockevent device which can be adjusted for frequency > changes, there is (at least was) no such mechanism for clocksources and > schedclock. Those are required to run at a stable frequency at all times