From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: [PATCH 1/2] tick: broadcast: Deny per-cpu clockevents from being broadcast sources Date: Fri, 13 Sep 2013 10:25:57 +0200 Message-ID: <5232CC15.8090208@linaro.org> References: <1379004640-15117-1-git-send-email-soren.brinkmann@xilinx.com> <1379004640-15117-2-git-send-email-soren.brinkmann@xilinx.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Thomas Gleixner Cc: Soren Brinkmann , Rob Herring , Pawel Moll , Mark Rutland , Stephen Warren , Ian Campbell , Russell King , Michal Simek , Stephen Boyd , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: devicetree@vger.kernel.org On 09/12/2013 10:30 PM, Thomas Gleixner wrote: > On Thu, 12 Sep 2013, Soren Brinkmann wrote: >> From: Stephen Boyd >> >> On most ARM systems the per-cpu clockevents are truly per-cpu in >> the sense that they can't be controlled on any other CPU besides >> the CPU that they interrupt. If one of these clockevents were to >> become a broadcast source we will run into a lot of trouble >> because the broadcast source is enabled on the first CPU to go >> into deep idle (if that CPU suffers from FEAT_C3_STOP) and that >> could be a different CPU than what the clockevent is interrupting >> (or even worse the CPU that the clockevent interrupts could be >> offline). >> >> Theoretically it's possible to support per-cpu clockevents as the >> broadcast source but so far we haven't needed this and supporting >> it is rather complicated. Let's just deny the possibility for now >> until this becomes a reality (let's hope it never does!). >=20 > Well, we can't do it this way. There are globally accessible clock > event devices which deliver only to cpu0. So the mask check might be > causing failure here. >=20 > Just add a feature flag CLOCK_EVT_FEAT_PERCPU to the clock event > device and check for it. It sounds probably more understandable than dealing with the cpumasks. I am wondering if this is semantically opposed to http://lwn.net/Articles/566270/ ? [PATCH V3 0/6] cpuidle/ppc: Enable broadcast support for deep idle stat= es -- Daniel --=20 Linaro.org =E2=94=82 Open source software for= ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog * English - detected * English * French * English * French -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html