From mboxrd@z Thu Jan 1 00:00:00 1970 From: Soren Brinkmann Subject: [PATCH v2 3/4] tick: broadcast: Deny per-cpu clockevents from being broadcast sources Date: Wed, 18 Sep 2013 11:48:37 -0700 Message-ID: <1379530118-22813-4-git-send-email-soren.brinkmann@xilinx.com> References: <1379530118-22813-1-git-send-email-soren.brinkmann@xilinx.com> Return-path: In-Reply-To: <1379530118-22813-1-git-send-email-soren.brinkmann@xilinx.com> Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring , Pawel Moll , Mark Rutland , Stephen Warren , Ian Campbell , Russell King , Michal Simek , Thomas Gleixner , Daniel Lezcano , Stephen Boyd , Grant Likely , Preeti Murthy Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Soren Brinkmann List-Id: devicetree@vger.kernel.org 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!). Signed-off-by: Soren Brinkmann --- kernel/time/tick-broadcast.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 218bcb5..9532690 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -70,6 +70,7 @@ static bool tick_check_broadcast_device(struct clock_event_device *curdev, struct clock_event_device *newdev) { if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) || + (newdev->features & CLOCK_EVT_FEAT_PERCPU) || (newdev->features & CLOCK_EVT_FEAT_C3STOP)) return false; -- 1.8.4