From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932175Ab3KVSGu (ORCPT ); Fri, 22 Nov 2013 13:06:50 -0500 Received: from co1ehsobe006.messaging.microsoft.com ([216.32.180.189]:15193 "EHLO co1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932137Ab3KVSGp convert rfc822-to-8bit (ORCPT ); Fri, 22 Nov 2013 13:06:45 -0500 X-Forefront-Antispam-Report: CIP:149.199.60.83;KIP:(null);UIP:(null);IPV:NLI;H:xsj-gw1;RD:unknown-60-83.xilinx.com;EFVD:NLI X-SpamScore: -4 X-BigFish: VPS-4(z579ehzbb2dI98dI9371Ic89bh1432I4015Izz1f42h2148h208ch1ee6h1de0h1fdah2073h2149h2146h1202h1e76h1d1ah1d2ah1fc6hzz1de098h8275bh1de097hz2fh95h839h93fhd24hf0ah119dh1288h12a5h12a9h12bdh137ah13b6h1441h14ddh1504h1537h153bh162dh1631h1758h18e1h1946h19b5h1b0ah224fh1d0ch1d2eh1d3fh1dfeh1dffh1e1dh1fe8h1ff5h209eh2216h906i1155h) Date: Fri, 22 Nov 2013 10:06:34 -0800 From: =?utf-8?B?U8O2cmVu?= Brinkmann To: Daniel Lezcano CC: Rob Herring , Pawel Moll , Mark Rutland , Stephen Warren , Ian Campbell , Russell King , Michal Simek , Thomas Gleixner , , , Subject: Re: [PATCH 4/7] clocksource/cadence_ttc: Adjust interval in clock notifier References: <1383945677-29674-1-git-send-email-soren.brinkmann@xilinx.com> <1383945677-29674-5-git-send-email-soren.brinkmann@xilinx.com> <52825779.2050106@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline In-Reply-To: <52825779.2050106@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-RCIS-Action: ALLOW Message-ID: Content-Transfer-Encoding: 8BIT X-OriginatorOrg: xilinx.com X-FOPE-CONNECTOR: Id%0$Dn%*$RO%0$TLS%0$FQDN%$TlsDn% Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Daniel, On Tue, Nov 12, 2013 at 05:29:45PM +0100, Daniel Lezcano wrote: > On 11/08/2013 10:21 PM, Soren Brinkmann wrote: > >The clockevent has to be reprogrammed if the timer's input > >clock frequency changes and the timer is in periodic mode, in order to > >maintain the correct timer interval. > > > >Signed-off-by: Soren Brinkmann > >--- > > drivers/clocksource/cadence_ttc_timer.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > >diff --git a/drivers/clocksource/cadence_ttc_timer.c b/drivers/clocksource/cadence_ttc_timer.c > >index a92350b55d32..68a336038d8f 100644 > >--- a/drivers/clocksource/cadence_ttc_timer.c > >+++ b/drivers/clocksource/cadence_ttc_timer.c > >@@ -338,6 +338,10 @@ static int ttc_rate_change_clockevent_cb(struct notifier_block *nb, > > /* update cached frequency */ > > ttc->freq = ndata->new_rate; > > > >+ if (ttcce->ce.mode == CLOCK_EVT_MODE_PERIODIC) > >+ ttc_set_interval(ttc, DIV_ROUND_CLOSEST(ttc->freq, > >+ PRESCALE * HZ)); > >+ > > Couldn't be racy ? I guess you're right. What would be the proper way to resolve it? If we look at a little more code things look like this: local_irq_save(flags); clockevents_update_freq(&ttcce->ce, ndata->new_rate / PRESCALE); local_irq_restore(flags); /* update cached frequency */ ttc->freq = ndata->new_rate; if (ttcce->ce.mode == CLOCK_EVT_MODE_PERIODIC) ttc_set_interval(ttc, DIV_ROUND_CLOSEST(ttc->freq, PRESCALE * HZ)); Would it be enough to move the ttc_set_interval() call within the section where local IRQs are disabled? I have the feeling for this timer the local_irq_save() may in general not be the right option since the timer is not CPU local. Should we probably change this do irq_disable(ttcce->ce.irq)? Thanks, Sören