From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751894AbcAANbQ (ORCPT ); Fri, 1 Jan 2016 08:31:16 -0500 Received: from smtp51.i.mail.ru ([94.100.177.111]:52395 "EHLO smtp51.i.mail.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751836AbcAANah (ORCPT ); Fri, 1 Jan 2016 08:30:37 -0500 From: Roman Volkov To: arm@kernel.org, linux+armsoc@arm.linux.org.uk Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Arnd Bergmann , Alexey Charkov , Roman Volkov , Tony Prisk , Daniel Lezcano , Thomas Gleixner Subject: [PATCH v3 1/3] clocksource/vt8500: Increase the minimum delta Date: Fri, 1 Jan 2016 16:24:41 +0300 Message-Id: <1451654683-2401-2-git-send-email-v1ron@mail.ru> X-Mailer: git-send-email 2.6.4 In-Reply-To: <1451654683-2401-1-git-send-email-v1ron@mail.ru> References: <1451654683-2401-1-git-send-email-v1ron@mail.ru> X-Mras: Ok Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Roman Volkov The vt8500 clocksource driver declares itself as capable to handle the minimum delay of 4 cycles by passing the value into clockevents_config_and_register(). The vt8500_timer_set_next_event() requires the passed cycles value to be at least 16. The impact is that userspace hangs in nanosleep() calls with small delay intervals. This problem is reproducible in Linux 4.2 starting from: c6eb3f70d448 ('hrtimer: Get rid of hrtimer softirq') Signed-off-by: Roman Volkov Acked-by: Alexey Charkov --- drivers/clocksource/vt8500_timer.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/clocksource/vt8500_timer.c b/drivers/clocksource/vt8500_timer.c index a92e94b..dfc3bb4 100644 --- a/drivers/clocksource/vt8500_timer.c +++ b/drivers/clocksource/vt8500_timer.c @@ -50,6 +50,8 @@ #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t) +#define MIN_OSCR_DELTA 16 + static void __iomem *regbase; static cycle_t vt8500_timer_read(struct clocksource *cs) @@ -80,7 +82,7 @@ static int vt8500_timer_set_next_event(unsigned long cycles, cpu_relax(); writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL); - if ((signed)(alarm - clocksource.read(&clocksource)) <= 16) + if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA) return -ETIME; writel(1, regbase + TIMER_IER_VAL); @@ -151,7 +153,7 @@ static void __init vt8500_timer_init(struct device_node *np) pr_err("%s: setup_irq failed for %s\n", __func__, clockevent.name); clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ, - 4, 0xf0000000); + MIN_OSCR_DELTA * 2, 0xf0000000); } CLOCKSOURCE_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init); -- 2.6.2