From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: [PATCH v3 7/8] clocksource/drivers/tegra: Cycles can't be 0 Date: Tue, 18 Jun 2019 17:03:57 +0300 Message-ID: <20190618140358.13148-8-digetx@gmail.com> References: <20190618140358.13148-1-digetx@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190618140358.13148-1-digetx@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Daniel Lezcano , Thierry Reding , Jonathan Hunter , Peter De Schrijver Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-tegra@vger.kernel.org Tegra's timer uses n+1 scheme for the counter, i.e. timer will fire after one tick if 0 is loaded. The minimum and maximum numbers of oneshot ticks are defined by clockevents_config_and_register(min, max) invocation and the min value is set to 1 tick. Hence "cycles" value can't ever be 0, unless it's a bug in clocksource core. Signed-off-by: Dmitry Osipenko --- drivers/clocksource/timer-tegra.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/drivers/clocksource/timer-tegra.c b/drivers/clocksource/timer-tegra.c index 2673b6e0caa8..b84324288749 100644 --- a/drivers/clocksource/timer-tegra.c +++ b/drivers/clocksource/timer-tegra.c @@ -54,9 +54,16 @@ static int tegra_timer_set_next_event(unsigned long cycles, { void __iomem *reg_base = timer_of_base(to_timer_of(evt)); - writel_relaxed(TIMER_PTV_EN | - ((cycles > 1) ? (cycles - 1) : 0), /* n+1 scheme */ - reg_base + TIMER_PTV); + /* + * Tegra's timer uses n+1 scheme for the counter, i.e. timer will + * fire after one tick if 0 is loaded. + * + * The minimum and maximum numbers of oneshot ticks are defined + * by clockevents_config_and_register(1, 0x1fffffff + 1) invocation + * below in the code. Hence the cycles (ticks) can't be outside of + * a range supportable by hardware. + */ + writel_relaxed(TIMER_PTV_EN | (cycles - 1), reg_base + TIMER_PTV); return 0; } -- 2.22.0