From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH v3 7/8] clocksource/drivers/tegra: Cycles can't be 0 Date: Tue, 18 Jun 2019 18:51:59 +0100 Message-ID: References: <20190618140358.13148-1-digetx@gmail.com> <20190618140358.13148-8-digetx@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190618140358.13148-8-digetx@gmail.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Dmitry Osipenko , Daniel Lezcano , Thierry Reding , Peter De Schrijver Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-tegra@vger.kernel.org On 18/06/2019 15:03, Dmitry Osipenko wrote: > 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; > } > Acked-by: Jon Hunter Cheers Jon -- nvpublic