From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH v3 8/8] clocksource/drivers/tegra: Set up maximum-ticks limit properly Date: Tue, 18 Jun 2019 18:52:33 +0100 Message-ID: References: <20190618140358.13148-1-digetx@gmail.com> <20190618140358.13148-9-digetx@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190618140358.13148-9-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 has 29 bits for the counter and for the "load" register > which sets counter to a load-value. The counter's value is lower than > the actual value by 1 because it starts to decrement after one tick, > hence the maximum number of ticks that hardware can handle equals to > 29 bits + 1. > > Signed-off-by: Dmitry Osipenko > --- > drivers/clocksource/timer-tegra.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/clocksource/timer-tegra.c b/drivers/clocksource/timer-tegra.c > index b84324288749..355b29ff6362 100644 > --- a/drivers/clocksource/timer-tegra.c > +++ b/drivers/clocksource/timer-tegra.c > @@ -137,9 +137,17 @@ static int tegra_timer_setup(unsigned int cpu) > irq_force_affinity(to->clkevt.irq, cpumask_of(cpu)); > enable_irq(to->clkevt.irq); > > + /* > + * Tegra's timer uses n+1 scheme for the counter, i.e. timer will > + * fire after one tick if 0 is loaded and thus minimum number of > + * ticks is 1. In result both of the clocksource's tick limits are > + * higher than a minimum and maximum that hardware register can > + * take by 1, this is then taken into account by set_next_event > + * callback. > + */ > clockevents_config_and_register(&to->clkevt, timer_of_rate(to), > 1, /* min */ > - 0x1fffffff); /* 29 bits */ > + 0x1fffffff + 1); /* max 29 bits + 1 */ > > return 0; > } > Acked-by: Jon Hunter Cheers Jon -- nvpublic