| Message ID | 20190618140358.13148-9-digetx@gmail.com |
|---|---|
| State | Deferred |
| Headers | show |
| Series | Few more cleanups for tegra-timer | expand |
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 <digetx@gmail.com> > --- > 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 <jonathanh@nvidia.com> Cheers Jon
On Tue, Jun 18, 2019 at 05:03:58PM +0300, 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 <digetx@gmail.com> > --- > drivers/clocksource/timer-tegra.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) Acked-by: Thierry Reding <treding@nvidia.com>
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; }
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 <digetx@gmail.com> --- drivers/clocksource/timer-tegra.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)