On Thu, 14 Aug 2025 11:13:47 +0100,
Steven Price <steven.price@xxxxxxx> wrote:
>
> On 07/08/2025 17:02, Marc Zyngier wrote:
> > Add a new driver for the MMIO side of the ARM architected timer.
> > Most of it has been lifted from the existing arch timer code,
> > massaged, and finally rewritten.
> >
> > It supports both DT and ACPI as firmware descriptions.
> >
> > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> > ---
> > MAINTAINERS | 1 +
> > drivers/clocksource/arm_arch_timer_mmio.c | 420 ++++++++++++++++++++++
> > 2 files changed, 421 insertions(+)
> > create mode 100644 drivers/clocksource/arm_arch_timer_mmio.c
> >
> [...]
> > +static void arch_timer_mmio_setup(struct arch_timer *at, int irq)
> > +{
> > + at->evt = (struct clock_event_device) {
> > + .features = (CLOCK_EVT_FEAT_ONESHOT |
> > + CLOCK_EVT_FEAT_DYNIRQ),
> > + .name = "arch_mem_timer",
> > + .rating = 400,
> > + .cpumask = cpu_possible_mask,
> > + .irq = irq,
> > + .set_next_event = arch_timer_mmio_set_next_event,
> > + .set_state_oneshot_stopped = arch_timer_mmio_shutdown,
> > + .set_state_shutdown = arch_timer_mmio_shutdown,
> > + };
> > +
> > + at->evt.set_state_shutdown(&at->evt);
> > +
> > + clockevents_config_and_register(&at->evt, at->rate, 0xf, CLOCKSOURCE_MASK(56));
>
> This doesn't work on 32 bit - clockevents_config_and_register()'s final
> argument is an unsigned long, and a 56 bit mask doesn't fit. This
> triggers a compiler warning:
Already reported, see 20250814111657.7debc9f1@xxxxxxxxxxxxxxxx.
> Possible this should really be min(CLOCKSOURCE_MASK(56), ULONG_MAX)? But
> I'm not familiar enough with this code. Most likely it's dead code on a
> 32 bit platform.
No, this definitely exists on 32bit crap, since it has been part of
the architecture from the ARMv7+VE days.
I think this is more of an impedance mismatch between the
CLOCKSOURCE_MASK() helper and the clockevents_config_and_register(),
and a (unsigned long) cast would do the trick.
But it also means that the per-cpu timer also gets truncated the same
way, and that has interesting impacts on how often the timer is
reprogrammed.
Daniel, do you want a patch on top or a new series?
M.
--
Without deviation from the norm, progress is not possible.
