On Thu, 14 Aug 2025 11:13:47 +0100,
Steven Price [off-list ref] wrote:

On 07/08/2025 17:02, Marc Zyngier wrote:

quoted

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@kernel.org>
---
 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

[...]

quoted

+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@canb.auug.org.au.

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.