Re: perf getting all-zeroes IP on STM32MP1

[Florian Bezdeka <florian.bezdeka@siemens.com>]

On Tue, 2026-09-08 at 10:16 +0200, Philippe Gerum wrote:
> 
> > 
> > We could ask the clock_event_device (real device) for it's IRQ and mark
> > it  as __IRQF_TIMER during proxy registration.
> > 
> > The following seems to work, but might need some more work.
> > 
> > The on_each_cpu() part is likely a overkill due to percpu IRQs, but the
> > real_dev part of mark_timer_tick_irq() is local CPU specific as well.
> > 
> > diff --git a/kernel/time/tick-proxy.c b/kernel/time/tick-proxy.c
> > index 6ef04fcf5dacd..55526cd99e849 100644
> > --- a/kernel/time/tick-proxy.c
> > +++ b/kernel/time/tick-proxy.c
> > @@ -296,6 +296,22 @@ static int enable_oob_timer(void *arg) /* hard_irqs_disabled() */
> >  	return 0;
> >  }
> >  
> > +static void mark_timer_tick_irq(void *arg)
> > +{
> > +	struct clock_event_device *real_dev;
> > +	struct irq_desc *desc;
> > +	int irq;
> > +
> > +	real_dev = raw_cpu_ptr(&tick_cpu_device)->evtdev;
> > +	irq = real_dev->irq;
> > +	desc = irq_to_desc(irq);
> > +
> > +	if (!desc || !desc->action)
> > +		return;
> > +
> > +	desc->action->flags |= __IRQF_TIMER;
> > +}
> > +
> >  struct proxy_install_arg {
> >  	void (*setup_proxy)(struct clock_proxy_device *dev);
> >  	int result;
> > @@ -400,6 +416,8 @@ int tick_install_proxy(void (*setup_proxy)(struct clock_proxy_device *dev),
> >  		return arg.result;
> >  	}
> >  
> > +	on_each_cpu(mark_timer_tick_irq, NULL, true);
> > +
> >  	/*
> >  	 * Start ticking from the out-of-band interrupt stage upon
> >  	 * receipt of out-of-band timer events.
> 
> Almost there, but we still need to provide the registers used in
> profiling when no proxy is registered, in which case we cannot depend on
> proxy registration for this, but on clock event device registration
> instead.

diff --git a/kernel/irq/pipeline.c b/kernel/irq/pipeline.c
index 85ec0cbf5fb1e..c4eda1243b915 100644
--- a/kernel/irq/pipeline.c
+++ b/kernel/irq/pipeline.c
@@ -1064,7 +1064,7 @@ void copy_timer_regs(struct irq_desc *desc, struct pt_regs *regs)
 {
 	struct irq_pipeline_data *p;
 
-	if (desc->action == NULL || !(desc->action->flags & __IRQF_TIMER))
+	if (desc->action == NULL || !(desc->action->flags & IRQF_DEFERRED_TIMER))
 		return;
 	/*
 	 * Given our deferred dispatching model for regular IRQs, we
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 90fae659e4ea6..9296164c1d198 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -326,6 +326,16 @@ bool tick_check_replacement(struct clock_event_device *curdev,
 	return tick_check_preferred(curdev, newdev);
 }
 
+static void tick_mark_deferred_timer_irq(struct clock_event_device *dev)
+{
+	struct irq_desc *desc = irq_to_desc(dev->irq);
+
+	if (!desc || !desc->action)
+		return;
+
+	desc->action->flags |= IRQF_DEFERRED_TIMER;
+}
+
 /*
  * Check, if the new registered device should be used. Called with
  * clockevents_lock held and interrupts disabled.
@@ -367,6 +377,8 @@ void tick_check_new_device(struct clock_event_device *newdev)
 	tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
 	if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
 		tick_oneshot_notify();
+	if (newdev->features & CLOCK_EVT_FEAT_PIPELINE)
+		tick_mark_deferred_timer_irq(newdev);
 	return;
 
 out_bc: