Re: [PATCH] clocksource/drivers/arm_arch_timer: Workaround bcm2712 broken EL2 virtual timer

[Marc Zyngier]

On Mon, 13 Jul 2026 17:15:35 +0100,
Florian Fainelli <florian.fainelli@xxxxxxxxxxxx> wrote:
> 
> On 7/10/26 01:09, Marc Zyngier wrote:
> > It appears that the bcm2712 SoC found in the relatively popular
> > RPi5 has a broken EL2 virtual timer.
> > 
> > We do not know the reason why the timer isn't working (the timer
> > is ticking, but the interrupt never fires), and the SoC vendor
> > doesn't communicate on the reason why this isn't working, leaving
> > users and maintainers in the dark.
> > 
> > Paper over the issue by detecting the broken HW, falling back to
> > the physical timer instead, and let the user know about it.
> > Also taint the kernel as the machine is definitely not compliant
> > with the spec, and we don't know what else is wrong with it.
> > 
> > Reported-by: John <therealgraysky@xxxxxxxxx>
> > Reported-by: Daniel Drake <dan@xxxxxxxxxxxxxxx>
> > Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> > Cc: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
> > Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> 
> Acked-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
> 
> We know why now: the virtual interrupt timer line was never connected
> in the first place because it was not clarified that it was a
> requirement.

Dangling wires coming out of the CPUs don't ring any alarm bell at
integration time? Amazing. Makes you wonder what else they forgot to
connect...

Is there an erratum number that we can refer to for documentation
purposes?

	M.

-- 
Jazz isn't dead. It just smells funny.