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

[Marc Zyngier <maz@kernel.org>]

On Thu, 23 Jul 2026 10:24:00 +0100,
Jon Hunter <jonathanh@nvidia.com> wrote:
> 
> >>
> >> I have posted something similar for Tegra [0], but because this is not
> >> expected to work, I wanted to avoid the warnings here. We test for
> > 
> > "not expected to work"? In which parallel universe is that a thing?
> 
> FWIU, at least for Tegra194, we have a CPU and GIC pairing where the
> CPU supports this but the GIC does not.

Oh please, you know better than this.

It isn't the GIC that defines the number of supported PPIs, it is the
*integrator*. I.e. you. The GIC (GIC400 in this example) has full
support for 16 PPIs per CPU.

I have a collection of VHE-capable machines with GIC400 that correctly
implement the EL2 virtual timer PPI (if even Amlogic and AllWinner can
get this right, really *anybody* can). My conclusion is that someone
couldn't be bothered to drag a wire from one end to the other.

In any case, the result is the same: a non-working timer, and a
machine that is out of specification.

> 
> >> kernel warnings and ideally we would not warn if is known not to
> >> work. We could always display an info level print if it is needed.
> > 
> > No. These warnings are required because the HW is broken, and violates
> > the basics of the architecture, which the kernel relies on. That's
> > important information that needs to be captured, and that's why the
> > kernel also gets tainted.
> > 
> > This applies to any implementation that hasn't been bothered to follow
> > the spec. Don't worry, you're in good company.
> 
> Well Tegra194 does not appear to have, but Tegra234 does (but we have
> a firmware issue which should be easy to fix but the current released
> firmware as this issue). I have also checked Tegra264 and that should
> be following the spec too.

Then provide a way to unambiguously identify the updated firmware, and
the warning will magically disappear once people update their firmware
to a non-broken version.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.