Re: [PATCH 0/2] clocksource/drivers/arm_arch_timer_mmio: Restore support for early init

[Marc Zyngier <maz@kernel.org>]

On Wed, 10 Jun 2026 18:53:09 +0100,
Stephan Gerhold <stephan.gerhold@linaro.org> wrote:
> 
> Jack reported a regression for some single-core Qualcomm platforms (e.g.
> MDM9625, MDM9607) that no longer boot because no timers can be found during
> early boot [1].

Again, this is *not* a regression. These machines were *never*
supported upstream.

> These platforms rely on an obscure timer setup where the
> global Arm MMIO timer (arm,armv7-timer-mem) is used as the only available
> timer for the CPU. This setup used to work fine until commit 0f67b56d84b4
> ("clocksource/drivers/arm_arch_timer_mmio: Switch over to standalone
> driver") when the early timer initialization using TIMER_OF_DECLARE() was
> removed when moving to the standalone MMIO driver.
> 
> There doesn't seem to be any other usable CPU timer on those platforms, so
> this series restores the early timer support using TIMER_OF_DECLARE()
> inside the new standalone arm_arch_timer_mmio driver. This is pretty ugly,
> but I could not think of a better solution so far. I tried to keep the
> ugliness for the two probe paths as limited as possible. :-)
> 
> If someone has a better idea how to solve this, I would be happy to try it.

I would suggest finding out what is the latest point in the init
sequence where the timer can be probed without preventing boot.

	M.

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