Re: [PATCH v5 08/15] iommu/arm-smmu-v3: Disable the queue IRQs before disabling the SMMU

[Nicolin Chen <nicolinc@nvidia.com>]

On Wed, Sep 23, 2026 at 03:37:05PM -0300, Jason Gunthorpe wrote:
> > The EVTQ, PRIQ and combined IRQ handlers are threaded and issue commands of
> > their own, e.g. a CMDQ_OP_PRI_RESP for a page request. Disabling the SMMU
> > while one is in flight hands that command to a queue consuming nothing, so
> > its poll waits out a full timeout.
> 
> This seems like a sashiko hallucination?
> 
> There are no PRIs during probe. The initial STE table does not permit
> it.

Checked my long rework history. Yes... my bad..

> > Two paths disable the SMMU while those IRQs are still requested: a failing
> > arm_smmu_device_reset() returns to a probe that disables the device itself,
> > and arm_smmu_disable_action() covers an unbind or any later probe failure.
> > Both can run after arm_smmu_setup_irqs() requested the IRQs.
> 
> That's fscking devm again. Do not mix devm and non devm CALLS. It
> doesn't work:
> 
> 	ret = arm_smmu_device_reset(smmu);
> 	if (ret) {
> 		arm_smmu_device_disable(smmu);   <-------------------
> 		return ret;
> 	}
> 
> 	/* Register last so it unwinds first, while the CMDQ is still up. */
> 	ret = devm_add_action_or_reset(smmu->dev, arm_smmu_disable_action, smmu);
> 	if (ret)
> 		return ret;

This seems requiring a reorder.

> When devm is devm'ing properly the existing devm irq handlers will be
> torn down before disable_action and we don't need to open code a
> disable_irq

I see. Yes.

> That just leaves shutdown, and I'm not sure how that is supposed to
> work, we can't just halt the SMMU while there are any threads running
> around still poking at it. I forget the context shutdown runs in, but
> if concurrency is shut down already then its fine to not disable the
> irqs.
> 
> If not, it doesn't work safely for lots of reasons, and disable_irq is
> not going to fix it enough.
> 
> Maybe that is something to tackle after the power management series as
> shutdown is sort of like power down.

OK. Let's leave it.

Thanks
Nicolin