[PATCH v2] iommu/tegra241-cmdqv: do not use smp_processor_id in preemptible context

[Nicolin Chen]

On Fri, Dec 06, 2024 at 10:01:14AM -0300, Luis Claudio R. Goncalves wrote:
> During boot some of the calls to tegra241_cmdqv_get_cmdq() will happen
> in preemptible context. As this function calls smp_processor_id(), if
> CONFIG_DEBUG_PREEMPT is enabled, these calls will trigger a series of
> "BUG: using smp_processor_id() in preemptible" backtraces.

Confirmed the BUG prints. Should we CC stable tree?

> As tegra241_cmdqv_get_cmdq() only calls smp_processor_id() to use the
> CPU number as a factor to balance out traffic on cmdq usage, it is safe
> to use raw_smp_processor_id() here.
> 
> v2: Sebastian helped identify that the problem was not exclusive to kernels
>     with PREEMPT_RT enabled. The delta between v1 and v2 is the description.
> 
> Signed-off-by: Luis Claudio R. Goncalves <lgoncalv at redhat.com>

Reviewed-by: Nicolin Chen <nicolinc at nvidia.com>
Tested-by: Nicolin Chen <nicolinc at nvidia.com>

Thanks
Nicolin