Re: [PATCH 0/3] arm-smmu-v3: Add PMCG child support and update PMU MMIO mapping

Robin Murphy
2026-04-08T11:15:47Z

On 2026-04-08 8:51 am, Peng Fan (OSS) wrote:
> This patch series adds proper support for describing and probing the
> Arm SMMU v3 PMCG (Performance Monitor Control Group) as a child node of
> the SMMU in Devicetree, and updates the relevant drivers accordingly.
>
> The SMMU v3 architecture allows an optional PMCG block, typically
> associated with TCUs, to be implemented within the SMMU register
> address space. For example, mmu700 PMCG is at the offset 0x2000 of the
> TCU page 0.

But what's wrong with the existing binding? Especially given that it
even has an upstream user already:

https://git.kernel.org/torvalds/c/aef9703dcbf8

> Patch 1 updates the SMMU v3 Devicetree binding to allow PMCG child nodes,
> referencing the existing arm,smmu-v3-pmcg binding.
>
> Patch 2 updates the arm-smmu-v3 driver to populate platform devices for
> child nodes described in DT once the SMMU probe succeeds.
>
> Patch 3 updates the SMMUv3 PMU driver to correctly handle MMIO mapping when
> PMCG is described as a child node. The PMCG registers occupy a sub-region
> of the parent SMMU MMIO window, which is already requested by the SMMU

That has not been the case since 52f3fab0067d ("iommu/arm-smmu-v3: Don't
reserve implementation defined register space") nearly 6 years ago,
where the whole purpose was to support Arm's PMCG implementation
properly. What kernel is this based on?

Thanks,
Robin.

> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
> Peng Fan (3):
> dt-bindings: iommu: arm-smmu-v3: Allow PMU child nodes
> iommu/arm-smmu-v3: Populate PMU child devices from Devicetree
> perf/arm-smmuv3: Avoid double-requesting shared SMMU MMIO for PMCG
>
> .../devicetree/bindings/iommu/arm,smmu-v3.yaml | 10 ++++++++++
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 3 +++
> drivers/perf/arm_smmuv3_pmu.c | 19 ++++++++++++++++---
> 3 files changed, 29 insertions(+), 3 deletions(-)
> ---
> base-commit: f3e6330d7fe42b204af05a2dbc68b379e0ad179e
> change-id: 20260408-smmu-perf-754367fe66c8
>
> Best regards,