Re: [PATCH v4 2/4] perf: Add Arm Bus Monitor Unit driver

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] perf: arm-bmu: driver omitted when
  ARM_CORESIGHT_PMU_ARCH_SYSTEM_PMU is n or m
--

commit 0be62f2184bd603abec9ec13cdc4790db8588fea
Author: Robin Murphy <robin.murphy@arm.com>

perf: Add Arm Bus Monitor Unit driver

This commit adds a perf driver for Arm's Bus Monitor Unit in
drivers/perf/arm_cspmu/ to support transaction matching and counting across
interface monitoring units.

> diff --git a/drivers/perf/arm_cspmu/Kconfig b/drivers/perf/arm_cspmu/Kconfig
> index 25bd55f036a4f..48c2a3ac7fab5 100644
> --- a/drivers/perf/arm_cspmu/Kconfig
> +++ b/drivers/perf/arm_cspmu/Kconfig
> @@ -34,3 +34,9 @@ config ARM_SYSTEM_PMU
>  	help
>  	  Support additional event filtering attributes for the CoreSight-based
>  	  PMU blocks found in various parts of Arm Compute Subsystems and SoCs.
> +
> +config ARM_BMU
> +	tristate "ARM Bus Monitor Unit"
> +	depends on (ARM64 && ACPI) || COMPILE_TEST
> +	help
> +	  Support perf event counting on Arm Bus Monitor Unit devices.
> diff --git a/drivers/perf/arm_cspmu/Makefile b/drivers/perf/arm_cspmu/Makefile
> index 90c3cd7101577..4e0b420a2b55f 100644
> --- a/drivers/perf/arm_cspmu/Makefile
> +++ b/drivers/perf/arm_cspmu/Makefile
> @@ -9,3 +9,5 @@ arm_cspmu_module-y := arm_cspmu.o
>  obj-$(CONFIG_NVIDIA_CORESIGHT_PMU_ARCH_SYSTEM_PMU) += nvidia_cspmu.o
>  obj-$(CONFIG_AMPERE_CORESIGHT_PMU_ARCH_SYSTEM_PMU) += ampere_cspmu.o
>  obj-$(CONFIG_ARM_SYSTEM_PMU) += arm_syspmu.o
> +
> +obj-$(CONFIG_ARM_BMU) += arm-bmu.o

[Severity: Medium]
Will arm-bmu.o be skipped during the build when
CONFIG_ARM_CORESIGHT_PMU_ARCH_SYSTEM_PMU is disabled or modular?

Unlike the other drivers in this directory, CONFIG_ARM_BMU does not depend on
CONFIG_ARM_CORESIGHT_PMU_ARCH_SYSTEM_PMU, but drivers/perf/Makefile only
descends into arm_cspmu/ via:

drivers/perf/Makefile:
	obj-$(CONFIG_ARM_CORESIGHT_PMU_ARCH_SYSTEM_PMU) += arm_cspmu/

When CONFIG_ARM_CORESIGHT_PMU_ARCH_SYSTEM_PMU=n, Kbuild never enters
drivers/perf/arm_cspmu/ and arm-bmu.o is not built at all; when
CONFIG_ARM_CORESIGHT_PMU_ARCH_SYSTEM_PMU=m and CONFIG_ARM_BMU=y, arm_cspmu/
is only visited for modules and the built-in arm-bmu driver is omitted from
vmlinux.

drivers/perf/Makefile should also add arm_cspmu/ for CONFIG_ARM_BMU (or use
obj-y += arm_cspmu/).

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1793986672.git.robin.murphy@arm.com?part=2