| Message ID | 0f8ac07472f4161c71247742acb2303f9cf91396.1692113438.git.geert+renesas@glider.be (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | perf: ARM_SMMU_V3_PMU should depend on ARM_SMMU_V3 | expand |
On 2023-08-15 16:36, Geert Uytterhoeven wrote: > There is no point in monitoring transactions passing through the SMMU > when ARM Ltd. System MMU Version 3 (SMMUv3) Support is disabled. > Hence replace the dependency on ARM64 by a dependency on ARM_SMMU_V3 > (which implies the former). > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > This caught my eye after commit 7c3f204e544dfa37 ("perf/smmuv3: Remove > build dependency on ACPI") in arm64/for-next/core. > > Perhaps my understanding is wrong? Is there anything to monitor when > ARM_SMMU_V3=n? Yes, at least TBU event 1 still counts bypass transactions even when the SMMU is disabled, so PMCGs can be useful as basic traffic monitors in their own right. Plus the original design intent was that PMCGs may also be implemented by other things that interact with the SMMU, like ATS-capable PCIe root complexes, or devices with their own internal TLBs, thus they could potentially count any manner of implementation-defined events that aren't necessarily related to SMMU translation. Thanks, Robin. > drivers/perf/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/perf/Kconfig b/drivers/perf/Kconfig > index 273d67ecf6d2530f..c33324692fbf0141 100644 > --- a/drivers/perf/Kconfig > +++ b/drivers/perf/Kconfig > @@ -92,7 +92,7 @@ config ARM_PMU_ACPI > > config ARM_SMMU_V3_PMU > tristate "ARM SMMUv3 Performance Monitors Extension" > - depends on ARM64 || (COMPILE_TEST && 64BIT) > + depends on ARM_SMMU_V3 || (COMPILE_TEST && 64BIT) > depends on GENERIC_MSI_IRQ > help > Provides support for the ARM SMMUv3 Performance Monitor Counter
Hi Robin, On Wed, Aug 16, 2023 at 1:23 PM Robin Murphy <robin.murphy@arm.com> wrote: > On 2023-08-15 16:36, Geert Uytterhoeven wrote: > > There is no point in monitoring transactions passing through the SMMU > > when ARM Ltd. System MMU Version 3 (SMMUv3) Support is disabled. > > Hence replace the dependency on ARM64 by a dependency on ARM_SMMU_V3 > > (which implies the former). > > > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > > --- > > This caught my eye after commit 7c3f204e544dfa37 ("perf/smmuv3: Remove > > build dependency on ACPI") in arm64/for-next/core. > > > > Perhaps my understanding is wrong? Is there anything to monitor when > > ARM_SMMU_V3=n? > > Yes, at least TBU event 1 still counts bypass transactions even when the > SMMU is disabled, so PMCGs can be useful as basic traffic monitors in > their own right. Plus the original design intent was that PMCGs may also > be implemented by other things that interact with the SMMU, like > ATS-capable PCIe root complexes, or devices with their own internal > TLBs, thus they could potentially count any manner of > implementation-defined events that aren't necessarily related to SMMU > translation. Thanks for the explanation! Hereby I withdraw my patch. Gr{oetje,eeting}s, Geert
diff --git a/drivers/perf/Kconfig b/drivers/perf/Kconfig index 273d67ecf6d2530f..c33324692fbf0141 100644 --- a/drivers/perf/Kconfig +++ b/drivers/perf/Kconfig @@ -92,7 +92,7 @@ config ARM_PMU_ACPI config ARM_SMMU_V3_PMU tristate "ARM SMMUv3 Performance Monitors Extension" - depends on ARM64 || (COMPILE_TEST && 64BIT) + depends on ARM_SMMU_V3 || (COMPILE_TEST && 64BIT) depends on GENERIC_MSI_IRQ help Provides support for the ARM SMMUv3 Performance Monitor Counter
There is no point in monitoring transactions passing through the SMMU when ARM Ltd. System MMU Version 3 (SMMUv3) Support is disabled. Hence replace the dependency on ARM64 by a dependency on ARM_SMMU_V3 (which implies the former). Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> --- This caught my eye after commit 7c3f204e544dfa37 ("perf/smmuv3: Remove build dependency on ACPI") in arm64/for-next/core. Perhaps my understanding is wrong? Is there anything to monitor when ARM_SMMU_V3=n? drivers/perf/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)