Messages in this thread | | | Date | Wed, 9 Aug 2023 13:54:55 +0100 | Subject | Re: [PATCH V4 1/4] arm_pmu: acpi: Refactor arm_spe_acpi_register_device() | From | Suzuki K Poulose <> |
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On 08/08/2023 14:16, Will Deacon wrote: > On Tue, Aug 08, 2023 at 09:48:16AM +0100, Suzuki K Poulose wrote: >> On 08/08/2023 09:22, Anshuman Khandual wrote: >>> Sanity checking all the GICC tables for same interrupt number, and ensuring >>> a homogeneous ACPI based machine, could be used for other platform devices >>> as well. Hence this refactors arm_spe_acpi_register_device() into a common >>> helper arm_acpi_register_pmu_device(). >>> >>> Cc: Catalin Marinas <catalin.marinas@arm.com> >>> Cc: Will Deacon <will@kernel.org> >>> Cc: Mark Rutland <mark.rutland@arm.com> >>> Cc: linux-arm-kernel@lists.infradead.org >>> Cc: linux-kernel@vger.kernel.org >>> Co-developed-by: Will Deacon <will@kernel.org> >>> Signed-off-by: Will Deacon <will@kernel.org> >>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> >>> --- >>> drivers/perf/arm_pmu_acpi.c | 105 ++++++++++++++++++++++-------------- >>> 1 file changed, 65 insertions(+), 40 deletions(-) >>> >>> diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c >>> index 90815ad762eb..72454bef2a70 100644 >>> --- a/drivers/perf/arm_pmu_acpi.c >>> +++ b/drivers/perf/arm_pmu_acpi.c >>> @@ -69,6 +69,63 @@ static void arm_pmu_acpi_unregister_irq(int cpu) >>> acpi_unregister_gsi(gsi); >>> } >>> +static int __maybe_unused >>> +arm_acpi_register_pmu_device(struct platform_device *pdev, u8 len, >>> + u16 (*parse_gsi)(struct acpi_madt_generic_interrupt *)) >>> +{ >>> + int cpu, this_hetid, hetid, irq, ret; >>> + u16 this_gsi, gsi = 0; >>> + >>> + /* >>> + * Ensure that platform device must have IORESOURCE_IRQ >>> + * resource to hold gsi interrupt. >>> + */ >>> + if (pdev->num_resources != 1) >>> + return -ENXIO; >>> + >>> + if (pdev->resource[0].flags != IORESOURCE_IRQ) >>> + return -ENXIO; >>> + >>> + /* >>> + * Sanity check all the GICC tables for the same interrupt >>> + * number. For now, only support homogeneous ACPI machines. >>> + */ >>> + for_each_possible_cpu(cpu) { >>> + struct acpi_madt_generic_interrupt *gicc; >>> + >>> + gicc = acpi_cpu_get_madt_gicc(cpu); >>> + if (gicc->header.length < len) >>> + return gsi ? -ENXIO : 0; >>> + >>> + this_gsi = parse_gsi(gicc); >>> + if (!this_gsi) >>> + return gsi ? -ENXIO : 0; >>> + >>> + this_hetid = find_acpi_cpu_topology_hetero_id(cpu); >>> + if (!gsi) { >>> + hetid = this_hetid; >>> + gsi = this_gsi; >>> + } else if (hetid != this_hetid || gsi != this_gsi) { >>> + pr_warn("ACPI: %s: must be homogeneous\n", pdev->name); >>> + return -ENXIO; >>> + } >>> + } >>> + >>> + irq = acpi_register_gsi(NULL, gsi, ACPI_LEVEL_SENSITIVE, ACPI_ACTIVE_HIGH); >>> + if (irq < 0) { >>> + pr_warn("ACPI: %s Unable to register interrupt: %d\n", pdev->name, gsi); >>> + return -ENXIO; >>> + } >>> + >>> + pdev->resource[0].start = irq; >>> + ret = platform_device_register(pdev); >>> + if (ret < 0) { >>> + pr_warn("ACPI: %s: Unable to register device\n", pdev->name); >>> + acpi_unregister_gsi(gsi); >>> + } >>> + return ret; >> >> A postivie return value here could confuse the caller. Also, with my comment >> below, we don't really need to return something from here. > > How does this return a positive value?
Right now, there aren't. My point is this function returns a "return value" of another function. And the caller of this function doesn't really follow the "check" it needs. e.g.:
ret = foo(); if (ret < 0) error; return ret;
And the caller only checks for
if (ret) error;
This seems fragile.
> >>> + int ret = arm_acpi_register_pmu_device(&spe_dev, ACPI_MADT_GICC_SPE, >>> + arm_spe_parse_gsi); >>> + if (ret) >>> pr_warn("ACPI: SPE: Unable to register device\n"); >> >> With this change, a system without SPE interrupt description always >> generates the above message. Is this intended ? > > If there are no irqs, why doesn't this return 0?
Apologies, I missed that.
> arm_acpi_register_pmu_device() should only fail if either: > > - The static resources passed in are broken > - The tables are not homogeneous > - We fail to register the interrupt > > so something is amiss.
Agreed. We don't need duplicate messages about an error ? i.e., one in arm_acpi_register_pmu_device() and another one in the caller ? (Of course adding any missing error msgs).
> >> Could we not drop the above message as all the other possible error >> scenarios are reported. We could simply make the above helper void, see my >> comment above. > > I disagree. If the ACPI tables are borked, we should print a message saying > so.
Ok, fair point.
Suzuki
> > Will
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