Re: [PATCH V4 1/4] arm_pmu: acpi: Refactor arm_spe_acpi_register_device()

Suzuki K Poulose
2023-08-08T08:48:53Z

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.

> +}
> +
> #if IS_ENABLED(CONFIG_ARM_SPE_PMU)
> static struct resource spe_resources[] = {
> {
> @@ -84,6 +141,11 @@ static struct platform_device spe_dev = {
> .num_resources = ARRAY_SIZE(spe_resources)
> };
>
> +static u16 arm_spe_parse_gsi(struct acpi_madt_generic_interrupt *gicc)
> +{
> + return gicc->spe_interrupt;
> +}
> +
> /*
> * For lack of a better place, hook the normal PMU MADT walk
> * and create a SPE device if we detect a recent MADT with
> @@ -91,47 +153,10 @@ static struct platform_device spe_dev = {
> */
> static void arm_spe_acpi_register_device(void)
> {
> - int cpu, hetid, irq, ret;
> - bool first = true;
> - u16 gsi = 0;
> -
> - /*
> - * Sanity check all the GICC tables for the same interrupt number.
> - * For now, we only support homogeneous ACPI/SPE machines.
> - */
> - for_each_possible_cpu(cpu) {
> - struct acpi_madt_generic_interrupt *gicc;
> -
> - gicc = acpi_cpu_get_madt_gicc(cpu);
> - if (gicc->header.length < ACPI_MADT_GICC_SPE)
> - return;
> -
> - if (first) {
> - gsi = gicc->spe_interrupt;
> - if (!gsi)
> - return;
> - hetid = find_acpi_cpu_topology_hetero_id(cpu);
> - first = false;
> - } else if ((gsi != gicc->spe_interrupt) ||
> - (hetid != find_acpi_cpu_topology_hetero_id(cpu))) {
> - pr_warn("ACPI: SPE must be homogeneous\n");
> - return;
> - }
> - }
> -
> - irq = acpi_register_gsi(NULL, gsi, ACPI_LEVEL_SENSITIVE,
> - ACPI_ACTIVE_HIGH);
> - if (irq < 0) {
> - pr_warn("ACPI: SPE Unable to register interrupt: %d\n", gsi);
> - return;
> - }
> -
> - spe_resources[0].start = irq;
> - ret = platform_device_register(&spe_dev);
> - if (ret < 0) {
> + 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 ? 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.

Suzuki

> - acpi_unregister_gsi(gsi);
> - }
> }
> #else
> static inline void arm_spe_acpi_register_device(void)