linux-kernel - Re: [PATCH 1/3] arm_pmu: acpi: Add a representative platform device for TRBE

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Message-ID: <20230728144056.GE21718@willie-the-truck>
Date:   Fri, 28 Jul 2023 15:40:57 +0100
From:   Will Deacon <will@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, suzuki.poulose@....com,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] arm_pmu: acpi: Add a representative platform device
 for TRBE

On Fri, Jul 28, 2023 at 04:57:31PM +0530, Anshuman Khandual wrote:
> ACPI TRBE does not have a HID for identification which could create and add
> a platform device into the platform bus. Also without a platform device, it
> cannot be probed and bound to a platform driver.
> 
> This creates a dummy platform device for TRBE after ascertaining that ACPI
> provides required interrupts uniformly across all cpus on the system. This
> device gets created inside drivers/perf/arm_pmu_acpi.c to accommodate TRBE
> being built as a module.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>

--->8

> diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
> index 90815ad762eb..dd3df6729808 100644
> --- a/drivers/perf/arm_pmu_acpi.c
> +++ b/drivers/perf/arm_pmu_acpi.c
> @@ -139,6 +139,68 @@ static inline void arm_spe_acpi_register_device(void)
>  }
>  #endif /* CONFIG_ARM_SPE_PMU */
>  
> +#ifdef CONFIG_CORESIGHT_TRBE
> +static struct resource trbe_acpi_resources[] = {
> +	{
> +		/* irq */
> +		.flags          = IORESOURCE_IRQ,
> +	}
> +};
> +
> +static struct platform_device trbe_acpi_dev = {
> +	.name = ARMV8_TRBE_PDEV_NAME,
> +	.id = -1,
> +	.resource = trbe_acpi_resources,
> +	.num_resources = ARRAY_SIZE(trbe_acpi_resources)
> +};
> +
> +static void arm_trbe_acpi_register_device(void)
> +{
> +	int cpu, hetid, irq, ret;
> +	bool first = true;
> +	u16 gsi = 0;
> +
> +	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_TRBE)
> +			return;
> +
> +		if (first) {
> +			gsi = gicc->trbe_interrupt;
> +			if (!gsi)
> +				return;
> +
> +			hetid = find_acpi_cpu_topology_hetero_id(cpu);
> +			first = false;
> +		} else if ((gsi != gicc->trbe_interrupt) ||
> +			   (hetid != find_acpi_cpu_topology_hetero_id(cpu))) {
> +			pr_warn("ACPI: TRBE must be homogeneous\n");
> +			return;
> +		}
> +	}
> +
> +	irq = acpi_register_gsi(NULL, gsi, ACPI_LEVEL_SENSITIVE, ACPI_ACTIVE_HIGH);
> +	if (irq < 0) {
> +		pr_warn("ACPI: TRBE Unable to register interrupt: %d\n", gsi);
> +		return;
> +	}
> +	trbe_acpi_resources[0].start = irq;
> +
> +	ret = platform_device_register(&trbe_acpi_dev);
> +	if (ret < 0) {
> +		pr_warn("ACPI: TRBE: Unable to register device\n");
> +		acpi_unregister_gsi(gsi);
> +	}
> +}
> +#else
> +static inline void arm_trbe_acpi_register_device(void)
> +{
> +
> +}
> +#endif /* CONFIG_CORESIGHT_TRBE */

This looks like you ran s/spe/trbe/ over the SPE device registration
code :)

Please can you refactor things so we don't have all the duplication? I
suspect this won't be the last device which needs the same treatement.

Cheers,

Will