Re: [PATCH v8 15/21] ARM64 / ACPI: Introduce ACPI_IRQ_MODEL_GIC and register device's gsi

[Will Deacon <will.deacon@arm.com>]

On Mon, Feb 02, 2015 at 12:45:43PM +0000, Hanjun Guo wrote:
> Introduce ACPI_IRQ_MODEL_GIC which is needed for ARM64 as GIC is
> used, and then register device's gsi with the core IRQ subsystem.
> 
> acpi_register_gsi() is similar to DT based irq_of_parse_and_map(),
> since gsi is unique in the system, so use hwirq number directly
> for the mapping.
> 
> We are going to implement stacked domains when GICv2m, GICv3, ITS
> support are added.
> 
> CC: Marc Zyngier <marc.zyngier@arm.com>
> Originally-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
> Tested-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
> Tested-by: Yijing Wang <wangyijing@huawei.com>
> Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
> Tested-by: Jon Masters <jcm@redhat.com>
> Tested-by: Timur Tabi <timur@codeaurora.org>
> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
> ---
>  arch/arm64/kernel/acpi.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/acpi/bus.c       |  3 ++
>  include/linux/acpi.h     |  1 +
>  3 files changed, 77 insertions(+)
> 
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index f80caef..f86a982 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -38,6 +38,12 @@ EXPORT_SYMBOL(acpi_pci_disabled);
>  static int enabled_cpus;	/* Processors (GICC) with enabled flag in MADT */
>  
>  /*
> + * Since we're on ARM, the default interrupt routing model
> + * clearly has to be GIC.
> + */
> +enum acpi_irq_model_id acpi_irq_model = ACPI_IRQ_MODEL_GIC;
> +
> +/*
>   * __acpi_map_table() will be called before page_init(), so early_ioremap()
>   * or early_memremap() should be called here to for ACPI table mapping.
>   */
> @@ -185,6 +191,73 @@ void __init acpi_init_cpus(void)
>  	pr_info("%d CPUs enabled, %d CPUs total\n", enabled_cpus, total_cpus);
>  }
>  
> +int acpi_gsi_to_irq(u32 gsi, unsigned int *irq)
> +{
> +	*irq = irq_find_mapping(NULL, gsi);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(acpi_gsi_to_irq);
> +
> +/*
> + * success: return IRQ number (>0)
> + * failure: return =< 0
> + */
> +int acpi_register_gsi(struct device *dev, u32 gsi, int trigger, int polarity)
> +{
> +	unsigned int irq;
> +	unsigned int irq_type;
> +
> +	/*
> +	 * ACPI have no bindings to indicate SPI or PPI, so we
> +	 * use different mappings from DT in ACPI.
> +	 *
> +	 * For FDT
> +	 * PPI interrupt: in the range [0, 15];
> +	 * SPI interrupt: in the range [0, 987];
> +	 *
> +	 * For ACPI, GSI should be unique so using
> +	 * the hwirq directly for the mapping:
> +	 * PPI interrupt: in the range [16, 31];
> +	 * SPI interrupt: in the range [32, 1019];
> +	 */
> +
> +	if (trigger == ACPI_EDGE_SENSITIVE &&
> +				polarity == ACPI_ACTIVE_LOW)
> +		irq_type = IRQ_TYPE_EDGE_FALLING;
> +	else if (trigger == ACPI_EDGE_SENSITIVE &&
> +				polarity == ACPI_ACTIVE_HIGH)
> +		irq_type = IRQ_TYPE_EDGE_RISING;
> +	else if (trigger == ACPI_LEVEL_SENSITIVE &&
> +				polarity == ACPI_ACTIVE_LOW)
> +		irq_type = IRQ_TYPE_LEVEL_LOW;
> +	else if (trigger == ACPI_LEVEL_SENSITIVE &&
> +				polarity == ACPI_ACTIVE_HIGH)
> +		irq_type = IRQ_TYPE_LEVEL_HIGH;
> +	else
> +		irq_type = IRQ_TYPE_NONE;
> +
> +	/*
> +	 * Since only one GIC is supported in ACPI 5.0, we can
> +	 * create mapping refer to the default domain
> +	 */
> +	irq = irq_create_mapping(NULL, gsi);
> +	if (!irq)
> +		return irq;
> +
> +	/* Set irq type if specified and different than the current one */
> +	if (irq_type != IRQ_TYPE_NONE &&
> +		irq_type != irq_get_trigger_type(irq))
> +		irq_set_irq_type(irq, irq_type);
> +	return irq;
> +}
> +EXPORT_SYMBOL_GPL(acpi_register_gsi);
> +
> +void acpi_unregister_gsi(u32 gsi)
> +{
> +}
> +EXPORT_SYMBOL_GPL(acpi_unregister_gsi);
> +
>  static int __init acpi_parse_fadt(struct acpi_table_header *table)
>  {
>  	struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;

Does this code *have* to sit under arch/arm64? I can't see anything
architecture-specific about it and the bulk of the functions map directly
onto irq domain callbacks. I know that the answer is probably "we can fix
that in the future", but it doesn't seem like a huge amount of effort to
get the right abstractions in place from the beginning so that we don't
have to churn this stuff later on.

Will