Re: [PATCH v2 1/4] acpi/irq: implement getter for GSI irqdomain

[Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>]

On Mon, Apr 29, 2019 at 03:12:05PM +0200, Ard Biesheuvel wrote:
> ACPI permits arbitrary producer->consumer interrupt links to be
> described in AML, which means a topology such as the following
> is perfectly legal:
> 
>   Device (EXIU) {
>     Name (_HID, "SCX0008")
>     Name (_UID, Zero)
>     Name (_CRS, ResourceTemplate () {
>       ...
>     })
>   }
> 
>   Device (GPIO) {
>     Name (_HID, "SCX0007")
>     Name (_UID, Zero)
>     Name (_CRS, ResourceTemplate () {
>       Memory32Fixed (ReadWrite, SYNQUACER_GPIO_BASE, SYNQUACER_GPIO_SIZE)
>       Interrupt (ResourceConsumer, Edge, ActiveHigh, ExclusiveAndWake, 0, "\\_SB.EXIU") {
>         7,
>       }
>     })
>     ...
>   }
> 
> The EXIU in this example is the external interrupt unit as can be found
> on Socionext SynQuacer based platforms, which converts a block of 32 SPIs
> from arbitrary polarity/trigger into level-high, with a separate set
> of config/mask/unmask/clear controls.
> 
> The existing DT based driver in drivers/irqchip/irq-sni-exiu.c models
> this as a hierarchical domain stacked on top of the GIC's irqdomain.
> Since the GIC is modeled as a DT node as well, obtaining a reference
> to this irqdomain is easily done by going through the parent link.
> 
> On ACPI systems, however, the GIC is not modeled as an object in the
> namespace, and so device objects cannot refer to it directly. So in
> order to obtain the irqdomain reference when driving the EXIU in ACPI
> mode, we need a helper that returns the default domain for unqualified
> interrupts.
> 
> This is essentially what the ACPI GSI domain provides, so add a helper
> that returns a reference to this domain.

Or we directly export a function in:

drivers/acpi/irq.c

that creates a hierarchical domain with the default GSI domain as a
parent, instead of exporting a function to get that domain from drivers,
this should cut a bit of boilerplate and keep the default GSI domain
handling in ACPI core.

IIUC, the concept is a bit identical to what we did for MBIgen
except that there IORT sets-up the device->msi_domain pointer and
therefore the MBIgen driver does not have to do anything.

Lorenzo

> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
>  drivers/acpi/irq.c   | 14 ++++++++++----
>  include/linux/acpi.h |  1 +
>  2 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/acpi/irq.c b/drivers/acpi/irq.c
> index c3b2222e2129..d47bbd54d4aa 100644
> --- a/drivers/acpi/irq.c
> +++ b/drivers/acpi/irq.c
> @@ -17,6 +17,14 @@ enum acpi_irq_model_id acpi_irq_model;
>  
>  static struct fwnode_handle *acpi_gsi_domain_id;
>  
> +/**
> + * acpi_get_gsi_irqdomain - Retrieve the irqdomain that owns the GSI space.
> + */
> +struct irq_domain *acpi_get_gsi_irqdomain(void)
> +{
> +	return irq_find_matching_fwnode(acpi_gsi_domain_id, DOMAIN_BUS_ANY);
> +}
> +
>  /**
>   * acpi_gsi_to_irq() - Retrieve the linux irq number for a given GSI
>   * @gsi: GSI IRQ number to map
> @@ -29,8 +37,7 @@ static struct fwnode_handle *acpi_gsi_domain_id;
>   */
>  int acpi_gsi_to_irq(u32 gsi, unsigned int *irq)
>  {
> -	struct irq_domain *d = irq_find_matching_fwnode(acpi_gsi_domain_id,
> -							DOMAIN_BUS_ANY);
> +	struct irq_domain *d = acpi_get_gsi_irqdomain();
>  
>  	*irq = irq_find_mapping(d, gsi);
>  	/*
> @@ -76,8 +83,7 @@ EXPORT_SYMBOL_GPL(acpi_register_gsi);
>   */
>  void acpi_unregister_gsi(u32 gsi)
>  {
> -	struct irq_domain *d = irq_find_matching_fwnode(acpi_gsi_domain_id,
> -							DOMAIN_BUS_ANY);
> +	struct irq_domain *d = acpi_get_gsi_irqdomain();
>  	int irq = irq_find_mapping(d, gsi);
>  
>  	irq_dispose_mapping(irq);
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index d5dcebd7aad3..1016027dd626 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -316,6 +316,7 @@ static inline bool acpi_sci_irq_valid(void)
>  extern int sbf_port;
>  extern unsigned long acpi_realmode_flags;
>  
> +struct irq_domain *acpi_get_gsi_irqdomain(void);
>  int acpi_register_gsi (struct device *dev, u32 gsi, int triggering, int polarity);
>  int acpi_gsi_to_irq (u32 gsi, unsigned int *irq);
>  int acpi_isa_irq_to_gsi (unsigned isa_irq, u32 *gsi);
> -- 
> 2.20.1
>