Re: [PATCH v2 7/7] irqchip/gic-v5: Add ACPI IWB probing

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Thu, 18 Dec 2025 11:14:33 +0100
Lorenzo Pieralisi <lpieralisi@kernel.org> wrote:

> To probe an IWB in an ACPI based system it is required:
> 
> - to implement the IORT functions handling the IWB IORT node and create
>   functions to retrieve IWB firmware information
> - to augment the driver to match the DSDT ACPI "ARMH0003" device and
>   retrieve the IWB wire and trigger mask from the GSI interrupt descriptor
>   in the IWB msi_domain_ops.msi_translate() function
> 
> Make the required driver changes to enable IWB probing in ACPI systems.
> 
> The GICv5 GSI format requires special handling for IWB routed IRQs.
> 
> Add IWB GSI detection to the top level driver gic_v5_get_gsi_domain_id()
> function so that the correct IRQ domain for a GSI can be detected by
> parsing the GSI and check whether it is an IWB-backed IRQ or not.
> 
> Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Hanjun Guo <guohanjun@huawei.com>
> Cc: Sudeep Holla <sudeep.holla@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
A couple of trivial comments inline. Overall this series looks in a good
state to me.
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
>  drivers/acpi/arm64/iort.c          | 95 ++++++++++++++++++++++++++++++++------
>  drivers/irqchip/irq-gic-v5-iwb.c   | 42 +++++++++++++----
>  drivers/irqchip/irq-gic-v5.c       |  4 ++
>  include/linux/acpi_iort.h          |  1 +
>  include/linux/irqchip/arm-gic-v5.h |  6 +++
>  5 files changed, 123 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index 17dbe66da804..4b0b753db738 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c

> @@ -317,12 +325,28 @@ static acpi_status iort_match_node_callback(struct acpi_iort_node *node,
>  	return status;
>  }
>  
> +static acpi_status iort_match_iwb_callback(struct acpi_iort_node *node, void *context)
> +{
> +	acpi_status status = AE_NOT_FOUND;
> +	u32 *id = context;
> +
> +	if (node->type == ACPI_IORT_NODE_IWB) {
> +		struct acpi_iort_iwb *iwb;
> +
> +		iwb = (struct acpi_iort_iwb *)node->node_data;
> +		status = iwb->iwb_index == *id ? AE_OK : AE_NOT_FOUND;
> +	}
> +
> +	return status;
Simpler flow with a quick exclusion of wrong nodes.
	if (node->type != ACPI_IORT_NODE_IWB)
		return AE_NOT_FOUND;
	....
	iwb = ...
	
Also not sure I'd use a ternary here given it's only slightly more code
as more readable.
	if (iwb->iwb_index != *id)
		return AE_NOT_FOUND;

	return AE_OK;

> +}


> diff --git a/drivers/irqchip/irq-gic-v5-iwb.c b/drivers/irqchip/irq-gic-v5-iwb.c
> index ad9fdc14d1c6..c7d5fd34d053 100644
> --- a/drivers/irqchip/irq-gic-v5-iwb.c
> +++ b/drivers/irqchip/irq-gic-v5-iwb.c
> @@ -4,6 +4,7 @@
>   */
>  #define pr_fmt(fmt)	"GICv5 IWB: " fmt
>  
> +#include <linux/acpi.h>
>  #include <linux/init.h>
>  #include <linux/kernel.h>
>  #include <linux/msi.h>
> @@ -136,18 +137,31 @@ static int gicv5_iwb_irq_domain_translate(struct irq_domain *d, struct irq_fwspe
>  					  irq_hw_number_t *hwirq,
>  					  unsigned int *type)
>  {
> -	if (!is_of_node(fwspec->fwnode))
> -		return -EINVAL;
> +	if (is_of_node(fwspec->fwnode)) {
>  
> -	if (fwspec->param_count < 2)
> -		return -EINVAL;
> +		if (fwspec->param_count < 2)
> +			return -EINVAL;
>  
> -	/*
> -	 * param[0] is be the wire
> -	 * param[1] is the interrupt type
> -	 */
> -	*hwirq = fwspec->param[0];
> -	*type = fwspec->param[1] & IRQ_TYPE_SENSE_MASK;
> +		/*
> +		 * param[0] is be the wire
> +		 * param[1] is the interrupt type
> +		 */
> +		*hwirq = fwspec->param[0];
> +		*type = fwspec->param[1] & IRQ_TYPE_SENSE_MASK;

As below, FIELD_GET() would improve reviewability a little.


> +	}
> +
> +	if (is_acpi_device_node(fwspec->fwnode)) {
> +
> +		if (fwspec->param_count < 2)
> +			return -EINVAL;
> +
> +		/*
> +		 * Extract the wire from param[0]
> +		 * param[1] is the interrupt type
> +		 */
> +		*hwirq = FIELD_GET(GICV5_GSI_IWB_WIRE, fwspec->param[0]);
> +		*type = fwspec->param[1] & IRQ_TYPE_SENSE_MASK;

I'd prefer this FIELD_GET() for this as well so there is no need to
go sanity check that it is the lowest bits.

> +	}
>  
>  	return 0;