Re: [PATCH v2 5/7] irqchip/gic-v5: Add ACPI IRS probing

Jonathan Cameron
2026-01-05T13:24:27Z

On Thu, 18 Dec 2025 11:14:31 +0100
Lorenzo Pieralisi <lpieralisi@kernel.org> wrote:

> On ARM64 ACPI systems GICv5 IRSes are described in MADT sub-entries.
>
> Add the required plumbing to parse MADT IRS firmware table entries and
> probe the IRS components in ACPI.
>
> Refactor the OF based probe so that common code paths can be reused for
> ACPI as well in the process.
>
> Augment the irqdomain_ops.translate() for PPI and SPI IRQs in order to
> provide support for their ACPI based firmware translation.
>
> Implement an irqchip ACPI based callback to initialize the global GSI
> domain upon an MADT IRS detection.
>
> The IRQCHIP_ACPI_DECLARE() entry in the top level GICv5 driver is only used
> to trigger the IRS probing (ie the global GSI domain is initialized once on
> the first call on multi-IRS systems); IRS probing takes place by calling
> acpi_table_parse_madt() in the IRS sub-driver, that probes all IRSes
> in sequence.
>
> Add a new ACPI interrupt model so that it can be detected at runtime and
> distinguished from previous GIC architecture models.
>
> Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
Just a few minor comments inline.

> diff --git a/drivers/irqchip/irq-gic-v5-irs.c b/drivers/irqchip/irq-gic-v5-irs.c
> index ce2732d649a3..07c3df5692af 100644
> --- a/drivers/irqchip/irq-gic-v5-irs.c
> +++ b/drivers/irqchip/irq-gic-v5-irs.c
> @@ -5,6 +5,7 @@
>
> #define pr_fmt(fmt) "GICv5 IRS: " fmt
>
> +#include <linux/acpi.h>
> #include <linux/kmemleak.h>
> #include <linux/log2.h>
> #include <linux/of.h>
> @@ -545,15 +546,15 @@ int gicv5_irs_register_cpu(int cpuid)
>
> static void __init gicv5_irs_init_bases(struct gicv5_irs_chip_data *irs_data,
> void __iomem *irs_base,
> - struct fwnode_handle *handle)
> + struct fwnode_handle *handle,
> + bool noncoherent)
> {
> - struct device_node *np = to_of_node(handle);
> u32 cr0, cr1;
>
> irs_data->fwnode = handle;

Looking this again as you are touching it.

This feels a tiny bit out of place, as not obvious to me why the fwnode being
set is related to initializing bases. Perhaps that belongs at the caller?

> irs_data->irs_base = irs_base;
>
> - if (of_property_read_bool(np, "dma-noncoherent")) {
> + if (noncoherent) {
> /*
> * A non-coherent IRS implies that some cache levels cannot be
> * used coherently by the cores and GIC. Our only option is to mark
> @@ -678,49 +679,13 @@ static void irs_setup_pri_bits(u32 idr1)
> }
> }
>

...

> +static int __init gicv5_irs_of_init(struct device_node *node)
> +{

Not sure whether it would be worth it by inclination would have been
a noop refactor patch, then the ACPI support. I'd have found it a little
bit easier to review.

> + struct gicv5_irs_chip_data *irs_data;
> + void __iomem *irs_base;
> + u8 iaffid_bits;
> + u32 idr;
> + int ret;
> +
> + irs_data = kzalloc(sizeof(*irs_data), GFP_KERNEL);
> + if (!irs_data)
> + return -ENOMEM;
> +
> + raw_spin_lock_init(&irs_data->spi_config_lock);
> +
> + ret = of_property_match_string(node, "reg-names", "ns-config");
> + if (ret < 0) {
> + pr_err("%pOF: ns-config reg-name not present\n", node);
> + goto out_err;

Obviously comes form original code, but this label could give some indication
of where we are going and why. out_free_data maybe?

Perhaps I'm just being fussy as I had to open the code up to check given
it didn't end up in the context.

> + }
> +
...

> +static int __init gic_acpi_parse_iaffid(union acpi_subtable_headers *header,
> + const unsigned long end)
> +{
> + struct acpi_madt_generic_interrupt *gicc = (struct acpi_madt_generic_interrupt *)header;
> + int cpu;
> +
> + if (!(gicc->flags & (ACPI_MADT_ENABLED | ACPI_MADT_GICC_ONLINE_CAPABLE)))
> + return 0;
> +
> + if (gicc->irs_id == current_irsid) {
Unless this is going to get more complex I'd flip the log for an early return on
'not this one'
if (gicc->irs_id != current_irsid)
return 0;

mostly to save on long lines where they aren't needed.

> + cpu = get_logical_index(gicc->arm_mpidr);
> +
> + if (gicc->iaffid & ~GENMASK(current_iaffid_bits - 1, 0)) {
> + pr_warn("CPU %d iaffid 0x%x exceeds IRS iaffid bits\n", cpu, gicc->iaffid);
> + return 0;
> + }
> +
> + // Bind the IAFFID and the CPU
> + per_cpu(cpu_iaffid, cpu).iaffid = gicc->iaffid;
> + per_cpu(cpu_iaffid, cpu).valid = true;
> + pr_debug("Processed IAFFID %u for CPU%d", per_cpu(cpu_iaffid, cpu).iaffid, cpu);
> +
> + // We also know that the CPU is connected to this IRS
> + per_cpu(per_cpu_irs_data, cpu) = current_irs_data;
> + }
> +
> + return 0;
> +}
> +
> +static int __init gicv5_irs_acpi_init_affinity(u32 irsid, struct gicv5_irs_chip_data *irs_data)
> +{
> + u32 idr;
> +
> + current_irsid = irsid;
> + current_irs_data = irs_data;
> +
> + idr = irs_readl_relaxed(irs_data, GICV5_IRS_IDR1);
> + current_iaffid_bits = FIELD_GET(GICV5_IRS_IDR1_IAFFID_BITS, idr) + 1;
> +
> + acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT, gic_acpi_parse_iaffid, 0);
> +
> + return 0;
> +}

> +
> +static int __init gic_acpi_parse_madt_irs(union acpi_subtable_headers *header,
> + const unsigned long end)
> +{
> + struct acpi_madt_gicv5_irs *irs = (struct acpi_madt_gicv5_irs *)header;
> + struct gicv5_irs_chip_data *irs_data;
> + void __iomem *irs_base;
> + struct resource *r;
> + int ret;
> +
> + // Per-IRS data structure

It's your code to look after, so I don't care that strongly but this does
seem to be inconsistent wrt to local style and use of C style
single line comments. I'd stick to /* */ throughout.

> + irs_data = kzalloc(sizeof(*irs_data), GFP_KERNEL);
> + if (!irs_data)
> + return -ENOMEM;
> +
> + // This spinlock is used for SPI config changes
> + raw_spin_lock_init(&irs_data->spi_config_lock);
> +
> + irs_base = ioremap(irs->config_base_address, ACPI_GICV5_IRS_MEM_SIZE);
> + if (!irs_base) {
> + pr_err("Unable to map GIC IRS registers\n");
> + ret = -ENOMEM;
> + goto out_free;
> + }
> +
> + r = gic_request_region(irs->config_base_address, ACPI_GICV5_IRS_MEM_SIZE, "GICv5 IRS");

Really minor but I wonder if this should follow the same ordering as
of_io_request_and_map() which does the request_mem_region() before
trying to ioremap()?

Nice to have the same ordering though that would then put you at odds iwth the
gicv3 redist code that does it in this order. Guess can't win them all and
an ephemeral mapping that is then torn down on error of the second call
doesn't really matter.

> + if (!r) {
> + ret = -EBUSY;
> + goto out_map;
> + }
> +
> + gicv5_irs_init_bases(irs_data, irs_base, NULL, irs->flags & ACPI_MADT_IRS_NON_COHERENT);
> +
> + gicv5_irs_acpi_init_affinity(irs->irs_id, irs_data);
> +
> + ret = gicv5_irs_init(irs_data);
> + if (ret)
> + goto out_release;
> +
> + if (irs_data->spi_range) {
> + pr_info("%s @%llx detected SPI range [%u-%u]\n", "IRS", irs->config_base_address,
> + irs_data->spi_min,
> + irs_data->spi_min +
> + irs_data->spi_range - 1);
> + }
> +
> + return 0;
> +
> +out_release:
> + release_mem_region(r->start, resource_size(r));
> +out_map:
> + iounmap(irs_base);
> +out_free:
> + kfree(irs_data);
> + return ret;
> +}

> diff --git a/drivers/irqchip/irq-gic-v5.c b/drivers/irqchip/irq-gic-v5.c
> index 41ef286c4d78..23fd551c4347 100644
> --- a/drivers/irqchip/irq-gic-v5.c
> +++ b/drivers/irqchip/irq-gic-v5.c
> @@ -579,16 +579,36 @@ static __always_inline int gicv5_irq_domain_translate(struct irq_domain *d,
> unsigned int *type,
> const u8 hwirq_type)
> {
> - if (!is_of_node(fwspec->fwnode))
> - return -EINVAL;
> + unsigned int hwirq_trigger;
> + u8 fwspec_irq_type;
>
> - if (fwspec->param_count < 3)
> - return -EINVAL;
> + if (is_of_node(fwspec->fwnode)) {
>
> - if (fwspec->param[0] != hwirq_type)
> - return -EINVAL;
> + if (fwspec->param_count < 3)
> + return -EINVAL;
>
> - *hwirq = fwspec->param[1];
> + fwspec_irq_type = fwspec->param[0];
> +
> + if (fwspec->param[0] != hwirq_type)
> + return -EINVAL;
> +
> + *hwirq = fwspec->param[1];
> + hwirq_trigger = fwspec->param[2];
> + }
> +
> + if (is_fwnode_irqchip(fwspec->fwnode)) {
> +
> + if (fwspec->param_count != 2)
> + return -EINVAL;
> +
> + fwspec_irq_type = FIELD_GET(GICV5_HWIRQ_TYPE, fwspec->param[0]);
> +
> + if (fwspec_irq_type != hwirq_type)
> + return -EINVAL;
> +
> + *hwirq = FIELD_GET(GICV5_HWIRQ_ID, fwspec->param[0]);
> + hwirq_trigger = fwspec->param[1];
> + }
>
> switch (hwirq_type) {
> case GICV5_HWIRQ_TYPE_PPI:
> @@ -600,7 +620,7 @@ static __always_inline int gicv5_irq_domain_translate(struct irq_domain *d,
> IRQ_TYPE_EDGE_RISING;
> break;
> case GICV5_HWIRQ_TYPE_SPI:
> - *type = fwspec->param[2] & IRQ_TYPE_SENSE_MASK;
> + *type = hwirq_trigger & IRQ_TYPE_SENSE_MASK;
> break;
> default:
> BUILD_BUG_ON(1);
> @@ -660,10 +680,18 @@ static void gicv5_irq_domain_free(struct irq_domain *domain, unsigned int virq,
> static int gicv5_irq_ppi_domain_select(struct irq_domain *d, struct irq_fwspec *fwspec,
> enum irq_domain_bus_token bus_token)
> {
> + u32 hwirq_type;
> +
> if (fwspec->fwnode != d->fwnode)
> return 0;
>
> - if (fwspec->param[0] != GICV5_HWIRQ_TYPE_PPI)
> + if (is_of_node(fwspec->fwnode))
> + hwirq_type = fwspec->param[0];
> +
> + if (is_fwnode_irqchip(fwspec->fwnode))
> + hwirq_type = FIELD_GET(GICV5_HWIRQ_TYPE, fwspec->param[0]);

Bit borderline but maybe worth a helper for getting the irq type from
the fwspec? Or a more generic helper that optionally gets that and the other
stuff you need in gicv5_irq_domain_translate()

> +
> + if (hwirq_type != GICV5_HWIRQ_TYPE_PPI)
> return 0;
>
> return (d == gicv5_global_data.ppi_domain);
> @@ -718,10 +746,18 @@ static int gicv5_irq_spi_domain_alloc(struct irq_domain *domain, unsigned int vi
> static int gicv5_irq_spi_domain_select(struct irq_domain *d, struct irq_fwspec *fwspec,
> enum irq_domain_bus_token bus_token)
> {
> + u32 hwirq_type;
> +
> if (fwspec->fwnode != d->fwnode)
> return 0;
>
> - if (fwspec->param[0] != GICV5_HWIRQ_TYPE_SPI)
> + if (is_of_node(fwspec->fwnode))
> + hwirq_type = fwspec->param[0];
> +
> + if (is_fwnode_irqchip(fwspec->fwnode))
> + hwirq_type = FIELD_GET(GICV5_HWIRQ_TYPE, fwspec->param[0]);
> +
> + if (hwirq_type != GICV5_HWIRQ_TYPE_SPI)
> return 0;
>
> return (d == gicv5_global_data.spi_domain);
> @@ -1082,16 +1118,12 @@ static inline void __init gic_of_setup_kvm_info(struct device_node *node)
> }
> #endif // CONFIG_KVM

Thanks,

Jonathan