[PATCH v8 02/17] ACPI: scan: Add a weak arch_sort_irqchip_probe() to order the IRQCHIP probe

[Sunil V L]

Unlike OF framework, the irqchip probe using IRQCHIP_ACPI_DECLARE has no
order defined. Depending on the Makefile is not a good idea. So,
usually it is worked around by mandating only root interrupt controller
probed using IRQCHIP_ACPI_DECLARE and other interrupt controllers are
probed via cascade mechanism.

However, this is also not a clean solution because if there are multiple
root controllers (ex: RINTC in RISC-V which is per CPU) which need to be
probed first, then the cascade will happen for every root controller.
So, introduce an architecture specific weak function
arch_sort_irqchip_probe() to order the probing of the interrupt
controllers which can be implemented by different architectures as per
their interrupt controller hierarchy.

Signed-off-by: Sunil V L <sunilvl at ventanamicro.com>
Tested-by: Björn Töpel <bjorn at rivosinc.com>
---
 drivers/acpi/scan.c  | 3 +++
 include/linux/acpi.h | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 59771412686b..52a9dfc8e18c 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -2755,6 +2755,8 @@ static int __init acpi_match_madt(union acpi_subtable_headers *header,
 	return 0;
 }
 
+void __weak arch_sort_irqchip_probe(struct acpi_probe_entry *ap_head, int nr) { }
+
 int __init __acpi_probe_device_table(struct acpi_probe_entry *ap_head, int nr)
 {
 	int count = 0;
@@ -2763,6 +2765,7 @@ int __init __acpi_probe_device_table(struct acpi_probe_entry *ap_head, int nr)
 		return 0;
 
 	mutex_lock(&acpi_probe_mutex);
+	arch_sort_irqchip_probe(ap_head, nr);
 	for (ape = ap_head; nr; ape++, nr--) {
 		if (ACPI_COMPARE_NAMESEG(ACPI_SIG_MADT, ape->id)) {
 			acpi_probe_count = 0;
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 0687a442fec7..3fff86f95c2f 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1343,6 +1343,8 @@ struct acpi_probe_entry {
 	kernel_ulong_t driver_data;
 };
 
+void arch_sort_irqchip_probe(struct acpi_probe_entry *ap_head, int nr);
+
 #define ACPI_DECLARE_PROBE_ENTRY(table, name, table_id, subtable,	\
 				 valid, data, fn)			\
 	static const struct acpi_probe_entry __acpi_probe_##name	\
-- 
2.43.0