linux-kernel - [RFC PATCH v2 09/21] ACPI: scan.c: Add weak arch specific function to reorder the IRQCHIP probe

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Date:   Thu, 26 Oct 2023 01:53:32 +0530
From:   Sunil V L <sunilvl@...tanamicro.com>
To:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-acpi@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-serial@...r.kernel.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Anup Patel <anup@...infault.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Atish Kumar Patra <atishp@...osinc.com>,
        Haibo Xu <haibo1.xu@...el.com>,
        Sunil V L <sunilvl@...tanamicro.com>
Subject: [RFC PATCH v2 09/21] ACPI: scan.c: Add weak arch specific function to reorder the IRQCHIP probe

Unlike OF framework, the irqchip probe using IRQCHIP_ACPI_DECLARE has no
order defined. Depending on the driver 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 a architecture specific weak function 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@...tanamicro.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 691d4b7686ee..87f4baebd497 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -2685,6 +2685,8 @@ 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;
@@ -2693,6 +2695,7 @@ 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 afd94c9b8b8a..4ad256a0039c 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1338,6 +1338,8 @@ 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	\
-- 
2.39.2