[PATCH V2] irqchip: Make irqchip_init() usable on pure ACPI systems

[Huacai Chen <chenhuacai@loongson.cn>]

Pure ACPI system (e.g., LoongArch) doesn't select OF and OF_IRQ, but it
still need a non-empty irqchip_init(). So, change the IRQCHIP dependency
from OF_IRQ to (OF_IRQ || ACPI_GENERIC_GSI), and then define an empty
inline of_irq_init() in the !CONFIG_OF_IRQ case, so as to make the non-
empty irqchip_init() be usable on pure ACPI systems.

Without this patch we get such errors:

[    0.000000] NR_IRQS: 576, nr_irqs: 576, preallocated irqs: 16
[    0.000000] Kernel panic - not syncing: IPI IRQ mapping failed
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.0.0-rc6+ #2189
[    0.000000] Hardware name: Loongson Loongson-3A5000-7A1000-1w-CRB/Loongson-LS3A5000-7A1000-1w-CRB, BIOS vUDK2018-LoongArch-V2.0.pre-beta8 08/18/2022
[    0.000000] Stack : 0000000000000000 9000000000fa4388 900000000140c000 900000000140fb70
[    0.000000]         0000000000000000 900000000140fb70 90000000012f4aa0 900000000140fa98
[    0.000000]         900000000140fa0c 900000008140f9ff 0000000000000030 0000000000000005
[    0.000000]         900000000578f708 0000000004750000 0000000000000000 00000000ffffdfff
[    0.000000]         0000000000000000 0000000000000000 0000000000000030 000000000000002f
[    0.000000]         900000000141f000 0000000004750000 9000000001427348 00000000000000b0
[    0.000000]         90000000012f4aa0 0000000000000004 0000000000000000 9000000001020000
[    0.000000]         9000000005781b80 9000000005781ba9 0000000000000000 9000000001315e30
[    0.000000]         900000000129a3b0 9000000000222b64 0000000000000000 00000000000000b0
[    0.000000]         0000000000000004 0000000000000000 0000000000070000 0000000000000800
[    0.000000]         ...
[    0.000000] Call Trace:
[    0.000000] [<9000000000222b64>] show_stack+0x24/0x124
[    0.000000] [<9000000000fa4388>] dump_stack_lvl+0x60/0x88
[    0.000000] [<9000000000f9965c>] panic+0x130/0x2f8
[    0.000000] [<9000000000fd4324>] init_IRQ+0xa8/0x240
[    0.000000] [<9000000000fd0b38>] start_kernel+0x488/0x5f0
[    0.000000] [<9000000000fb10c4>] kernel_entry+0xc4/0xc8
[    0.000000]
[    0.000000] ---[ end Kernel panic - not syncing: IPI IRQ mapping failed ]---

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/irqchip/Kconfig   | 2 +-
 include/linux/of_irq.h    | 6 ++++--
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 66b9fa408bf2..93ad04d58f17 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -3,7 +3,7 @@ menu "IRQ chip support"
 
 config IRQCHIP
 	def_bool y
-	depends on OF_IRQ
+	depends on (OF_IRQ || ACPI_GENERIC_GSI)
 
 config ARM_GIC
 	bool
diff --git a/include/linux/of_irq.h b/include/linux/of_irq.h
index 83fccd0c9bba..d6d3eae2f145 100644
--- a/include/linux/of_irq.h
+++ b/include/linux/of_irq.h
@@ -37,9 +37,8 @@ extern unsigned int irq_create_of_mapping(struct of_phandle_args *irq_data);
 extern int of_irq_to_resource(struct device_node *dev, int index,
 			      struct resource *r);
 
-extern void of_irq_init(const struct of_device_id *matches);
-
 #ifdef CONFIG_OF_IRQ
+extern void of_irq_init(const struct of_device_id *matches);
 extern int of_irq_parse_one(struct device_node *device, int index,
 			  struct of_phandle_args *out_irq);
 extern int of_irq_count(struct device_node *dev);
@@ -57,6 +56,9 @@ extern struct irq_domain *of_msi_map_get_device_domain(struct device *dev,
 extern void of_msi_configure(struct device *dev, struct device_node *np);
 u32 of_msi_map_id(struct device *dev, struct device_node *msi_np, u32 id_in);
 #else
+static inline void of_irq_init(const struct of_device_id *matches)
+{
+}
 static inline int of_irq_parse_one(struct device_node *device, int index,
 				   struct of_phandle_args *out_irq)
 {
-- 
2.31.1