[PATCH v2 3/3] [NOT-FOR-UPSTREAM] platform: generic: virt: add APLIC M-mode IRQ test overlay

[Raymond Mao <raymondmaoca@gmail.com>]

From: Raymond Mao <raymond.mao@riscstar.com>

Stock QEMU virt,aia=aplic delegates all wired IRQs from the M-mode
APLIC to its child S-mode APLIC, which prevents the local
APLIC_QEMU_WIRED_TEST path from exercising M-mode wired IRQ delivery.

Add a DT overlay that changes the M-mode APLIC delegation ranges from
1..96 to 1..9 and 11..96, leaving hwirq 10 local to the M-mode APLIC.
This matches the local test path, which uses UART RX on hwirq 10.

The overlay is intended to be applied on top of a base DTB dumped from
the same QEMU virt,aia=aplic command line, so the embedded child
phandle matches that dumped base DTB.

Usage:
- dump the base DTB from the target QEMU command line
- compile this file as a DT overlay and apply it to the dumped base DTB
- boot QEMU with the merged DTB and APLIC_QEMU_WIRED_TEST=y to verify
  M-mode wired IRQ delivery

Signed-off-by: Raymond Mao <raymond.mao@riscstar.com>
---
 .../virt/aplic_mmode_wired_irq_test.dts       | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)
 create mode 100644 platform/generic/virt/aplic_mmode_wired_irq_test.dts

diff --git a/platform/generic/virt/aplic_mmode_wired_irq_test.dts b/platform/generic/virt/aplic_mmode_wired_irq_test.dts
new file mode 100644
index 00000000..8fb976b5
--- /dev/null
+++ b/platform/generic/virt/aplic_mmode_wired_irq_test.dts
@@ -0,0 +1,28 @@
+/dts-v1/;
+/plugin/;
+
+/ {
+	fragment@0 {
+		target-path = "/soc/interrupt-controller@c000000";
+		__overlay__ {
+			/*
+			 * Stock QEMU virt,aia=aplic delegates all wired IRQs from
+			 * the M-mode APLIC to its child S-mode APLIC:
+			 *
+			 *   <child-phandle 1 96>
+			 *
+			 * Keep hwirq 10 local to the M-mode APLIC by delegating
+			 * only 1..9 and 11..96 to the child APLIC. This matches
+			 * the local OpenSBI APLIC_QEMU_WIRED_TEST path, which
+			 * exercises wired IRQ delivery via hwirq 10 (UART RX).
+			 *
+			 * This overlay is intended to be applied on top of a base
+			 * DTB dumped from the same QEMU virt,aia=aplic command
+			 * line. The child phandle value below therefore matches
+			 * that dumped base DTB.
+			 */
+			riscv,delegate = <0x04 0x01 0x09 0x04 0x0b 0x60>;
+			riscv,delegation = <0x04 0x01 0x09 0x04 0x0b 0x60>;
+		};
+	};
+};
-- 
2.25.1


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