From: Bernhard Beschow <shentey@gmail.com>

Commit 56b1f50e3c10 ("hw/i386/pc: Wire RTC ISA IRQs in south bridges")
attempted to refactor RTC IRQ wiring which was previously done in
pc_basic_device_init() but forgot about the isapc machine. Fix this by
wiring in the code section dedicated exclusively to the isapc machine.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2961
Fixes: 56b1f50e3c10 ("hw/i386/pc: Wire RTC ISA IRQs in south bridges")
cc: qemu-stable
Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
Message-Id: <20250526203820.1853-1-shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 0b006153b7ec66505cb2d231235aa19ca5d2ce37)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 6c91e2d292..7cfa142b11 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -285,6 +285,8 @@ static void pc_init1(MachineState *machine, const char *pci_type)
         pcms->idebus[0] = qdev_get_child_bus(dev, "ide.0");
         pcms->idebus[1] = qdev_get_child_bus(dev, "ide.1");
     } else {
+        uint32_t irq;
+
         isa_bus = isa_bus_new(NULL, system_memory, system_io,
                               &error_abort);
         isa_bus_register_input_irqs(isa_bus, x86ms->gsi);
@@ -292,6 +294,9 @@ static void pc_init1(MachineState *machine, const char *pci_type)
         x86ms->rtc = isa_new(TYPE_MC146818_RTC);
         qdev_prop_set_int32(DEVICE(x86ms->rtc), "base_year", 2000);
         isa_realize_and_unref(x86ms->rtc, isa_bus, &error_fatal);
+        irq = object_property_get_uint(OBJECT(x86ms->rtc), "irq",
+                                       &error_fatal);
+        isa_connect_gpio_out(ISA_DEVICE(x86ms->rtc), 0, irq);
 
         i8257_dma_init(OBJECT(machine), isa_bus, 0);
         pcms->hpet_enabled = false;
-- 
2.47.2