hw/m68k/q800: Don't connect two qemu_irqs directly to the same input

The q800 board code connects both of the IRQ outputs of the ESCC
to the same pic[3] qemu_irq. Connecting two qemu_irqs outputs directly
to the same input is not valid as it produces subtly wrong behaviour
(for instance if both the IRQ lines are high, and then one goes
low, the PIC input will see this as a high-to-low transition
even though the second IRQ line should still be holding it high).

This kind of wiring needs an explicitly created OR gate; add one.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20201106235109.7066-2-peter.maydell@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

diff --git a/hw/m68k/Kconfig b/hw/m68k/Kconfig
index c757e7dfa48bbbaba9cfa4676cc2acf53cbf972c..60d7bcfb8f2be9c0dba7fca1838603dbf20a0bed 100644 (file)
--- a/hw/m68k/Kconfig
+++ b/hw/m68k/Kconfig
@@ -22,3 +22,4 @@ config Q800
     select ESCC
     select ESP
     select DP8393X
+    select OR_IRQ

diff --git a/hw/m68k/q800.c b/hw/m68k/q800.c
index 4db2b9bbc7b4dd46b7757655c1f1dc9412f5b408..f9a2be776eb03766471ea46df27d593f0bba1621 100644 (file)
--- a/hw/m68k/q800.c
+++ b/hw/m68k/q800.c
@@ -29,6 +29,7 @@
 #include "hw/hw.h"
 #include "hw/boards.h"
 #include "hw/irq.h"
+#include "hw/or-irq.h"
 #include "elf.h"
 #include "hw/loader.h"
 #include "ui/console.h"
@@ -173,6 +174,7 @@ static void q800_init(MachineState *machine)
     CPUState *cs;
     DeviceState *dev;
     DeviceState *via_dev;
+    DeviceState *escc_orgate;
     SysBusESPState *sysbus_esp;
     ESPState *esp;
     SysBusDevice *sysbus;
@@ -285,8 +287,14 @@ static void q800_init(MachineState *machine)
     qdev_prop_set_uint32(dev, "chnAtype", 0);
     sysbus = SYS_BUS_DEVICE(dev);
     sysbus_realize_and_unref(sysbus, &error_fatal);
-    sysbus_connect_irq(sysbus, 0, pic[3]);
-    sysbus_connect_irq(sysbus, 1, pic[3]);
+
+    /* Logically OR both its IRQs together */
+    escc_orgate = DEVICE(object_new(TYPE_OR_IRQ));
+    object_property_set_int(OBJECT(escc_orgate), "num-lines", 2, &error_fatal);
+    qdev_realize_and_unref(escc_orgate, NULL, &error_fatal);
+    sysbus_connect_irq(sysbus, 0, qdev_get_gpio_in(escc_orgate, 0));
+    sysbus_connect_irq(sysbus, 1, qdev_get_gpio_in(escc_orgate, 1));
+    qdev_connect_gpio_out(DEVICE(escc_orgate), 0, pic[3]);
     sysbus_mmio_map(sysbus, 0, SCC_BASE);
 
     /* SCSI */