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

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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>
This commit is contained in:
Peter Maydell 2020-11-06 23:51:08 +00:00 committed by Laurent Vivier
parent ad717e6da3
commit 9526486164
2 changed files with 11 additions and 2 deletions
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1
hw/m68k/Kconfig
View file

@ -22,3 +22,4 @@ config Q800
select ESCC
select ESP
select DP8393X
select OR_IRQ

12
hw/m68k/q800.c
View file

@ -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 */