hw/arm/musicpal: Don't connect two qemu_irqs directly to the same input

The MusicPal board code connects both of the IRQ outputs of the UART
to the same INTC 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 INTC 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.

Inspired-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20201107193403.436146-5-f4bug@amsat.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/Kconfig

@@ -93,6 +93,7 @@ config MUSCA
 
 config MUSICPAL
     bool
+    select OR_IRQ
     select BITBANG_I2C
     select MARVELL_88W8618
     select PTIMER

hw/arm/musicpal.c

@@ -27,6 +27,7 @@
 #include "ui/console.h"
 #include "hw/i2c/i2c.h"
 #include "hw/irq.h"
+#include "hw/or-irq.h"
 #include "hw/audio/wm8750.h"
 #include "sysemu/block-backend.h"
 #include "sysemu/runstate.h"
@@ -77,8 +78,7 @@
 #define MP_TIMER4_IRQ           7
 #define MP_EHCI_IRQ             8
 #define MP_ETH_IRQ              9
-#define MP_UART1_IRQ            11
-#define MP_UART2_IRQ            11
+#define MP_UART_SHARED_IRQ      11
 #define MP_GPIO_IRQ             12
 #define MP_RTC_IRQ              28
 #define MP_AUDIO_IRQ            30
@@ -1589,6 +1589,7 @@ static void musicpal_init(MachineState *machine)
     ARMCPU *cpu;
     qemu_irq pic[32];
     DeviceState *dev;
+    DeviceState *uart_orgate;
     DeviceState *i2c_dev;
     DeviceState *lcd_dev;
     DeviceState *key_dev;
@@ -1627,9 +1628,17 @@ static void musicpal_init(MachineState *machine)
                           pic[MP_TIMER2_IRQ], pic[MP_TIMER3_IRQ],
                           pic[MP_TIMER4_IRQ], NULL);
 
-    serial_mm_init(address_space_mem, MP_UART1_BASE, 2, pic[MP_UART1_IRQ],
+    /* Logically OR both UART IRQs together */
+    uart_orgate = DEVICE(object_new(TYPE_OR_IRQ));
+    object_property_set_int(OBJECT(uart_orgate), "num-lines", 2, &error_fatal);
+    qdev_realize_and_unref(uart_orgate, NULL, &error_fatal);
+    qdev_connect_gpio_out(DEVICE(uart_orgate), 0, pic[MP_UART_SHARED_IRQ]);
+
+    serial_mm_init(address_space_mem, MP_UART1_BASE, 2,
+                   qdev_get_gpio_in(uart_orgate, 0),
                    1825000, serial_hd(0), DEVICE_NATIVE_ENDIAN);
-    serial_mm_init(address_space_mem, MP_UART2_BASE, 2, pic[MP_UART2_IRQ],
+    serial_mm_init(address_space_mem, MP_UART2_BASE, 2,
+                   qdev_get_gpio_in(uart_orgate, 1),
                    1825000, serial_hd(1), DEVICE_NATIVE_ENDIAN);
 
     /* Register flash */