We create an OR gate to wire together the overflow IRQs for all the
UARTs on the board; this has to have twice the number of inputs as
there are UARTs, since each UART feeds it a TX overflow and an RX
overflow interrupt line.  Replace the hardcoded '10' with a
calculation based on the size of the uart[] array in the
MPS2TZMachineState.  (We rely on OR gate inputs that are never wired
up or asserted being treated as always-zero.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/arm/mps2-tz.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/hw/arm/mps2-tz.c b/hw/arm/mps2-tz.c
index 014ba775783..f1a9c5f65a5 100644
--- a/hw/arm/mps2-tz.c
+++ b/hw/arm/mps2-tz.c
@@ -516,13 +516,18 @@ static void mps2tz_common_init(MachineState *machine)
      */
     memory_region_add_subregion(system_memory, 0x80000000, machine->ram);
 
-    /* The overflow IRQs for all UARTs are ORed together.
+    /*
+     * The overflow IRQs for all UARTs are ORed together.
      * Tx, Rx and "combined" IRQs are sent to the NVIC separately.
-     * Create the OR gate for this.
+     * Create the OR gate for this: it has one input for the TX overflow
+     * and one for the RX overflow for each UART we might have.
+     * (If the board has fewer than the maximum possible number of UARTs
+     * those inputs are never wired up and are treated as always-zero.)
      */
     object_initialize_child(OBJECT(mms), "uart-irq-orgate",
                             &mms->uart_irq_orgate, TYPE_OR_IRQ);
-    object_property_set_int(OBJECT(&mms->uart_irq_orgate), "num-lines", 10,
+    object_property_set_int(OBJECT(&mms->uart_irq_orgate), "num-lines",
+                            2 * ARRAY_SIZE(mms->uart),
                             &error_fatal);
     qdev_realize(DEVICE(&mms->uart_irq_orgate), NULL, &error_fatal);
     qdev_connect_gpio_out(DEVICE(&mms->uart_irq_orgate), 0,
-- 
2.20.1

On 2/15/21 3:51 AM, Peter Maydell wrote:
> We create an OR gate to wire together the overflow IRQs for all the
> UARTs on the board; this has to have twice the number of inputs as
> there are UARTs, since each UART feeds it a TX overflow and an RX
> overflow interrupt line.  Replace the hardcoded '10' with a
> calculation based on the size of the uart[] array in the
> MPS2TZMachineState.  (We rely on OR gate inputs that are never wired
> up or asserted being treated as always-zero.)
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
>   hw/arm/mps2-tz.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

On 2/15/21 12:51 PM, Peter Maydell wrote:
> We create an OR gate to wire together the overflow IRQs for all the
> UARTs on the board; this has to have twice the number of inputs as
> there are UARTs, since each UART feeds it a TX overflow and an RX
> overflow interrupt line.  Replace the hardcoded '10' with a
> calculation based on the size of the uart[] array in the
> MPS2TZMachineState.  (We rely on OR gate inputs that are never wired
> up or asserted being treated as always-zero.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/arm/mps2-tz.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>