[v2] hw/arm/bcm2838: Route I2C interrupts to GIC

[PATCH v2] hw/arm/bcm2838: Route I2C interrupts to GIC

Posted by Nicholas Righi 1 month ago

The I2C interrupts are only routed to the legacy interrupt controller. This means
that for modern device trees that use the GIC, the interrupts don't work. This patch
adds a splitter to route the I2C interrupt to both the legacy interrupt controller and the GIC.

Testing

Add these lines to QEMU invocation

-drive if=none,id=i2c_storage,format=raw,file=eeprom.bin \
-device at24c-eeprom,bus=i2c-bus.1,address=0x50,drive=i2c_storage,rom-size=4096 \

note: eeprom.bin is all zeros

Before this change, running i2c get to read from EEPROM would result in this

i2cget -y 1 0x50
Error: Read failed

After this change, running i2c to read from EEPROM results in this

i2cget -y 1 0x50
0x00

The eeprom can now also be enabled in the device tree. Before the
eeprom driver load would fail due to the read failing

ls -l /sys/bus/i2c/devices/i2c-1/1-0050/ | grep -i eeprom
-rw------- 1 root root 4096 May 17 16:57 eeprom

Signed-off-by: Nicholas Righi <nicholasrighi@gmail.com>
---
Changes v1 -> v2:
    - Use a splitter to route the OR gated i2c interrupt to both the
      legacy interrupt controller and the GIC, instead of just replacing
      the legacy routing with the GIC routing
---
 hw/arm/bcm2835_peripherals.c         | 9 +++++++++
 hw/arm/bcm2838.c                     | 4 ++++
 include/hw/arm/bcm2835_peripherals.h | 2 ++
 include/hw/arm/bcm2838_peripherals.h | 1 +
 4 files changed, 16 insertions(+)

diff --git a/hw/arm/bcm2835_peripherals.c b/hw/arm/bcm2835_peripherals.c
index 8a1e72dfab..558c180df9 100644
--- a/hw/arm/bcm2835_peripherals.c
+++ b/hw/arm/bcm2835_peripherals.c
@@ -179,6 +179,8 @@ static void raspi_peripherals_base_init(Object *obj)
                             &s->orgated_i2c_irq, TYPE_OR_IRQ);
     object_property_set_int(OBJECT(&s->orgated_i2c_irq), "num-lines",
                             ORGATED_I2C_IRQ_COUNT, &error_abort);
+    object_initialize_child(obj, "orgated-i2c-irq-splitter",
+                            &s->orgated_i2c_irq_splitter, TYPE_SPLIT_IRQ);
 }
 
 static void bcm2835_peripherals_realize(DeviceState *dev, Error **errp)
@@ -504,7 +506,14 @@ void bcm_soc_peripherals_common_realize(DeviceState *dev, Error **errp)
         sysbus_connect_irq(SYS_BUS_DEVICE(&s->i2c[n]), 0,
                            qdev_get_gpio_in(DEVICE(&s->orgated_i2c_irq), n));
     }
+
+    qdev_prop_set_uint32(DEVICE(&s->orgated_i2c_irq_splitter), "num-lines", 2);
+    if (!qdev_realize(DEVICE(&s->orgated_i2c_irq_splitter), NULL, errp)) {
+        return;
+    }
     qdev_connect_gpio_out(DEVICE(&s->orgated_i2c_irq), 0,
+                          qdev_get_gpio_in(DEVICE(&s->orgated_i2c_irq_splitter), 0));
+    qdev_connect_gpio_out(DEVICE(&s->orgated_i2c_irq_splitter), 0,
                           qdev_get_gpio_in_named(DEVICE(&s->ic),
                                                  BCM2835_IC_GPU_IRQ,
                                                  INTERRUPT_I2C));
diff --git a/hw/arm/bcm2838.c b/hw/arm/bcm2838.c
index c14a854046..089af412a3 100644
--- a/hw/arm/bcm2838.c
+++ b/hw/arm/bcm2838.c
@@ -184,6 +184,10 @@ static void bcm2838_realize(DeviceState *dev, Error **errp)
     sysbus_connect_irq(SYS_BUS_DEVICE(&ps_base->aux), 0,
                        qdev_get_gpio_in(gicdev, GIC_SPI_INTERRUPT_AUX_UART1));
 
+    /* Connect the I2C interrupt to the interrupt controller */
+    qdev_connect_gpio_out(DEVICE(&ps_base->orgated_i2c_irq_splitter), 1,
+                          qdev_get_gpio_in(gicdev, GIC_SPI_INTERRUPT_I2C));
+
     /* Connect VC mailbox to the interrupt controller */
     sysbus_connect_irq(SYS_BUS_DEVICE(&ps_base->mboxes), 0,
                        qdev_get_gpio_in(gicdev, GIC_SPI_INTERRUPT_MBOX));
diff --git a/include/hw/arm/bcm2835_peripherals.h b/include/hw/arm/bcm2835_peripherals.h
index bf35bb18e5..4f356f4643 100644
--- a/include/hw/arm/bcm2835_peripherals.h
+++ b/include/hw/arm/bcm2835_peripherals.h
@@ -33,6 +33,7 @@
 #include "hw/usb/hcd-dwc2.h"
 #include "hw/ssi/bcm2835_spi.h"
 #include "hw/i2c/bcm2835_i2c.h"
+#include "hw/core/split-irq.h"
 #include "hw/nvram/bcm2835_otp.h"
 #include "hw/misc/unimp.h"
 #include "qom/object.h"
@@ -72,6 +73,7 @@ struct BCMSocPeripheralBaseState {
     BCM2835SPIState spi[1];
     BCM2835I2CState i2c[3];
     OrIRQState orgated_i2c_irq;
+    SplitIRQ orgated_i2c_irq_splitter;
     BCM2835OTPState otp;
     UnimplementedDeviceState dbus;
     UnimplementedDeviceState ave0;
diff --git a/include/hw/arm/bcm2838_peripherals.h b/include/hw/arm/bcm2838_peripherals.h
index 7ee1bd066f..0be97e67c7 100644
--- a/include/hw/arm/bcm2838_peripherals.h
+++ b/include/hw/arm/bcm2838_peripherals.h
@@ -22,6 +22,7 @@
 #define GIC_SPI_INTERRUPT_DMA_7_8      87
 #define GIC_SPI_INTERRUPT_DMA_9_10     88
 #define GIC_SPI_INTERRUPT_AUX_UART1    93
+#define GIC_SPI_INTERRUPT_I2C          117
 #define GIC_SPI_INTERRUPT_SDHOST       120
 #define GIC_SPI_INTERRUPT_UART0        121
 #define GIC_SPI_INTERRUPT_RNG200       125
-- 
2.54.0

Re: [PATCH v2] hw/arm/bcm2838: Route I2C interrupts to GIC

Posted by Peter Maydell 3 weeks, 3 days ago

On Tue, 9 Jun 2026 at 03:40, Nicholas Righi <nicholasrighi@gmail.com> wrote:
>
> The I2C interrupts are only routed to the legacy interrupt controller. This means
> that for modern device trees that use the GIC, the interrupts don't work. This patch
> adds a splitter to route the I2C interrupt to both the legacy interrupt controller and the GIC.
>
> Testing
>
> Add these lines to QEMU invocation
>
> -drive if=none,id=i2c_storage,format=raw,file=eeprom.bin \
> -device at24c-eeprom,bus=i2c-bus.1,address=0x50,drive=i2c_storage,rom-size=4096 \
>
> note: eeprom.bin is all zeros
>
> Before this change, running i2c get to read from EEPROM would result in this
>
> i2cget -y 1 0x50
> Error: Read failed
>
> After this change, running i2c to read from EEPROM results in this
>
> i2cget -y 1 0x50
> 0x00
>
> The eeprom can now also be enabled in the device tree. Before the
> eeprom driver load would fail due to the read failing
>
> ls -l /sys/bus/i2c/devices/i2c-1/1-0050/ | grep -i eeprom
> -rw------- 1 root root 4096 May 17 16:57 eeprom
>
> Signed-off-by: Nicholas Righi <nicholasrighi@gmail.com>
> ---
> Changes v1 -> v2:
>     - Use a splitter to route the OR gated i2c interrupt to both the
>       legacy interrupt controller and the GIC, instead of just replacing
>       the legacy routing with the GIC routing
> ---
>  hw/arm/bcm2835_peripherals.c         | 9 +++++++++
>  hw/arm/bcm2838.c                     | 4 ++++
>  include/hw/arm/bcm2835_peripherals.h | 2 ++
>  include/hw/arm/bcm2838_peripherals.h | 1 +
>  4 files changed, 16 insertions(+)



Applied to target-arm.next, thanks.

-- PMM

Re: [PATCH v2] hw/arm/bcm2838: Route I2C interrupts to GIC

Posted by Philippe Mathieu-Daudé 3 weeks, 3 days ago

On 16/6/26 13:10, Peter Maydell wrote:
> On Tue, 9 Jun 2026 at 03:40, Nicholas Righi <nicholasrighi@gmail.com> wrote:
>>
>> The I2C interrupts are only routed to the legacy interrupt controller. This means
>> that for modern device trees that use the GIC, the interrupts don't work. This patch
>> adds a splitter to route the I2C interrupt to both the legacy interrupt controller and the GIC.
>>
>> Testing
>>
>> Add these lines to QEMU invocation
>>
>> -drive if=none,id=i2c_storage,format=raw,file=eeprom.bin \
>> -device at24c-eeprom,bus=i2c-bus.1,address=0x50,drive=i2c_storage,rom-size=4096 \
>>
>> note: eeprom.bin is all zeros
>>
>> Before this change, running i2c get to read from EEPROM would result in this
>>
>> i2cget -y 1 0x50
>> Error: Read failed
>>
>> After this change, running i2c to read from EEPROM results in this
>>
>> i2cget -y 1 0x50
>> 0x00
>>
>> The eeprom can now also be enabled in the device tree. Before the
>> eeprom driver load would fail due to the read failing
>>
>> ls -l /sys/bus/i2c/devices/i2c-1/1-0050/ | grep -i eeprom
>> -rw------- 1 root root 4096 May 17 16:57 eeprom
>>
>> Signed-off-by: Nicholas Righi <nicholasrighi@gmail.com>
>> ---
>> Changes v1 -> v2:
>>      - Use a splitter to route the OR gated i2c interrupt to both the
>>        legacy interrupt controller and the GIC, instead of just replacing
>>        the legacy routing with the GIC routing
>> ---
>>   hw/arm/bcm2835_peripherals.c         | 9 +++++++++
>>   hw/arm/bcm2838.c                     | 4 ++++
>>   include/hw/arm/bcm2835_peripherals.h | 2 ++
>>   include/hw/arm/bcm2838_peripherals.h | 1 +
>>   4 files changed, 16 insertions(+)
> 
> 
> 
> Applied to target-arm.next, thanks.

Too late but still it was in my review queue:
Reviewed-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>

Re: [PATCH v2] hw/arm/bcm2838: Route I2C interrupts to GIC

Posted by Peter Maydell 3 weeks, 3 days ago

On Tue, 16 Jun 2026 at 15:59, Philippe Mathieu-Daudé
<philmd@oss.qualcomm.com> wrote:
>
> On 16/6/26 13:10, Peter Maydell wrote:
> > On Tue, 9 Jun 2026 at 03:40, Nicholas Righi <nicholasrighi@gmail.com> wrote:
> >>
> >> The I2C interrupts are only routed to the legacy interrupt controller. This means
> >> that for modern device trees that use the GIC, the interrupts don't work. This patch
> >> adds a splitter to route the I2C interrupt to both the legacy interrupt controller and the G

> > Applied to target-arm.next, thanks.
>
> Too late but still it was in my review queue:
> Reviewed-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>

I haven't done anything with my queue yet, so I've added your R-by tag;
thanks!

-- PMM