Re: [PATCH 1/1] i2c: designware: Disable SMBus interrupts to prevent storms from mis-configured firmware

Re: [PATCH 1/1] i2c: designware: Disable SMBus interrupts to prevent storms from mis-configured firmware

[Andy Shevchenko]

On Sat, Oct 11, 2025 at 03:30:57PM +0800, Jinhui Guo wrote:
> When probing the I2C master, disable SMBus interrupts to prevent
> storms caused by broken firmware mis-configuring IC_SMBUS=1; the
> handler never services them and a mis-configured SMBUS Master
> extend-clock timeout can flood the CPU.

...

>  #define DW_IC_TX_ABRT_SOURCE			0x80
>  #define DW_IC_ENABLE_STATUS			0x9c
>  #define DW_IC_CLR_RESTART_DET			0xa8
> +#define DW_IC_SMBUS_INTR_MASK		0xcc

It seems one TAB too little.

>  #define DW_IC_COMP_PARAM_1			0xf4
>  #define DW_IC_COMP_VERSION			0xf8
>  #define DW_IC_SDA_HOLD_MIN_VERS			0x3131312A /* "111*" == v1.11* */

...

The rest LGTM, but let Mika to review.
FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko

[PATCH 0/1] i2c: designware: Fix SMBUS Master interrupts storms

[Jinhui Guo]

Hi all,

We hit interrupt storms on the SMBus master extend-clock timeout IRQ
because broken firmware left IC_SMBUS=1 while the driver IRQ handler
never services SMBus events.

Since we cannot disable IC_SMBUS directly, mask its interrupts to
prevent floods and make the driver more robust.

Thanks,
Jinhui

---
Jinhui Guo (1):
  i2c: designware: Disable SMBus interrupts to prevent storms from
    mis-configured firmware

 drivers/i2c/busses/i2c-designware-core.h   |  1 +
 drivers/i2c/busses/i2c-designware-master.c | 11 +++++++++++
 2 files changed, 12 insertions(+)

-- 
2.20.1

[PATCH 1/1] i2c: designware: Disable SMBus interrupts to prevent storms from mis-configured firmware

[Jinhui Guo]

When probing the I2C master, disable SMBus interrupts to prevent
storms caused by broken firmware mis-configuring IC_SMBUS=1; the
handler never services them and a mis-configured SMBUS Master
extend-clock timeout can flood the CPU.

Signed-off-by: Jinhui Guo <guojinhui.liam@bytedance.com>
---
 drivers/i2c/busses/i2c-designware-core.h   |  1 +
 drivers/i2c/busses/i2c-designware-master.c | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index 347843b4f5dd..d1122ff0a1b7 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -78,6 +78,7 @@
 #define DW_IC_TX_ABRT_SOURCE			0x80
 #define DW_IC_ENABLE_STATUS			0x9c
 #define DW_IC_CLR_RESTART_DET			0xa8
+#define DW_IC_SMBUS_INTR_MASK		0xcc
 #define DW_IC_COMP_PARAM_1			0xf4
 #define DW_IC_COMP_VERSION			0xf8
 #define DW_IC_SDA_HOLD_MIN_VERS			0x3131312A /* "111*" == v1.11* */
diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
index c7a72c28786c..eeb60536da32 100644
--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -997,6 +997,11 @@ static int i2c_dw_init_recovery_info(struct dw_i2c_dev *dev)
 	return 0;
 }
 
+static inline void i2c_dw_disable_smbus_intr(struct dw_i2c_dev *dev)
+{
+	regmap_write(dev->map, DW_IC_SMBUS_INTR_MASK, 0);
+}
+
 int i2c_dw_probe_master(struct dw_i2c_dev *dev)
 {
 	struct i2c_adapter *adap = &dev->adapter;
@@ -1063,6 +1068,12 @@ int i2c_dw_probe_master(struct dw_i2c_dev *dev)
 		return ret;
 
 	__i2c_dw_write_intr_mask(dev, 0);
+	/*
+	 * Mask SMBus interrupts to block storms from broken
+	 * firmware that leaves IC_SMBUS=1; the handler never
+	 * services them.
+	 */
+	i2c_dw_disable_smbus_intr(dev);
 	i2c_dw_release_lock(dev);
 
 	if (!(dev->flags & ACCESS_POLLING)) {
-- 
2.20.1

Re: [PATCH 1/1] i2c: designware: Disable SMBus interrupts to prevent storms from mis-configured firmware

[Andy Shevchenko]

On Sat, Oct 11, 2025 at 03:30:57PM +0800, Jinhui Guo wrote:
> When probing the I2C master, disable SMBus interrupts to prevent
> storms caused by broken firmware mis-configuring IC_SMBUS=1; the
> handler never services them and a mis-configured SMBUS Master
> extend-clock timeout can flood the CPU.

...

>  #define DW_IC_TX_ABRT_SOURCE			0x80
>  #define DW_IC_ENABLE_STATUS			0x9c
>  #define DW_IC_CLR_RESTART_DET			0xa8
> +#define DW_IC_SMBUS_INTR_MASK		0xcc

It seems one TAB too little.

>  #define DW_IC_COMP_PARAM_1			0xf4
>  #define DW_IC_COMP_VERSION			0xf8
>  #define DW_IC_SDA_HOLD_MIN_VERS			0x3131312A /* "111*" == v1.11* */

...

The rest LGTM, but let Mika to review.
FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/1] i2c: designware: Disable SMBus interrupts to prevent storms from mis-configured firmware

[Mika Westerberg]

Hi,

On Sat, Oct 11, 2025 at 03:30:57PM +0800, Jinhui Guo wrote:
> When probing the I2C master, disable SMBus interrupts to prevent
> storms caused by broken firmware mis-configuring IC_SMBUS=1; the
> handler never services them and a mis-configured SMBUS Master
> extend-clock timeout can flood the CPU.
> 
> Signed-off-by: Jinhui Guo <guojinhui.liam@bytedance.com>
> ---
>  drivers/i2c/busses/i2c-designware-core.h   |  1 +
>  drivers/i2c/busses/i2c-designware-master.c | 11 +++++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
> index 347843b4f5dd..d1122ff0a1b7 100644
> --- a/drivers/i2c/busses/i2c-designware-core.h
> +++ b/drivers/i2c/busses/i2c-designware-core.h
> @@ -78,6 +78,7 @@
>  #define DW_IC_TX_ABRT_SOURCE			0x80
>  #define DW_IC_ENABLE_STATUS			0x9c
>  #define DW_IC_CLR_RESTART_DET			0xa8
> +#define DW_IC_SMBUS_INTR_MASK		0xcc
>  #define DW_IC_COMP_PARAM_1			0xf4
>  #define DW_IC_COMP_VERSION			0xf8
>  #define DW_IC_SDA_HOLD_MIN_VERS			0x3131312A /* "111*" == v1.11* */
> diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
> index c7a72c28786c..eeb60536da32 100644
> --- a/drivers/i2c/busses/i2c-designware-master.c
> +++ b/drivers/i2c/busses/i2c-designware-master.c
> @@ -997,6 +997,11 @@ static int i2c_dw_init_recovery_info(struct dw_i2c_dev *dev)
>  	return 0;
>  }
>  
> +static inline void i2c_dw_disable_smbus_intr(struct dw_i2c_dev *dev)
> +{
> +	regmap_write(dev->map, DW_IC_SMBUS_INTR_MASK, 0);
> +}

I wonder instead of this wrapper, can you just do this in
i2c_dw_init_master() right after the adapter has been disabled?

> +
>  int i2c_dw_probe_master(struct dw_i2c_dev *dev)
>  {
>  	struct i2c_adapter *adap = &dev->adapter;
> @@ -1063,6 +1068,12 @@ int i2c_dw_probe_master(struct dw_i2c_dev *dev)
>  		return ret;
>  
>  	__i2c_dw_write_intr_mask(dev, 0);
> +	/*
> +	 * Mask SMBus interrupts to block storms from broken
> +	 * firmware that leaves IC_SMBUS=1; the handler never
> +	 * services them.
> +	 */
> +	i2c_dw_disable_smbus_intr(dev);
>  	i2c_dw_release_lock(dev);
>  
>  	if (!(dev->flags & ACCESS_POLLING)) {
> -- 
> 2.20.1

Re: [PATCH 1/1] i2c: designware: Disable SMBus interrupts to prevent storms from mis-configured firmware

[Jinhui Guo]

Hi,

On Mon, Oct 20, 2025 12:29:58 +0200, Mika Westerberg wrote:
> > +static inline void i2c_dw_disable_smbus_intr(struct dw_i2c_dev *dev)
> > +{
> > +	regmap_write(dev->map, DW_IC_SMBUS_INTR_MASK, 0);
> > +}

> I wonder instead of this wrapper, can you just do this in
> i2c_dw_init_master() right after the adapter has been disabled?

We can do that to simplify the code. Patch v2 is sent and has been tested.
https://lore.kernel.org/all/20251021072431.3427-1-guojinhui.liam@bytedance.com/

Thanks,
Jinhui