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

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Message-ID: <20251020102958.GL2912318@black.igk.intel.com>
Date: Mon, 20 Oct 2025 12:29:58 +0200
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: Jinhui Guo <guojinhui.liam@...edance.com>
Cc: andriy.shevchenko@...ux.intel.com, jsd@...ihalf.com,
	andi.shyti@...nel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] i2c: designware: Disable SMBus interrupts to prevent
 storms from mis-configured firmware

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@...edance.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