Re: [PATCH] i2c: altera: Fix race between xfer_msg and isr thread

[Thor Thayer <thor.thayer@linux.intel.com>]

On 4/9/20 8:06 PM, Atsushi Nemoto wrote:
> Use a mutex to protect access to idev->msg_len, idev->buf, etc. which
> are modified by both altr_i2c_xfer_msg() and altr_i2c_isr().
> 
> Signed-off-by: Atsushi Nemoto <atsushi.nemoto@sord.co.jp>
> ---

Acked-by: Thor Thayer <thor.thayer@linux.intel.com>

>   drivers/i2c/busses/i2c-altera.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-altera.c b/drivers/i2c/busses/i2c-altera.c
> index 20ef63820c77..3db7d77c5a1e 100644
> --- a/drivers/i2c/busses/i2c-altera.c
> +++ b/drivers/i2c/busses/i2c-altera.c
> @@ -70,6 +70,7 @@
>    * @isr_mask: cached copy of local ISR enables.
>    * @isr_status: cached copy of local ISR status.
>    * @lock: spinlock for IRQ synchronization.
> + * @mutex: mutex for IRQ thread.
>    */
>   struct altr_i2c_dev {
>   	void __iomem *base;
> @@ -86,6 +87,7 @@ struct altr_i2c_dev {
>   	u32 isr_mask;
>   	u32 isr_status;
>   	spinlock_t lock;	/* IRQ synchronization */
> +	struct mutex mutex;
>   };
>   
>   static void
> @@ -245,10 +247,11 @@ static irqreturn_t altr_i2c_isr(int irq, void *_dev)
>   	struct altr_i2c_dev *idev = _dev;
>   	u32 status = idev->isr_status;
>   
> +	mutex_lock(&idev->mutex);
>   	if (!idev->msg) {
>   		dev_warn(idev->dev, "unexpected interrupt\n");
>   		altr_i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
> -		return IRQ_HANDLED;
> +		goto out;
>   	}
>   	read = (idev->msg->flags & I2C_M_RD) != 0;
>   
> @@ -301,6 +304,8 @@ static irqreturn_t altr_i2c_isr(int irq, void *_dev)
>   		complete(&idev->msg_complete);
>   		dev_dbg(idev->dev, "Message Complete\n");
>   	}
> +out:
> +	mutex_unlock(&idev->mutex);
>   
>   	return IRQ_HANDLED;
>   }
> @@ -312,6 +317,7 @@ static int altr_i2c_xfer_msg(struct altr_i2c_dev *idev, struct i2c_msg *msg)
>   	u32 value;
>   	u8 addr = i2c_8bit_addr_from_msg(msg);
>   
> +	mutex_lock(&idev->mutex);
>   	idev->msg = msg;
>   	idev->msg_len = msg->len;
>   	idev->buf = msg->buf;
> @@ -336,6 +342,7 @@ static int altr_i2c_xfer_msg(struct altr_i2c_dev *idev, struct i2c_msg *msg)
>   		altr_i2c_int_enable(idev, imask, true);
>   		altr_i2c_fill_tx_fifo(idev);
>   	}
> +	mutex_unlock(&idev->mutex);
>   
>   	time_left = wait_for_completion_timeout(&idev->msg_complete,
>   						ALTR_I2C_XFER_TIMEOUT);
> @@ -410,6 +417,7 @@ static int altr_i2c_probe(struct platform_device *pdev)
>   	idev->dev = &pdev->dev;
>   	init_completion(&idev->msg_complete);
>   	spin_lock_init(&idev->lock);
> +	mutex_init(&idev->mutex);
>   
>   	val = device_property_read_u32(idev->dev, "fifo-size",
>   				       &idev->fifo_size);
>