[PATCH v2] i2c: tegra: Check for overflow errors with BUG_ON.

[Rhyland Klein]

On Mon, 2011-08-15 at 18:32 -0700, Doug Anderson wrote:
> This change doesn't fix any known problems but turns
> on the overflow detection feature of the i2c controller
> in the hopes of flushing out any current (or future)
> bugs in the i2c driver.
> 
> Inspired by a change on nvidia's git server:
>   http://nv-tegra.nvidia.com/gitweb/?p=linux-2.6.git;a=commit;h=266d1b7397284505e55d06254b497cb32be07b69
> 
> Signed-off-by: Doug Anderson <dianders at chromium.org>
> ---
> This takes Felipe Balbi's suggestion of making the overflow
> error non-fatal.
> 
>  drivers/i2c/busses/i2c-tegra.c |   17 ++++++++++++++---
>  1 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 2440b74..34634b7 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -83,6 +83,7 @@
>  #define I2C_ERR_NO_ACK				0x01
>  #define I2C_ERR_ARBITRATION_LOST		0x02
>  #define I2C_ERR_UNKNOWN_INTERRUPT		0x04
> +#define I2C_ERR_FIFO_OVERFLOW			0x08
>  
>  #define PACKET_HEADER0_HEADER_SIZE_SHIFT	28
>  #define PACKET_HEADER0_PACKET_ID_SHIFT		16
> @@ -367,7 +368,8 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>  static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
>  {
>  	u32 status;
> -	const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
> +	const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
> +		I2C_INT_TX_FIFO_OVERFLOW;
>  	struct tegra_i2c_dev *i2c_dev = dev_id;
>  
>  	status = i2c_readl(i2c_dev, I2C_INT_STATUS);
> @@ -389,6 +391,14 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
>  	}
>  
>  	if (unlikely(status & status_err)) {
> +		/*
> +		 * Overflow should be impossible unless we've got a
> +		 * bug in the driver, but check anyway.
> +		 */
> +		if (status & I2C_INT_TX_FIFO_OVERFLOW) {
> +			WARN_ON(1);
> +			i2c_dev->msg_err |= I2C_ERR_FIFO_OVERFLOW;
> +		}
>  		if (status & I2C_INT_NO_ACK)
>  			i2c_dev->msg_err |= I2C_ERR_NO_ACK;
>  		if (status & I2C_INT_ARBITRATION_LOST)
> @@ -423,7 +433,7 @@ err:
>  	/* An error occurred, mask all interrupts */
>  	tegra_i2c_mask_irq(i2c_dev, I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
>  		I2C_INT_PACKET_XFER_COMPLETE | I2C_INT_TX_FIFO_DATA_REQ |
> -		I2C_INT_RX_FIFO_DATA_REQ);
> +		I2C_INT_RX_FIFO_DATA_REQ | I2C_INT_TX_FIFO_OVERFLOW);
>  	i2c_writel(i2c_dev, status, I2C_INT_STATUS);
>  	if (i2c_dev->is_dvc)
>  		dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
> @@ -473,7 +483,8 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
>  	if (!(msg->flags & I2C_M_RD))
>  		tegra_i2c_fill_tx_fifo(i2c_dev);
>  
> -	int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
> +	int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
> +		I2C_INT_TX_FIFO_OVERFLOW;
>  	if (msg->flags & I2C_M_RD)
>  		int_mask |= I2C_INT_RX_FIFO_DATA_REQ;
>  	else if (i2c_dev->msg_buf_remaining)

Seems good to me.

Acked-by: Rhyland Klein <rklein at nvidia.com>