The usage of BUG() macro is generally discouraged in kernel, unless it's a problem that results in a physical damage or loss of data. This patch removes unnecessary BUG() macros and replaces the rest with warning. Signed-off-by: Bitan Biswas <bbiswas@xxxxxxxxxx> --- drivers/i2c/busses/i2c-tegra.c | 47 +++++++++++++++++++++++++++++++++++------- 1 file changed, 39 insertions(+), 8 deletions(-) diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index 4dfb4c1..e9ff96d 100644 --- a/drivers/i2c/busses/i2c-tegra.c +++ b/drivers/i2c/busses/i2c-tegra.c @@ -73,6 +73,7 @@ #define I2C_ERR_NO_ACK BIT(0) #define I2C_ERR_ARBITRATION_LOST BIT(1) #define I2C_ERR_UNKNOWN_INTERRUPT BIT(2) +#define I2C_ERR_RX_BUFFER_OVERFLOW BIT(3) #define PACKET_HEADER0_HEADER_SIZE_SHIFT 28 #define PACKET_HEADER0_PACKET_ID_SHIFT 16 @@ -489,6 +490,13 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev) size_t buf_remaining = i2c_dev->msg_buf_remaining; int words_to_transfer; + /* + * Catch overflow due to message fully sent + * before the check for RX FIFO availability. + */ + if (WARN_ON_ONCE(!(i2c_dev->msg_buf_remaining))) + return -EINVAL; + if (i2c_dev->hw->has_mst_fifo) { val = i2c_readl(i2c_dev, I2C_MST_FIFO_STATUS); rx_fifo_avail = (val & I2C_MST_FIFO_STATUS_RX_MASK) >> @@ -515,7 +523,11 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev) * prevent overwriting past the end of buf */ if (rx_fifo_avail > 0 && buf_remaining > 0) { - BUG_ON(buf_remaining > 3); + /* + * buf_remaining > 3 check not needed as rx_fifo_avail == 0 + * when (words_to_transfer was > rx_fifo_avail) earlier + * in this function. + */ val = i2c_readl(i2c_dev, I2C_RX_FIFO); val = cpu_to_le32(val); memcpy(buf, &val, buf_remaining); @@ -523,7 +535,10 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev) rx_fifo_avail--; } - BUG_ON(rx_fifo_avail > 0 && buf_remaining > 0); + /* RX FIFO must be drained, otherwise it's an Overflow case. */ + if (WARN_ON_ONCE(rx_fifo_avail)) + return -EINVAL; + i2c_dev->msg_buf_remaining = buf_remaining; i2c_dev->msg_buf = buf; @@ -581,7 +596,11 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev) * boundary and fault. */ if (tx_fifo_avail > 0 && buf_remaining > 0) { - BUG_ON(buf_remaining > 3); + /* + * buf_remaining > 3 check not needed as tx_fifo_avail == 0 + * when (words_to_transfer was > tx_fifo_avail) earlier + * in this function for non-zero words_to_transfer. + */ memcpy(&val, buf, buf_remaining); val = le32_to_cpu(val); @@ -847,10 +866,15 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) if (!i2c_dev->is_curr_dma_xfer) { if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) { - if (i2c_dev->msg_buf_remaining) - tegra_i2c_empty_rx_fifo(i2c_dev); - else - BUG(); + if (tegra_i2c_empty_rx_fifo(i2c_dev)) { + /* + * Overflow error condition: message fully sent, + * with no XFER_COMPLETE interrupt but hardware + * asks to transfer more. + */ + i2c_dev->msg_err |= I2C_ERR_RX_BUFFER_OVERFLOW; + goto err; + } } if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) { @@ -876,7 +900,14 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) if (status & I2C_INT_PACKET_XFER_COMPLETE) { if (i2c_dev->is_curr_dma_xfer) i2c_dev->msg_buf_remaining = 0; - BUG_ON(i2c_dev->msg_buf_remaining); + /* + * Underflow error condition: XFER_COMPLETE before message + * fully sent. + */ + if (WARN_ON_ONCE(i2c_dev->msg_buf_remaining)) { + i2c_dev->msg_err |= I2C_ERR_UNKNOWN_INTERRUPT; + goto err; + } complete(&i2c_dev->msg_complete); } goto done; -- 2.7.4