On 6/18/19 4:09 AM, Bitan Biswas wrote:
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;
Please get back if there are any further comments regarding this patch.
-regards,
Bitan
