Re: [PATCH V1 6/6] i2c: tegra: remove BUG, BUG_ON

From: Bitan Biswas
Date: Fri Jun 07 2019 - 15:00:22 EST




On 6/7/19 5:18 AM, Dmitry Osipenko wrote:
07.06.2019 15:12, Dmitry Osipenko ÐÐÑÐÑ:
07.06.2019 15:08, Dmitry Osipenko ÐÐÑÐÑ:
07.06.2019 14:55, Bitan Biswas ÐÐÑÐÑ:
Remove redundant BUG_ON calls or replace with WARN_ON_ONCE
as needed. Replace BUG() with error handling code.
Define I2C_ERR_UNEXPECTED_STATUS for error handling.

Signed-off-by: Bitan Biswas <bbiswas@xxxxxxxxxx>
---
drivers/i2c/busses/i2c-tegra.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 4dfb4c1..c407bd7 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_UNEXPECTED_STATUS BIT(3)
#define PACKET_HEADER0_HEADER_SIZE_SHIFT 28
#define PACKET_HEADER0_PACKET_ID_SHIFT 16
@@ -515,7 +516,6 @@ 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);
val = i2c_readl(i2c_dev, I2C_RX_FIFO);
val = cpu_to_le32(val);
memcpy(buf, &val, buf_remaining);
@@ -523,7 +523,6 @@ 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);
i2c_dev->msg_buf_remaining = buf_remaining;
i2c_dev->msg_buf = buf;
@@ -581,7 +580,6 @@ 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);
memcpy(&val, buf, buf_remaining);
val = le32_to_cpu(val);
@@ -847,10 +845,13 @@ 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)
+ if (i2c_dev->msg_buf_remaining) {
tegra_i2c_empty_rx_fifo(i2c_dev);
- else
- BUG();
+ } else {
+ dev_err(i2c_dev->dev, "unexpected rx data request\n");
+ i2c_dev->msg_err |= I2C_ERR_UNEXPECTED_STATUS;
+ goto err;
+ }
}
if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
@@ -876,7 +877,7 @@ 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);
+ WARN_ON_ONCE(i2c_dev->msg_buf_remaining);
complete(&i2c_dev->msg_complete);
}
goto done;


Very nice, thank you very much! BTW, I think it may worth to add another
patch that will reset hardware state in a case of the warning since we
know that something gone wrong.

Reviewed-by: Dmitry Osipenko <digetx@xxxxxxxxx>


Something like that:

complete(&i2c_dev->msg_complete);

if (WARN_ON_ONCE(i2c_dev->msg_buf_remaining))
goto err;


Ah, that's inside the ISR, so maybe will make sense to just not complete
the transfer and let it timeout:

if (!WARN_ON_ONCE(i2c_dev->msg_buf_remaining))
complete(&i2c_dev->msg_complete);
OK. I shall send the updated patch.

-Thanks,
Bitan