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

[Bitan Biswas]

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