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

[Bitan Biswas <bbiswas@xxxxxxxxxx>]

On 6/7/19 11:55 AM, Bitan Biswas wrote:
> On 6/7/19 5:18 AM, Dmitry Osipenko wrote:
> > 07.06.2019 15:12, Dmitry Osipenko пишет:
> > > 07.06.2019 15:08, Dmitry Osipenko пишет:
> > > > 07.06.2019 14:55, Bitan Biswas пишет:
> > > > > 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.
I see that there is already err label in the ISR that could be jumped 
into. Hence, planning to share updated patch with the error handling.

-regards,
 Bitan