Re: [PATCH v1] i2c: designware: Disable TX_EMPTY irq while waiting for block length byte

[Tam Chi Nguyen]

On 10/3/2023 15:11, Yann Sionneau wrote:
> Hi Tam,
>
> On 9/29/23 05:53, Tam Nguyen wrote:
> > During SMBus block data read process, we have seen high interrupt rate
> > because of TX_EMPTY irq status while waiting for block length byte (the
> > first data byte after the address phase). The interrupt handler does not
> > do anything because the internal state is kept as 
> > STATUS_WRITE_IN_PROGRESS.
> > Hence, we should disable TX_EMPTY irq until I2C DW receives first data
> > byte from I2C device, then re-enable it.
> >
> > It takes 0.789 ms for host to receive data length from slave.
> > Without the patch, i2c_dw_isr is called 99 times by TX_EMPTY interrupt.
> > And it is none after applying the patch.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Chuong Tran <chuong@xxxxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Tam Nguyen <tamnguyenchi@xxxxxxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/i2c/busses/i2c-designware-master.c | 13 +++++++++++++
> >   1 file changed, 13 insertions(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-designware-master.c 
> > b/drivers/i2c/busses/i2c-designware-master.c
> > index 55ea91a63382..2152b1f9b27c 100644
> > --- a/drivers/i2c/busses/i2c-designware-master.c
> > +++ b/drivers/i2c/busses/i2c-designware-master.c
> > @@ -462,6 +462,13 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
> >           if (buf_len > 0 || flags & I2C_M_RECV_LEN) {
> >               /* more bytes to be written */
> >               dev->status |= STATUS_WRITE_IN_PROGRESS;
> > +            /*
> > +             * In I2C_FUNC_SMBUS_BLOCK_DATA case, there is no data
> > +             * to send before receiving data length from slave.
> > +             * Disable TX_EMPTY while waiting for data length byte
> > +             */
> > +            if (flags & I2C_M_RECV_LEN)
> > +                intr_mask &= ~DW_IC_INTR_TX_EMPTY;
> >               break;
> >           } else
> >               dev->status &= ~STATUS_WRITE_IN_PROGRESS;
> > @@ -485,6 +492,7 @@ i2c_dw_recv_len(struct dw_i2c_dev *dev, u8 len)
> >   {
> >       struct i2c_msg *msgs = dev->msgs;
> >       u32 flags = msgs[dev->msg_read_idx].flags;
> > +    u32 intr_mask;
> >         /*
> >        * Adjust the buffer length and mask the flag
> > @@ -495,6 +503,11 @@ i2c_dw_recv_len(struct dw_i2c_dev *dev, u8 len)
> >       msgs[dev->msg_read_idx].len = len;
> >       msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN;
> >   +    /* Re-enable TX_EMPTY interrupt. */
> > +    regmap_read(dev->map, DW_IC_INTR_MASK, &intr_mask);
> > +    intr_mask |= DW_IC_INTR_TX_EMPTY;
> > +    regmap_write(dev->map, DW_IC_INTR_MASK, intr_mask);
> > +
> >       return len;
> >   }
>
> I tested this patch on Kalray k200 and k200lp boards (Coolidge SoC, 
> kvx arch). With this patch all our CI pipelines are green.
Thank you for your time to test this patch.

> Tested-by: Yann Sionneau <ysionneau@xxxxxxxxxxxxx>