RE: [PATCH RESEND] i2c: tegra: Add SMBus block read function

[Akhil R]

> 10.02.2022 18:36, Akhil R пишет:
> > Emulate SMBus block read using ContinueXfer to read the length byte
> >
> > Signed-off-by: Akhil R <akhilrajeev@xxxxxxxxxx>
> > ---
> >  drivers/i2c/busses/i2c-tegra.c | 18 ++++++++++++++++--
> >  1 file changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> > index 03cea102ab76..2941e42aa6a0 100644
> > --- a/drivers/i2c/busses/i2c-tegra.c
> > +++ b/drivers/i2c/busses/i2c-tegra.c
> > @@ -1233,6 +1233,11 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev
> *i2c_dev,
> >               return err;
> >
> >       i2c_dev->msg_buf = msg->buf;
> > +
> > +     /* The condition true implies smbus block read and len is already read */
> > +     if (msg->flags & I2C_M_RECV_LEN && end_state !=
> MSG_END_CONTINUE)
> > +             i2c_dev->msg_buf = msg->buf + 1;
> > +
> >       i2c_dev->msg_buf_remaining = msg->len;
> >       i2c_dev->msg_err = I2C_ERR_NONE;
> >       i2c_dev->msg_read = !!(msg->flags & I2C_M_RD);
> > @@ -1389,6 +1394,15 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap,
> struct i2c_msg msgs[],
> >                       else
> >                               end_type = MSG_END_REPEAT_START;
> >               }
> > +             /* If M_RECV_LEN use ContinueXfer to read the first byte */
> > +             if (msgs[i].flags & I2C_M_RECV_LEN) {
> > +                     ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i],
> MSG_END_CONTINUE);
> > +                     if (ret)
> > +                             break;
> > +                     /* Set the read byte as msg len */
> > +                     msgs[i].len = msgs[i].buf[0];
> > +                     dev_dbg(i2c_dev->dev, "reading %d bytes\n", msgs[i].len);
> > +             }
> >               ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], end_type);
> >               if (ret)
> >                       break;
> > @@ -1416,10 +1430,10 @@ static u32 tegra_i2c_func(struct i2c_adapter
> *adap)
> >  {
> >       struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
> >       u32 ret = I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL &
> ~I2C_FUNC_SMBUS_QUICK) |
> > -               I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
> > +               I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
> >
> >       if (i2c_dev->hw->has_continue_xfer_support)
> > -             ret |= I2C_FUNC_NOSTART;
> > +             ret |= I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_READ_BLOCK_DATA;
> >
> >       return ret;
> >  }
> 
> Please describe how this was tested.
This is tested using an I2C EEPROM to emulate SMBus block read in which
we read the first byte as the length of bytes to read. This is an expected
feature for NVIDIA Grace chipset where there will be an actual SMBus device.

Thanks,
Akhil