Re: [PATCH v1] i2c: designware: Handle invalid SMBus block data response length

[Tam Chi Nguyen]

Hi Jarkko

On 5/24/2023 19:33, Jarkko Nikula wrote:
> Hi
>
> On 5/23/23 11:21, Tam Nguyen wrote:
> > In I2C_FUNC_SMBUS_BLOCK_DATA case, the I2C Designware driver does not
> > handle correctly when it receives the length of SMBus block data
> > response from SMBus slave device, which is outside the range 1-32 bytes.
> > Consequently, the I2C Designware bus is stuck and cannot recover.
> > Because if IC_EMPTYFIFO_HOLD_MASTER_EN is set, which cannot be detected
> > from the registers, the controller can be disabled if the STOP bit is 
> > set.
> > But it is only set after receiving block data response length.
> >
> > Hence, to prevent the bus from stuck condition, after receiving the
> > invalid block data response length, the driver will read another byte
> > with STOP bit set.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Tam Nguyen <tamnguyenchi@xxxxxxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/i2c/busses/i2c-designware-master.c | 15 +++++++++++++--
> >   1 file changed, 13 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-designware-master.c 
> > b/drivers/i2c/busses/i2c-designware-master.c
> > index 55ea91a63382..94dadd785ed0 100644
> > --- a/drivers/i2c/busses/i2c-designware-master.c
> > +++ b/drivers/i2c/busses/i2c-designware-master.c
> > @@ -527,8 +527,19 @@ i2c_dw_read(struct dw_i2c_dev *dev)
> >                 regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
> >               /* Ensure length byte is a valid value */
> > -            if (flags & I2C_M_RECV_LEN &&
> > -                (tmp & DW_IC_DATA_CMD_DAT) <= I2C_SMBUS_BLOCK_MAX && 
> > tmp > 0) {
> > +            if (flags & I2C_M_RECV_LEN) {
> > +                /*
> > +                 * if IC_EMPTYFIFO_HOLD_MASTER_EN is set, which 
> > cannot be
> > +                 * detected from the registers, the controller can be
> > +                 * disabled if the STOP bit is set. But it is only set
> > +                 * after receiving block data response length in
> > +                 * I2C_FUNC_SMBUS_BLOCK_DATA case. That needs to read
> > +                 * another byte with STOP bit set when the block data
> > +                 * response length is invalid to complete the 
> > transaction.
> > +                 */
> > +                if ((tmp & DW_IC_DATA_CMD_DAT) > I2C_SMBUS_BLOCK_MAX 
> > || tmp == 0)
> > +                    tmp = 1;
> > +
> >                   len = i2c_dw_recv_len(dev, tmp);
> >               }
> >               *buf++ = tmp;
>
> Looks otherwise good to me but I'm wondering the "tmp == 0" test can 
> it have the bit 11 set (on a HW where it's supported) and should it be 
> covered with DW_IC_DATA_CMD_DAT mask too? Please see commit 
> f53f15ba5a85 ("i2c: designware: Get right data length").

You're right. We should use the DW_IC_DATA_CMD_DAT mask to get the data 
part if HW supports reading bit 11 from IC_DATA_CMD. I will update it in v2.

Best regards,
Tam Nguyen