Re: [PATCH 6/7] iio: imu: st_lsm6dsx: add hw FIFO support to i2c controller

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 4 Nov 2018 19:14:22 +0100
Lorenzo Bianconi <lorenzo.bianconi@redhat.com> wrote:

> >
> > On Sun,  4 Nov 2018 15:39:05 +0100
> > Lorenzo Bianconi <lorenzo.bianconi@redhat.com> wrote:
> >  
> > > Introduce hw FIFO support to lsm6dsx sensorhub. Current implementation
> > > use SLV0 for slave configuration and SLV{1,2,3} to read data and
> > > push them into the hw FIFO  
> > So, the words 'Current Implementation' suggest you are already thinking
> > of other implementations?  Perhaps a note here on why you chose this
> > method, it's limitations etc and why you might want to change it in future?
> > (I'm guessing when you potentially have 4 slave devices...)  
> 
> ack, will do in v2
> 
Great.  
> > > +static int
> > > +st_lsm6dsx_push_tagged_data(struct st_lsm6dsx_hw *hw, u8 tag,
> > > +                         u8 *data, s64 ts)
> > > +{
> > > +     struct st_lsm6dsx_sensor *sensor;
> > > +     struct iio_dev *iio_dev;
> > > +
> > > +     switch (tag) {
> > > +     case ST_LSM6DSX_GYRO_TAG:
> > > +             iio_dev = hw->iio_devs[ST_LSM6DSX_ID_GYRO];
> > > +             sensor = iio_priv(iio_dev);
> > > +             break;
> > > +     case ST_LSM6DSX_ACC_TAG:
> > > +             iio_dev = hw->iio_devs[ST_LSM6DSX_ID_ACC];
> > > +             sensor = iio_priv(iio_dev);
> > > +             break;
> > > +     case ST_LSM6DSX_EXT0_TAG:
> > > +             if (hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT0))
> > > +                     iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT0];
> > > +             else if (hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT1))
> > > +                     iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT1];
> > > +             else
> > > +                     iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT2];  
> >
> > I would suggest this is non obvious enough to deserve some comments.
> > I 'think' EXT0_TAG gets used for the first enabled additional channel?  
> 
> EXT0_TAG will be used for the first enabled sensor, so if we enable
> channel 2 and 3 (SLV2 and SLV3; first 'data' channel is 1 since 0 is
> used just for configuration), we will receive data with TAG0 and TAG1
> There is no relation between tags used and i2c slave channels IIRC

Great, add that comment to v2.

> 
> >
> >  
> > > +             sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_ACC]);  
> > Perhaps a comment that explains this is just to get the right timestamp
> > or maybe better just have ts_ref as the local variable then it's
> > more obvious.
> >  
> > > +             break;
> > > +     case ST_LSM6DSX_EXT1_TAG:
> > > +             if (hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT1))
> > > +                     iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT1];  
> > Under my assumption above about first come first served if 1 and 2
> > are enabled but not 0, I think you will get the iio_dev for 1 for
> > both of them...
I 'think' my query still holds here..
> >  
> > > +             else
> > > +                     iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT2];
> > > +             sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_ACC]);
> > > +             break;
...
> > > @@ -574,13 +612,19 @@ static int st_lsm6dsx_update_fifo(struct iio_dev *iio_dev, bool enable)
> > >                       goto out;
> > >       }
> > >
> > > -     err = st_lsm6dsx_sensor_set_enable(sensor, enable);
> > > -     if (err < 0)
> > > -             goto out;
> > > +     if (sensor->id == ST_LSM6DSX_ID_EXT0 ||
> > > +         sensor->id == ST_LSM6DSX_ID_EXT1 ||
> > > +         sensor->id == ST_LSM6DSX_ID_EXT2) {
> > > +             st_lsm6dsx_shub_set_enable(sensor, enable);  
> > Rather feels like this should ultimately be able to fail and should
> > have error handling?  
> 
> correct :) I will fix in v2
> 
> >  
> > > +     } else {
> > > +             err = st_lsm6dsx_sensor_set_enable(sensor, enable);
> > > +             if (err < 0)
> > > +                     goto out;
...
> > > +out:
> > > +     mutex_unlock(&hw->page_lock);
> > > +
> > > +     return err;
> > > +}
> > > +
> > >  static int st_lsm6dsx_shub_master_enable(struct st_lsm6dsx_sensor *sensor,
> > >                                        bool enable)
> > >  {
> > > @@ -238,8 +258,21 @@ st_lsm6dsx_shub_write(struct st_lsm6dsx_sensor *sensor, u8 addr,
> > >       int err, i;
> > >
> > >       hub_settings = &hw->settings->shub_settings;
> > > +     if (hub_settings->wr_once.addr) {
> > > +             unsigned int data;
> > > +
> > > +             data = ST_LSM6DSX_SHIFT_VAL(1, hub_settings->wr_once.mask);
> > > +             err = st_lsm6dsx_shub_write_reg_with_mask(hw,
> > > +                     hub_settings->wr_once.addr,
> > > +                     hub_settings->wr_once.mask,
> > > +                     data);
> > > +             if (err < 0)
> > > +                     return err;
> > > +     }
> > > +
> > >       slv_addr = ST_LSM6DSX_SLV_ADDR(0, hub_settings->slv0_addr);
> > >       config[0] = sensor->ext_info.addr << 1;
> > > +  
> > Ahah! caught you in an unrelated white space change ;)  Meh. In a series this
> > big there was sure to be one somewhere and it doesn't really matter that much.  
> 
> :) will fix it in v2
> Thx a lot for the fast review
You are welcome.  A rare thing from me, but I just happened to be catching up
today.

> 
> Regards,
> Lorenzo
>