Re: [PATCH 1/3] media: i2c: imx219: Fix power sequence

[Lad, Prabhakar]

Hi Dave,

Thank you for the review.

On Mon, Mar 2, 2020 at 3:24 PM Dave Stevenson
<dave.stevenson@xxxxxxxxxxxxxxx> wrote:
>
> Hi Lad.
>
> Thanks again for the patch.
>
> On Fri, 28 Feb 2020 at 16:55, Lad Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> >
> > When supporting Rpi Camera v2 Module on the RZ/G2E, found the driver had
> > some issues with rcar mipi-csi driver. The sesnosr never entered into LP-11
>
> s/sesnosr/sensor
>
my bad shall fix that.

> > state.
> >
> > The powerup sequence in the datasheet[1] shows the sensor entering into
> > LP-11 in streaming mode, so to fix this issue transitions are performed
> > from "standby -> streaming -> standby" in the probe().
> >
> > With this commit the sensor is able to enter LP-11 mode during power up,
> > as expected by some CSI-2 controllers.
>
> I guess I'm lucky that the CSI2 receiver I deal with doesn't care on this front.
> The datasheet does seem to imply that the line is left in what appears
> to be LP-00 after power up, but this feels like a huge amount of stuff
> to do.
>
> > [1] https://publiclab.org/system/images/photos/000/023/294/original/
> > RASPBERRY_PI_CAMERA_V2_DATASHEET_IMX219PQH5_7.0.0_Datasheet_XXX.PDF
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > ---
> >  drivers/media/i2c/imx219.c | 33 +++++++++++++++++++++++++++++++++
> >  1 file changed, 33 insertions(+)
> >
> > diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
> > index f1effb5a5f66..8b48e148f2d0 100644
> > --- a/drivers/media/i2c/imx219.c
> > +++ b/drivers/media/i2c/imx219.c
> > @@ -1171,6 +1171,7 @@ static int imx219_check_hwcfg(struct device *dev)
> >
> >  static int imx219_probe(struct i2c_client *client)
> >  {
> > +       const struct imx219_reg_list *reg_list;
> >         struct device *dev = &client->dev;
> >         struct imx219 *imx219;
> >         int ret;
> > @@ -1224,6 +1225,38 @@ static int imx219_probe(struct i2c_client *client)
> >         /* Set default mode to max resolution */
> >         imx219->mode = &supported_modes[0];
> >
> > +       /* sensor doesn't enter to LP-11 state upon power up until and unless
>
> Remove "to"
>
will do.

> > +        * streaming is started, so upon power up set the default format and
> > +        * switch the modes: standby -> streaming -> standby
> > +        */
> > +       /* getting sensor out of sleep */
> > +       ret = imx219_write_reg(imx219, IMX219_REG_MODE_SELECT,
> > +                              IMX219_REG_VALUE_08BIT, IMX219_MODE_STANDBY);
>
> The datasheet says the default for IMX219_REG_MODE_SELECT is already 0
> / STANDY, so this should be unnecessary as we've only just powered up.
>
Agreed.

> > +       if (ret < 0)
> > +               goto error_power_off;
> > +       usleep_range(100, 110);
> > +
> > +       reg_list = &imx219->mode->reg_list;
> > +       ret = imx219_write_regs(imx219, reg_list->regs, reg_list->num_of_regs);
> > +       if (ret) {
> > +               dev_err(&client->dev, "%s failed to default mode\n", __func__);
> > +               goto error_power_off;
> > +       }
>
> Seeing as we don't want the images produced, and we're about to power
> the sensor back down again, do the default register settings do enough
> to allow the shift to LP-11? ie can we drop writing any mode setup
> registers here, and just got to STREAMING and back to STANDBY?
>
Yes shall replace the sequence.

> > +       /* getting sensor out of sleep */
>
> We already did that above. This is standby->streaming.
>
agreed.

> > +       ret = imx219_write_reg(imx219, IMX219_REG_MODE_SELECT,
> > +                              IMX219_REG_VALUE_08BIT, IMX219_MODE_STREAMING);
> > +       if (ret < 0)
> > +               goto error_power_off;
> > +       usleep_range(100, 110);
> > +
> > +       /* put sensor back to standby mode */
> > +       ret = imx219_write_reg(imx219, IMX219_REG_MODE_SELECT,
> > +                              IMX219_REG_VALUE_08BIT, IMX219_MODE_STANDBY);
> > +       if (ret < 0)
> > +               goto error_power_off;
> > +       usleep_range(100, 110);
> > +
Just the above two write_reg's should do the trick.

Cheers,
--Prabhakar

> >         ret = imx219_init_controls(imx219);
> >         if (ret)
> >                 goto error_power_off;
> > --
> > 2.20.1
>
> Cheers,
>   Dave