Re: [PATCH 3/3] media: i2c: max9286: Support manual framesync operation

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Hi Jacopo,

On Fri, Dec 17, 2021 at 06:05:02PM +0200, Laurent Pinchart wrote:
> On Fri, Dec 17, 2021 at 12:14:03PM +0100, Jacopo Mondi wrote:
> > On Fri, Dec 17, 2021 at 12:09:46AM +0200, Laurent Pinchart wrote:
> > > From: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > >
> > > The MAX9286 can generate a framesync signal to synchronize the cameras,
> > > using an internal timer. Support this mode of operation and configure it
> > > through the .s_frameinterval() operation. If the frame interval is not
> > > 0, framesync is switched to manual mode with the specified interval,
> > > otherwise automatic mode is used.
> > >
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > ---
> > >  drivers/media/i2c/max9286.c | 66 +++++++++++++++++++++++++++++++++++--
> > >  1 file changed, 63 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> > > index fa2f6a823fe6..dce1146635d2 100644
> > > --- a/drivers/media/i2c/max9286.c
> > > +++ b/drivers/media/i2c/max9286.c
> > > @@ -174,6 +174,7 @@ struct max9286_priv {
> > >  	struct v4l2_ctrl *pixelrate;
> > >
> > >  	struct v4l2_mbus_framefmt fmt[MAX9286_N_SINKS];
> > > +	struct v4l2_fract interval;
> > >
> > >  	/* Protects controls and fmt structures */
> > >  	struct mutex mutex;
> > > @@ -474,6 +475,37 @@ static int max9286_check_config_link(struct max9286_priv *priv,
> > >  	return 0;
> > >  }
> > >
> > > +static void max9286_set_fsync_period(struct max9286_priv *priv)
> > > +{
> > > +	u32 fsync;
> > > +
> > > +	if (!priv->interval.numerator || !priv->interval.denominator) {
> > > +		/*
> > > +		 * Special case, a null interval enables automatic FRAMESYNC
> > > +		 * mode. FRAMESYNC is taken from the slowest link.
> > > +		 */
> > > +		max9286_write(priv, 0x01, MAX9286_FSYNCMODE_INT_HIZ |
> > > +			      MAX9286_FSYNCMETH_AUTO);
> > > +		return;
> > > +	}
> > > +
> > > +	/*
> > > +	 * Manual FRAMESYNC
> > > +	 *
> > > +	 * The FRAMESYNC generator is configured with a period expressed as a
> > > +	 * number of PCLK periods, which runs at 75MHz.
> > > +	 */
> > > +	fsync = div_u64(75000000ULL * priv->interval.numerator,
> > > +			priv->interval.denominator);
> > 
> > Don't we calculate the pixel rate dynamically based on the number of
> > enabled sources ?
> 
> That's a good point, this hardcodes operation for 4 cameras. I'll see
> how I can fix that.
> 
> > > +
> > > +	max9286_write(priv, 0x01, MAX9286_FSYNCMODE_INT_OUT |
> > > +		      MAX9286_FSYNCMETH_MANUAL);
> > > +
> > > +	max9286_write(priv, 0x06, (fsync >> 0) & 0xff);
> > > +	max9286_write(priv, 0x07, (fsync >> 8) & 0xff);
> > > +	max9286_write(priv, 0x08, (fsync >> 16) & 0xff);
> > > +}
> > > +
> > >  /* -----------------------------------------------------------------------------
> > >   * V4L2 Subdev
> > >   */
> > > @@ -656,6 +688,8 @@ static int max9286_s_stream(struct v4l2_subdev *sd, int enable)
> > >  	int ret;
> > >
> > >  	if (enable) {
> > > +		max9286_set_fsync_period(priv);
> > > +
> > >  		/*
> > >  		 * The frame sync between cameras is transmitted across the
> > >  		 * reverse channel as GPIO. We must open all channels while
> > > @@ -715,6 +749,32 @@ static int max9286_s_stream(struct v4l2_subdev *sd, int enable)
> > >  	return 0;
> > >  }
> > >
> > > +static int max9286_g_frame_interval(struct v4l2_subdev *sd,
> > > +				    struct v4l2_subdev_frame_interval *interval)
> > > +{
> > > +	struct max9286_priv *priv = sd_to_max9286(sd);
> > > +
> > > +	if (interval->pad == MAX9286_SRC_PAD)
> > 
> > Ah!
> > 
> > I would have expected, as this setting applies to all cameras, and
> > consequentially to the output image stream frame rate, that the
> > operation should have been done on the single source pad... Why is
> > this not the case ?
> 
> I went back and forth between the two, I think it would work fine on the
> source pad as well. I'll give it a try.

Note that once we'll move to the muxed streams API, the frame interval
will be per stream, so setting it on the source pad won't make much of a
difference. What do you think ?

> > > +		return -EINVAL;
> > > +
> > > +	interval->interval = priv->interval;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int max9286_s_frame_interval(struct v4l2_subdev *sd,
> > > +				    struct v4l2_subdev_frame_interval *interval)
> > > +{
> > > +	struct max9286_priv *priv = sd_to_max9286(sd);
> > > +
> > > +	if (interval->pad == MAX9286_SRC_PAD)
> > > +		return -EINVAL;
> > > +
> > > +	priv->interval = interval->interval;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >  static int max9286_enum_mbus_code(struct v4l2_subdev *sd,
> > >  				  struct v4l2_subdev_state *sd_state,
> > >  				  struct v4l2_subdev_mbus_code_enum *code)
> > > @@ -806,6 +866,8 @@ static int max9286_get_fmt(struct v4l2_subdev *sd,
> > >
> > >  static const struct v4l2_subdev_video_ops max9286_video_ops = {
> > >  	.s_stream	= max9286_s_stream,
> > > +	.g_frame_interval = max9286_g_frame_interval,
> > > +	.s_frame_interval = max9286_s_frame_interval,
> > >  };
> > >
> > >  static const struct v4l2_subdev_pad_ops max9286_pad_ops = {
> > > @@ -998,9 +1060,7 @@ static int max9286_setup(struct max9286_priv *priv)
> > >  		      MAX9286_CSILANECNT(priv->csi2_data_lanes) |
> > >  		      MAX9286_DATATYPE_YUV422_8BIT);
> > >
> > > -	/* Automatic: FRAMESYNC taken from the slowest Link. */
> > > -	max9286_write(priv, 0x01, MAX9286_FSYNCMODE_INT_HIZ |
> > > -		      MAX9286_FSYNCMETH_AUTO);
> > > +	max9286_set_fsync_period(priv);
> > >
> > >  	/* Enable HS/VS encoding, use D14/15 for HS/VS, invert VS. */
> > >  	max9286_write(priv, 0x0c, MAX9286_HVEN | MAX9286_INVVS |

-- 
Regards,

Laurent Pinchart



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