Re: [Patch v2 1/3] media: ov5640: add PIXEL_RATE control

Sakari Ailus
2019-10-03T14:32:51Z

Hi Benoit,

On Thu, Oct 03, 2019 at 07:07:41AM -0500, Benoit Parrot wrote:
> Sakari Ailus <sakari.ailus@linux.intel.com> wrote on Thu [2019-Oct-03 10:22:51 +0300]:
> > Hi Jacopo, Benoit,
> >
> > On Thu, Oct 03, 2019 at 09:17:14AM +0200, Jacopo Mondi wrote:
> > > Hi Benoit,
> > >
> > > On Wed, Oct 02, 2019 at 08:51:32AM -0500, Benoit Parrot wrote:
> > > > Add v4l2 controls to report the pixel rates of each mode. This is
> > > > needed by some CSI2 receiver in order to perform proper DPHY
> > > > configuration.
> > > >
> > > > Signed-off-by: Benoit Parrot <bparrot@ti.com>
> > > > ---
> > > > drivers/media/i2c/ov5640.c | 25 +++++++++++++++++++++++++
> > > > 1 file changed, 25 insertions(+)
> > > >
> > > > diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
> > > > index 500d9bbff10b..5198dc887400 100644
> > > > --- a/drivers/media/i2c/ov5640.c
> > > > +++ b/drivers/media/i2c/ov5640.c
> > > > @@ -193,6 +193,9 @@ struct ov5640_mode_info {
> > > >
> > > > struct ov5640_ctrls {
> > > > struct v4l2_ctrl_handler handler;
> > > > + struct {
> > > > + struct v4l2_ctrl *pixel_rate;
> > > > + };
> > >
> > > Do you need to wrap this v4l2_ctrl in it's own unnamed struct? Other
> > > controls here declared in this way are clustered and, if I'm not
> > > mistaken, using unnamed struct to wrap them is just a typographically
> > > nice way to convey that. I think your new control could be declared
> > > without a wrapping struct { }.
> > >
> > > > struct {
> > > > struct v4l2_ctrl *auto_exp;
> > > > struct v4l2_ctrl *exposure;
> > > > @@ -2194,6 +2197,16 @@ static int ov5640_try_fmt_internal(struct v4l2_subdev *sd,
> > > > return 0;
> > > > }
> > > >
> > > > +static u64 ov5640_calc_pixel_rate(struct ov5640_dev *sensor)
> > > > +{
> > > > + u64 rate;
> > > > +
> > > > + rate = sensor->current_mode->vtot * sensor->current_mode->htot;
> > > > + rate *= ov5640_framerates[sensor->current_fr];
> > > > +
> > > > + return rate;
> > > > +}
> > > > +
> > >
> > > Just to point out this is the -theoretical- pixel rate, and might be
> > > quite different from the one calculated by the clock tree tuning
> > > procedure (which should be updated to match Hugues' latest findings).
> >
> > Hmm. Considering the xclk rate may be pretty much anything, I'd suppose
> > the value above would only be correct for a given xclk rate.
>
> I am not sure about that, different xclk rate might yield slightly
> different byte clock, but all in all the resolution and framerate pretty
> much dictate the end result, no?

Interestingly, the driver determines the PLL configuration based on the
pixels per line and lines per frame (including blanking) and the frames per
seconds. I guess it's always been like that in this driver.

So I agree the target frame rate can be used for this.

You could change ov5640_set_mode() to use this function as well to avoid
doing the same calculation twice in different places in the driver. Up to
you.

>
> >
> > Could this be simply calculated from the clock tree configuration, to get
> > the right value in all cases?
>
> It probably could, and as I said earlier I gave it a try and failed, since
> the theoretical value worked for me that's what I went with. Those are the
> same values that Maxime's patch referred to. (dfbfb7aa832cdb media: ov5640:
> Compute the clock rate at runtime).
>
> Here I am just "publishing it".
>
> Benoit
>
> >
> > >
> > > > static int ov5640_set_fmt(struct v4l2_subdev *sd,
> > > > struct v4l2_subdev_pad_config *cfg,
> > > > struct v4l2_subdev_format *format)
> > > > @@ -2233,6 +2246,8 @@ static int ov5640_set_fmt(struct v4l2_subdev *sd,
> > > > if (mbus_fmt->code != sensor->fmt.code)
> > > > sensor->pending_fmt_change = true;
> > > >
> > > > + __v4l2_ctrl_s_ctrl_int64(sensor->ctrls.pixel_rate,
> > > > + ov5640_calc_pixel_rate(sensor));
> > > > out:
> > > > mutex_unlock(&sensor->lock);
> > > > return ret;
> > > > @@ -2657,6 +2672,13 @@ static int ov5640_init_controls(struct ov5640_dev *sensor)
> > > > /* we can use our own mutex for the ctrl lock */
> > > > hdl->lock = &sensor->lock;
> > > >
> > > > + /* Clock related controls */
> > > > + ctrls->pixel_rate =
> > > > + v4l2_ctrl_new_std(hdl, ops,
> > >
> > > If you like it better, this could fit in 1 line
> > >
> > > ctrls->pixel_rate = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_PIXEL_RATE,
> > > 0, INT_MAX, 1,
> > > ov5640_calc_pixel_rate(sensor)
> > >
> > > Thanks
> > > j
> > >
> > > > + V4L2_CID_PIXEL_RATE, 0, INT_MAX, 1,
> > > > + ov5640_calc_pixel_rate(sensor));
> > >
> > >
> > > > + ctrls->pixel_rate->flags |= V4L2_CTRL_FLAG_READ_ONLY;
> >
> > Note that ctrls->pixel_rate is NULL if e.g. memory allocation fails when
> > creating the control.
> >
> > > > +
> > > > /* Auto/manual white balance */
> > > > ctrls->auto_wb = v4l2_ctrl_new_std(hdl, ops,
> > > > V4L2_CID_AUTO_WHITE_BALANCE,
> > > > @@ -2816,6 +2838,9 @@ static int ov5640_s_frame_interval(struct v4l2_subdev *sd,
> > > > sensor->frame_interval = fi->interval;
> > > > sensor->current_mode = mode;
> > > > sensor->pending_mode_change = true;
> > > > +
> > > > + __v4l2_ctrl_s_ctrl_int64(sensor->ctrls.pixel_rate,
> > > > + ov5640_calc_pixel_rate(sensor));
> > > > }
> > > > out:
> > > > mutex_unlock(&sensor->lock);
> >
> > --
> > Regards,
> >
> > Sakari Ailus
> > sakari.ailus@linux.intel.com

--
Sakari Ailus
sakari.ailus@linux.intel.com