Re: [PATCH] rcar-csi2: Allow configuring of video standard

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Niklas,

(CC'ing Sakari)

On Thu, Mar 07, 2019 at 01:38:20AM +0100, Niklas Söderlund wrote:
> On 2019-03-07 02:26:45 +0200, Laurent Pinchart wrote:
> > On Thu, Mar 07, 2019 at 01:22:36AM +0100, Niklas Söderlund wrote:
> >> On 2019-03-07 02:13:18 +0200, Laurent Pinchart wrote:
> >>> On Sat, Feb 16, 2019 at 11:57:58PM +0100, Niklas Söderlund wrote:
> >>>> Allow the hardware to to do proper field detection for interlaced field
> >>>> formats by implementing s_std() and g_std(). Depending on which video
> >>>> standard is selected the driver needs to setup the hardware to correctly
> >>>> identify fields.
> >>> 
> >>> I don't think this belongs to the CSI-2 receiver. Standards are really
> >>> an analog concept, and should be handled by the analog front-end. At the
> >>> CSI-2 level there's no concept of analog standard anymore.
> >> 
> >> I agree it should be handled by the analog front-end. This is patch just 
> >> lets the user propagate the information in the pipeline. The driver 
> >> could instead find its source subdevice in the media graph and ask which 
> >> standard it's supplying.
> >> 
> >> I wrestled a bit with this and went with this approach as it then works 
> >> the same as with other format information, such as dimensions and pixel 
> >> format. If the driver acquires the standard by itself why should it no 
> >> the same for the format? I'm willing to change this but I would like to 
> >> understand where the divider for format propagating in kernel and 
> >> user-space is :-)
> >> 
> >> Also what if there are subdevices between rcar-csi2 and the analog 
> >> front-end which do not support the g_std operation?
> > 
> > My point is that the analog standard shouldn't be propagated at all,
> > neither inside the kernel nor in userspace, as it is not applicable to
> > CSI-2.
> 
> This is not related to CSI-2 if I understand it. It is related to the 
> outputed field signal on the parallel output from CSI-2 facing the VINs.  
> See chapter "25.4.5 FLD Signal" in the datasheet.

I would solely use the information contained in v4l2_mbus_framefmt. You
could use the frame height for instance to detect the type of standard.

> >>>> Later versions of the datasheet have also been updated to make it clear
> >>>> that FLD register should be set to 0 when dealing with none interlaced
> >>>> field formats.
> >>>> 
> >>>> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> >>>> ---
> >>>>  drivers/media/platform/rcar-vin/rcar-csi2.c | 33 +++++++++++++++++++--
> >>>>  1 file changed, 30 insertions(+), 3 deletions(-)
> >>>> 
> >>>> diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
> >>>> index f3099f3e536d808a..664d3784be2b9db9 100644
> >>>> --- a/drivers/media/platform/rcar-vin/rcar-csi2.c
> >>>> +++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
> >>>> @@ -361,6 +361,7 @@ struct rcar_csi2 {
> >>>>  	struct v4l2_subdev *remote;
> >>>>  
> >>>>  	struct v4l2_mbus_framefmt mf;
> >>>> +	v4l2_std_id std;
> >>>>  
> >>>>  	struct mutex lock;
> >>>>  	int stream_count;
> >>>> @@ -389,6 +390,22 @@ static void rcsi2_write(struct rcar_csi2 *priv, unsigned int reg, u32 data)
> >>>>  	iowrite32(data, priv->base + reg);
> >>>>  }
> >>>>  
> >>>> +static int rcsi2_s_std(struct v4l2_subdev *sd, v4l2_std_id std)
> >>>> +{
> >>>> +	struct rcar_csi2 *priv = sd_to_csi2(sd);
> >>>> +
> >>>> +	priv->std = std;
> >>>> +	return 0;
> >>>> +}
> >>>> +
> >>>> +static int rcsi2_g_std(struct v4l2_subdev *sd, v4l2_std_id *std)
> >>>> +{
> >>>> +	struct rcar_csi2 *priv = sd_to_csi2(sd);
> >>>> +
> >>>> +	*std = priv->std;
> >>>> +	return 0;
> >>>> +}
> >>>> +
> >>>>  static void rcsi2_standby_mode(struct rcar_csi2 *priv, int on)
> >>>>  {
> >>>>  	if (!on) {
> >>>> @@ -475,7 +492,7 @@ static int rcsi2_calc_mbps(struct rcar_csi2 *priv, unsigned int bpp)
> >>>>  static int rcsi2_start_receiver(struct rcar_csi2 *priv)
> >>>>  {
> >>>>  	const struct rcar_csi2_format *format;
> >>>> -	u32 phycnt, vcdt = 0, vcdt2 = 0;
> >>>> +	u32 phycnt, vcdt = 0, vcdt2 = 0, fld = 0;
> >>>>  	unsigned int i;
> >>>>  	int mbps, ret;
> >>>>  
> >>>> @@ -507,6 +524,15 @@ static int rcsi2_start_receiver(struct rcar_csi2 *priv)
> >>>>  			vcdt2 |= vcdt_part << ((i % 2) * 16);
> >>>>  	}
> >>>>  
> >>>> +	if (priv->mf.field != V4L2_FIELD_NONE) {
> >>>> +		fld =  FLD_FLD_EN4 | FLD_FLD_EN3 | FLD_FLD_EN2 | FLD_FLD_EN;
> >>>> +
> >>>> +		if (priv->std & V4L2_STD_525_60)
> >>>> +			fld |= FLD_FLD_NUM(2);
> >>>> +		else
> >>>> +			fld |= FLD_FLD_NUM(1);
> >>>> +	}
> >>>> +
> >>>>  	phycnt = PHYCNT_ENABLECLK;
> >>>>  	phycnt |= (1 << priv->lanes) - 1;
> >>>>  
> >>>> @@ -519,8 +545,7 @@ static int rcsi2_start_receiver(struct rcar_csi2 *priv)
> >>>>  	rcsi2_write(priv, PHTC_REG, 0);
> >>>>  
> >>>>  	/* Configure */
> >>>> -	rcsi2_write(priv, FLD_REG, FLD_FLD_NUM(2) | FLD_FLD_EN4 |
> >>>> -		    FLD_FLD_EN3 | FLD_FLD_EN2 | FLD_FLD_EN);
> >>>> +	rcsi2_write(priv, FLD_REG, fld);
> >>>>  	rcsi2_write(priv, VCDT_REG, vcdt);
> >>>>  	if (vcdt2)
> >>>>  		rcsi2_write(priv, VCDT2_REG, vcdt2);
> >>>> @@ -662,6 +687,8 @@ static int rcsi2_get_pad_format(struct v4l2_subdev *sd,
> >>>>  }
> >>>>  
> >>>>  static const struct v4l2_subdev_video_ops rcar_csi2_video_ops = {
> >>>> +	.s_std = rcsi2_s_std,
> >>>> +	.g_std = rcsi2_g_std,
> >>>>  	.s_stream = rcsi2_s_stream,
> >>>>  };
> >>>>  

-- 
Regards,

Laurent Pinchart