Re: [PATCH v10 10/30] rcar-vin: fix handling of single field frames (top, bottom and alternate fields)

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

Hi Niklas,

Thank you for the patch.

On Monday, 29 January 2018 18:34:15 EET Niklas Söderlund wrote:
> There was never proper support in the VIN driver to deliver ALTERNATING
> field format to user-space, remove this field option. The problem is
> that ALTERNATING filed order requires the sequence numbers of buffers
> returned to userspace to reflect if fields where dropped or not,
> something which is not possible with the VIN drivers capture logic.
> 
> The VIN driver can still capture from a video source which delivers
> frames in ALTERNATING field order, but needs to combine them using the
> VIN hardware into INTERLACED field order. Before this change if a source
> was delivering fields using ALTERNATE the driver would default to
> combining them using this hardware feature. Only if the user explicitly
> requested ALTERNATE filed order would incorrect frames be delivered.
> 
> The height should not be cut in half for the format for TOP or BOTTOM
> fields settings. This was a mistake and it was made visible by the
> scaling refactoring. Correct behavior is that the user should request a
> frame size that fits the half height frame reflected in the field
> setting. If not the VIN will do its best to scale the top or bottom to
> the requested format and cropping and scaling do not work as expected.
> 
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
> ---
>  drivers/media/platform/rcar-vin/rcar-dma.c  | 15 +-------
>  drivers/media/platform/rcar-vin/rcar-v4l2.c | 53 ++++++++++++--------------
>  2 files changed, 24 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/media/platform/rcar-vin/rcar-dma.c
> b/drivers/media/platform/rcar-vin/rcar-dma.c index
> fd14be20a6604d7a..c8831e189d362c8b 100644
> --- a/drivers/media/platform/rcar-vin/rcar-dma.c
> +++ b/drivers/media/platform/rcar-vin/rcar-dma.c
> @@ -617,7 +617,6 @@ static int rvin_setup(struct rvin_dev *vin)
>  	case V4L2_FIELD_INTERLACED_BT:
>  		vnmc = VNMC_IM_FULL | VNMC_FOC;
>  		break;
> -	case V4L2_FIELD_ALTERNATE:
>  	case V4L2_FIELD_NONE:
>  		if (vin->continuous) {
>  			vnmc = VNMC_IM_ODD_EVEN;
> @@ -757,18 +756,6 @@ static int rvin_get_active_slot(struct rvin_dev *vin,
> u32 vnms) return 0;
>  }
> 
> -static enum v4l2_field rvin_get_active_field(struct rvin_dev *vin, u32
> vnms)
> -{
> -	if (vin->format.field == V4L2_FIELD_ALTERNATE) {
> -		/* If FS is set it's a Even field */
> -		if (vnms & VNMS_FS)
> -			return V4L2_FIELD_BOTTOM;
> -		return V4L2_FIELD_TOP;
> -	}
> -
> -	return vin->format.field;
> -}
> -
>  static void rvin_set_slot_addr(struct rvin_dev *vin, int slot, dma_addr_t
> addr) {
>  	const struct rvin_video_format *fmt;
> @@ -941,7 +928,7 @@ static irqreturn_t rvin_irq(int irq, void *data)
>  		goto done;
> 
>  	/* Capture frame */
> -	vin->queue_buf[slot]->field = rvin_get_active_field(vin, vnms);
> +	vin->queue_buf[slot]->field = vin->format.field;
>  	vin->queue_buf[slot]->sequence = sequence;
>  	vin->queue_buf[slot]->vb2_buf.timestamp = ktime_get_ns();
>  	vb2_buffer_done(&vin->queue_buf[slot]->vb2_buf, VB2_BUF_STATE_DONE);
> diff --git a/drivers/media/platform/rcar-vin/rcar-v4l2.c
> b/drivers/media/platform/rcar-vin/rcar-v4l2.c index
> 4d5be2d0c79c9c9a..9f7902d29c62e205 100644
> --- a/drivers/media/platform/rcar-vin/rcar-v4l2.c
> +++ b/drivers/media/platform/rcar-vin/rcar-v4l2.c
> @@ -103,6 +103,28 @@ static int rvin_get_source_format(struct rvin_dev *vin,
> if (ret)
>  		return ret;
> 
> +	switch (fmt.format.field) {
> +	case V4L2_FIELD_TOP:
> +	case V4L2_FIELD_BOTTOM:
> +	case V4L2_FIELD_NONE:
> +	case V4L2_FIELD_INTERLACED_TB:
> +	case V4L2_FIELD_INTERLACED_BT:
> +	case V4L2_FIELD_INTERLACED:
> +		break;
> +	case V4L2_FIELD_ALTERNATE:
> +		/*
> +		 * Driver do not (yet) support outputting ALTERNATE to a
> +		 * userspace. It dose support outputting INTERLACED so use

s/dose/does/

> +		 * the VIN hardware to combine the two fields.
> +		 */
> +		fmt.format.field = V4L2_FIELD_INTERLACED;
> +		fmt.format.height *= 2;
> +		break;

I don't like this much. The rvin_get_source_format() function is supposed to 
return the media bus format for the bus between the source and the VIN. It's 
the caller that should take the field limitations into account, otherwise you 
end up with a mix of source and VIN data in the same structure.

> +	default:
> +		vin->format.field = V4L2_FIELD_NONE;
> +		break;
> +	}
> +
>  	memcpy(mbus_fmt, &fmt.format, sizeof(*mbus_fmt));
> 
>  	return 0;
> @@ -139,33 +161,6 @@ static int rvin_reset_format(struct rvin_dev *vin)
> 
>  	v4l2_fill_pix_format(&vin->format, &source_fmt);
> 
> -	/*
> -	 * If the subdevice uses ALTERNATE field mode and G_STD is
> -	 * implemented use the VIN HW to combine the two fields to
> -	 * one INTERLACED frame. The ALTERNATE field mode can still
> -	 * be requested in S_FMT and be respected, this is just the
> -	 * default which is applied at probing or when S_STD is called.
> -	 */
> -	if (vin->format.field == V4L2_FIELD_ALTERNATE &&
> -	    v4l2_subdev_has_op(vin_to_source(vin), video, g_std))
> -		vin->format.field = V4L2_FIELD_INTERLACED;
> -
> -	switch (vin->format.field) {
> -	case V4L2_FIELD_TOP:
> -	case V4L2_FIELD_BOTTOM:
> -	case V4L2_FIELD_ALTERNATE:
> -		vin->format.height /= 2;
> -		break;
> -	case V4L2_FIELD_NONE:
> -	case V4L2_FIELD_INTERLACED_TB:
> -	case V4L2_FIELD_INTERLACED_BT:
> -	case V4L2_FIELD_INTERLACED:
> -		break;
> -	default:
> -		vin->format.field = V4L2_FIELD_NONE;
> -		break;
> -	}
> -
>  	ret = rvin_reset_crop_compose(vin);
>  	if (ret)
>  		return ret;
> @@ -243,12 +238,10 @@ static int __rvin_try_format(struct rvin_dev *vin,
>  	if (ret)
>  		return ret;
> 
> +	/* Reject ALTERNATE  until support is added to the driver */
>  	switch (pix->field) {
>  	case V4L2_FIELD_TOP:
>  	case V4L2_FIELD_BOTTOM:
> -	case V4L2_FIELD_ALTERNATE:
> -		pix->height /= 2;
> -		break;
>  	case V4L2_FIELD_NONE:
>  	case V4L2_FIELD_INTERLACED_TB:
>  	case V4L2_FIELD_INTERLACED_BT:

You will then set the field to V4L2_FIELD_NONE, but the source will still 
provide V4L2_FIELD_ALTERNATE. What will happen in the VIN, what will it 
produce ?

-- 
Regards,

Laurent Pinchart