Re: [PATCH v9 13/28] rcar-vin: fix handling of single field frames (top, bottom and alternate fields)

Laurent Pinchart
2017-12-08T09:35:02Z

Hi Niklas,

Thank you for the patch.

On Friday, 8 December 2017 03:08:27 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. For sources using
> this field format instead use the VIN hardware feature of combining the
> fields to an interlaced format. This mode of operation was previously
> the default behavior and ALTERNATING was only delivered to user-space if
> explicitly requested. Allowing this to be explicitly requested was a
> mistake and was never properly tested and never worked due to the
> constraints put on the field format when it comes to sequence numbers and
> timestamps etc.

I'm puzzled, why can't we support V4L2_FIELD_ALTERNATE if we can support
V4L2_FIELD_TOP and V4L2_FIELD_BOTTOM ? I don't dispute the fact that the
currently implemented logic might be wrong (although I haven't double-checked
that), but what prevents us from implementing it correctly ?

> 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 | 48 ++++++++++----------------
> 2 files changed, 19 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-dma.c
> b/drivers/media/platform/rcar-vin/rcar-dma.c index
> 7be5080f742825fb..e6478088d9464221 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
> 9cf9ff48ac1e2f4f..37fe1f6c646b0ea3 100644
> --- a/drivers/media/platform/rcar-vin/rcar-v4l2.c
> +++ b/drivers/media/platform/rcar-vin/rcar-v4l2.c
> @@ -102,6 +102,24 @@ static int rvin_get_sd_format(struct rvin_dev *vin,
> struct v4l2_pix_format *pix) 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:
> + /* Use VIN hardware to combine the two fields */
> + fmt.format.field = V4L2_FIELD_INTERLACED;
> + fmt.format.height *= 2;
> + break;

I don't think this is right. If V4L2_FIELD_ALTERNATE isn't supported it should
be rejected in the set format handler, or rather this logic should be moved
there. It doesn't belong here, rvin_get_sd_format() should only be called with
a validated and supported field.

Furthermore treating the pix parameter of this function as both input and
output seems very confusing to me. If you want to extend rvin_get_sd_format()
beyond just getting the format from the subdev then please document the
function with kerneldoc, and let's try to make its API clear.

> + default:
> + vin->format.field = V4L2_FIELD_NONE;
> + break;
> + }
> +
> v4l2_fill_pix_format(pix, &fmt.format);
>
> return 0;
> @@ -115,33 +133,6 @@ static int rvin_reset_format(struct rvin_dev *vin)
> if (ret)
> return ret;
>
> - /*
> - * 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;
> - }
> -
> vin->crop.top = vin->crop.left = 0;
> vin->crop.width = vin->format.width;
> vin->crop.height = vin->format.height;
> @@ -226,9 +217,6 @@ static int __rvin_try_format(struct rvin_dev *vin,
> 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:

--
Regards,

Laurent Pinchart