[PATCH v3] media: imx-csi: Skip first few frames from a BT.656 source

[PATCH v3] media: imx-csi: Skip first few frames from a BT.656 source

[Fabio Estevam]

From: Steve Longerbeam <slongerbeam@gmail.com>

Some BT.656 sensors (e.g. ADV718x) transmit frames with unstable BT.656
sync codes after initial power on. This confuses the imx CSI,resulting
in vertical and/or horizontal sync issues. Skip the first 20 frames
to avoid the unstable sync codes.

Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
[fabio: fixed checkpatch warning and increased the frame skipping to 20]
Signed-off-by: Fabio Estevam <festevam@gmail.com>
---
Changes since v2:
- Increase 'bad_frames' to 20 as 10 was not enough to avoid
the problem when using an NTSC camera.

 drivers/staging/media/imx/imx-media-csi.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/imx/imx-media-csi.c b/drivers/staging/media/imx/imx-media-csi.c
index e3bfd635a89a..6a94fff49bf6 100644
--- a/drivers/staging/media/imx/imx-media-csi.c
+++ b/drivers/staging/media/imx/imx-media-csi.c
@@ -750,9 +750,10 @@ static int csi_setup(struct csi_priv *priv)
 
 static int csi_start(struct csi_priv *priv)
 {
-	struct v4l2_fract *output_fi;
+	struct v4l2_fract *input_fi, *output_fi;
 	int ret;
 
+	input_fi = &priv->frame_interval[CSI_SINK_PAD];
 	output_fi = &priv->frame_interval[priv->active_output_pad];
 
 	/* start upstream */
@@ -761,6 +762,17 @@ static int csi_start(struct csi_priv *priv)
 	if (ret)
 		return ret;
 
+	/* Skip first few frames from a BT.656 source */
+	if (priv->upstream_ep.bus_type == V4L2_MBUS_BT656) {
+		u32 delay_usec, bad_frames = 20;
+
+		delay_usec = DIV_ROUND_UP_ULL((u64)USEC_PER_SEC *
+			input_fi->numerator * bad_frames,
+			input_fi->denominator);
+
+		usleep_range(delay_usec, delay_usec + 1000);
+	}
+
 	if (priv->dest == IPU_CSI_DEST_IDMAC) {
 		ret = csi_idmac_start(priv);
 		if (ret)
-- 
2.25.1

Re: [PATCH v3] media: imx-csi: Skip first few frames from a BT.656 source

[Tim Harvey]

On Mon, May 17, 2021 at 7:29 AM Fabio Estevam <festevam@gmail.com> wrote:
>
> From: Steve Longerbeam <slongerbeam@gmail.com>
>
> Some BT.656 sensors (e.g. ADV718x) transmit frames with unstable BT.656
> sync codes after initial power on. This confuses the imx CSI,resulting
> in vertical and/or horizontal sync issues. Skip the first 20 frames
> to avoid the unstable sync codes.
>
> Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
> [fabio: fixed checkpatch warning and increased the frame skipping to 20]
> Signed-off-by: Fabio Estevam <festevam@gmail.com>
> ---
> Changes since v2:
> - Increase 'bad_frames' to 20 as 10 was not enough to avoid
> the problem when using an NTSC camera.
>
>  drivers/staging/media/imx/imx-media-csi.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/staging/media/imx/imx-media-csi.c b/drivers/staging/media/imx/imx-media-csi.c
> index e3bfd635a89a..6a94fff49bf6 100644
> --- a/drivers/staging/media/imx/imx-media-csi.c
> +++ b/drivers/staging/media/imx/imx-media-csi.c
> @@ -750,9 +750,10 @@ static int csi_setup(struct csi_priv *priv)
>
>  static int csi_start(struct csi_priv *priv)
>  {
> -       struct v4l2_fract *output_fi;
> +       struct v4l2_fract *input_fi, *output_fi;
>         int ret;
>
> +       input_fi = &priv->frame_interval[CSI_SINK_PAD];
>         output_fi = &priv->frame_interval[priv->active_output_pad];
>
>         /* start upstream */
> @@ -761,6 +762,17 @@ static int csi_start(struct csi_priv *priv)
>         if (ret)
>                 return ret;
>
> +       /* Skip first few frames from a BT.656 source */
> +       if (priv->upstream_ep.bus_type == V4L2_MBUS_BT656) {
> +               u32 delay_usec, bad_frames = 20;
> +
> +               delay_usec = DIV_ROUND_UP_ULL((u64)USEC_PER_SEC *
> +                       input_fi->numerator * bad_frames,
> +                       input_fi->denominator);
> +
> +               usleep_range(delay_usec, delay_usec + 1000);
> +       }
> +
>         if (priv->dest == IPU_CSI_DEST_IDMAC) {
>                 ret = csi_idmac_start(priv);
>                 if (ret)
> --
> 2.25.1
>

Reviewed-By: Tim Harvey <tharvey@gateworks.com>