linux-kernel - Re: [PATCH v2 2/3] media: i2c: ov772x: Add support for BT656 mode

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Message-ID: <20200806144511.6ajoqyynowglnbpm@uno.localdomain>
Date:   Thu, 6 Aug 2020 16:45:11 +0200
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Biju Das <biju.das.jz@...renesas.com>,
        Prabhakar <prabhakar.csengg@...il.com>,
        linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2 2/3] media: i2c: ov772x: Add support for BT656 mode

On Mon, Aug 03, 2020 at 12:39:12PM +0100, Lad Prabhakar wrote:
> Add support to read the bus-type and enable BT656 mode if needed.
>
> The driver defaults to parallel mode if bus-type is not specified in DT.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> Reviewed-by: Biju Das <biju.das.jz@...renesas.com>
> ---
>  drivers/media/i2c/ov772x.c | 40 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
>
> diff --git a/drivers/media/i2c/ov772x.c b/drivers/media/i2c/ov772x.c
> index 2cc6a678069a..2de9248e3689 100644
> --- a/drivers/media/i2c/ov772x.c
> +++ b/drivers/media/i2c/ov772x.c
> @@ -31,6 +31,7 @@
>  #include <media/v4l2-ctrls.h>
>  #include <media/v4l2-device.h>
>  #include <media/v4l2-event.h>
> +#include <media/v4l2-fwnode.h>
>  #include <media/v4l2-image-sizes.h>
>  #include <media/v4l2-subdev.h>
>
> @@ -434,6 +435,7 @@ struct ov772x_priv {
>  #ifdef CONFIG_MEDIA_CONTROLLER
>  	struct media_pad pad;
>  #endif
> +	struct v4l2_fwnode_endpoint ep;
>  };
>
>  /*
> @@ -574,6 +576,7 @@ static int ov772x_s_stream(struct v4l2_subdev *sd, int enable)
>  {
>  	struct i2c_client *client = v4l2_get_subdevdata(sd);
>  	struct ov772x_priv *priv = to_ov772x(sd);
> +	unsigned int val;
>  	int ret = 0;
>
>  	mutex_lock(&priv->lock);
> @@ -581,6 +584,22 @@ static int ov772x_s_stream(struct v4l2_subdev *sd, int enable)
>  	if (priv->streaming == enable)
>  		goto done;
>
> +	if (priv->ep.bus_type == V4L2_MBUS_BT656 && enable) {
> +		ret = regmap_read(priv->regmap, COM7, &val);
> +		if (ret)
> +			goto done;
> +		val |= ITU656_ON_OFF;
> +		ret = regmap_write(priv->regmap, COM7, val);
> +	} else if (priv->ep.bus_type == V4L2_MBUS_BT656 && !enable) {

is the !enable intentional ? (sorry I don't have access to the sensor
manual). If not, see below:

> +		ret = regmap_read(priv->regmap, COM7, &val);
> +		if (ret)
> +			goto done;
> +		val &= ~ITU656_ON_OFF;
> +		ret = regmap_write(priv->regmap, COM7, val);
> +	}
> +	if (ret)
> +		goto done;

Could you write this as:

static int ov772x_s_stream(struct v4l2_subdev *sd, int enable)
{
	struct i2c_client *client = v4l2_get_subdevdata(sd);
	struct ov772x_priv *priv = to_ov772x(sd);
	int ret = 0;

	mutex_lock(&priv->lock);

	if (priv->streaming == enable)
		goto done;

	if (enable) {
		ret = regmap_read(priv->regmap, COM7, &val);
		if (ret)
			goto done;

	        if (priv->ep.bus_type == V4L2_MBUS_BT656)
		        val |= ITU656_ON_OFF;
                else /* if you accept my suggestion to consider othe
                        bus types as errors */
		        val &= ~ITU656_ON_OFF;

		ret = regmap_write(priv->regmap, COM7, val);
		if (ret)
			goto done;

		dev_dbg(&client->dev, "format %d, win %s\n",
			priv->cfmt->code, priv->win->name);
	}

	ret = regmap_update_bits(priv->regmap, COM2, SOFT_SLEEP_MODE,
				 enable ? 0 : SOFT_SLEEP_MODE);
	if (ret)
		goto done;
	priv->streaming = enable;

done:
	mutex_unlock(&priv->lock);

	return ret;
}


>  	ret = regmap_update_bits(priv->regmap, COM2, SOFT_SLEEP_MODE,
>  				 enable ? 0 : SOFT_SLEEP_MODE);
>  	if (ret)
> @@ -1354,6 +1373,7 @@ static const struct v4l2_subdev_ops ov772x_subdev_ops = {
>
>  static int ov772x_probe(struct i2c_client *client)
>  {
> +	struct fwnode_handle *endpoint;
>  	struct ov772x_priv	*priv;
>  	int			ret;
>  	static const struct regmap_config ov772x_regmap_config = {
> @@ -1415,6 +1435,26 @@ static int ov772x_probe(struct i2c_client *client)
>  		goto error_clk_put;
>  	}
>
> +	endpoint = fwnode_graph_get_next_endpoint(dev_fwnode(&client->dev),
> +						  NULL);
> +	if (!endpoint) {
> +		dev_err(&client->dev, "endpoint node not found\n");
> +		ret = -EINVAL;
> +		goto error_clk_put;
> +	}
> +
> +	ret = v4l2_fwnode_endpoint_parse(endpoint, &priv->ep);
> +	fwnode_handle_put(endpoint);
> +	if (ret) {
> +		dev_err(&client->dev, "Could not parse endpoint\n");
> +		goto error_clk_put;
> +	}
> +
> +	/* fallback to parallel mode */
> +	if (priv->ep.bus_type != V4L2_MBUS_PARALLEL &&
> +	    priv->ep.bus_type != V4L2_MBUS_BT656)
> +		priv->ep.bus_type = V4L2_MBUS_PARALLEL;

shouldn't this be an error ? It's either the bus type has not been
specified on DT (which is fine, otherwise old DTB without that
properties will fail) and the bus identification routine implemented
in v4l2_fwnode_endpoint_parse() detected a bus type which is not
supported, hence the DT properties are wrong, and this should be an
error. If you plan to expand the parsing routine to support, say
bus-width and pclk polarity please break this out to a new function.

Thanks
   j

> +
>  	ret = ov772x_video_probe(priv);
>  	if (ret < 0)
>  		goto error_gpio_put;
> --
> 2.17.1
>