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Date:   Sun, 17 May 2020 00:51:03 +0300
From:   Sakari Ailus <sakari.ailus@iki.fi>
To:     Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Cc:     linux-renesas-soc@vger.kernel.org, linux-media@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Kieran Bingham <kieran.bingham@ideasonboard.com>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Jacopo Mondi <jacopo@jmondi.org>,
        Niklas =?iso-8859-1?Q?S=F6derlund?= 
        <niklas.soderlund@ragnatech.se>, Hans Verkuil <hverkuil@xs4all.nl>,
        Hyun Kwon <hyunk@xilinx.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Jacopo Mondi <jacopo+renesas@jmondi.org>,
        Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>,
        Niklas =?iso-8859-1?Q?S=F6derlund?= 
        <niklas.soderlund+renesas@ragnatech.se>
Subject: Re: [PATCH v9 2/4] media: i2c: Add MAX9286 driver
Message-ID: <20200516215103.GA857@valkosipuli.retiisi.org.uk>
References: <20200512155105.1068064-1-kieran.bingham+renesas@ideasonboard.com>
 <20200512155105.1068064-3-kieran.bingham+renesas@ideasonboard.com>
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Hi Kieran,

Thanks for the update.

On Tue, May 12, 2020 at 04:51:03PM +0100, Kieran Bingham wrote:

...

> +static int max9286_enum_mbus_code(struct v4l2_subdev *sd,
> +				  struct v4l2_subdev_pad_config *cfg,
> +				  struct v4l2_subdev_mbus_code_enum *code)
> +{
> +	if (code->pad || code->index > 0)
> +		return -EINVAL;
> +
> +	code->code = MEDIA_BUS_FMT_UYVY8_2X8;

Why UYVY8_2X8 and not UYVY8_1X16? In general, the single sample / pixel
variant of the format is generally used on the serial busses. This choice
was made when serial busses were introduced.

> +
> +	return 0;
> +}
> +
> +static struct v4l2_mbus_framefmt *
> +max9286_get_pad_format(struct max9286_priv *priv,
> +		       struct v4l2_subdev_pad_config *cfg,
> +		       unsigned int pad, u32 which)
> +{
> +	switch (which) {
> +	case V4L2_SUBDEV_FORMAT_TRY:
> +		return v4l2_subdev_get_try_format(&priv->sd, cfg, pad);
> +	case V4L2_SUBDEV_FORMAT_ACTIVE:
> +		return &priv->fmt[pad];
> +	default:
> +		return NULL;
> +	}
> +}
> +
> +static int max9286_set_fmt(struct v4l2_subdev *sd,
> +			   struct v4l2_subdev_pad_config *cfg,
> +			   struct v4l2_subdev_format *format)
> +{
> +	struct max9286_priv *priv = sd_to_max9286(sd);
> +	struct v4l2_mbus_framefmt *cfg_fmt;
> +
> +	if (format->pad >= MAX9286_SRC_PAD)
> +		return -EINVAL;

You can remove these checks; it's been already done by the caller.

...

> +static int max9286_parse_dt(struct max9286_priv *priv)
> +{
> +	struct device *dev = &priv->client->dev;
> +	struct device_node *i2c_mux;
> +	struct device_node *node = NULL;
> +	unsigned int i2c_mux_mask = 0;
> +
> +	of_node_get(dev->of_node);
> +	i2c_mux = of_find_node_by_name(dev->of_node, "i2c-mux");
> +	if (!i2c_mux) {
> +		dev_err(dev, "Failed to find i2c-mux node\n");
> +		of_node_put(dev->of_node);
> +		return -EINVAL;
> +	}
> +
> +	/* Identify which i2c-mux channels are enabled */
> +	for_each_child_of_node(i2c_mux, node) {
> +		u32 id = 0;
> +
> +		of_property_read_u32(node, "reg", &id);
> +		if (id >= MAX9286_NUM_GMSL)
> +			continue;
> +
> +		if (!of_device_is_available(node)) {
> +			dev_dbg(dev, "Skipping disabled I2C bus port %u\n", id);
> +			continue;
> +		}
> +
> +		i2c_mux_mask |= BIT(id);
> +	}
> +	of_node_put(node);
> +	of_node_put(i2c_mux);
> +
> +	/* Parse the endpoints */
> +	for_each_endpoint_of_node(dev->of_node, node) {
> +		struct max9286_source *source;
> +		struct of_endpoint ep;
> +
> +		of_graph_parse_endpoint(node, &ep);
> +		dev_dbg(dev, "Endpoint %pOF on port %d",
> +			ep.local_node, ep.port);
> +
> +		if (ep.port > MAX9286_NUM_GMSL) {
> +			dev_err(dev, "Invalid endpoint %s on port %d",
> +				of_node_full_name(ep.local_node), ep.port);
> +			continue;
> +		}
> +
> +		/* For the source endpoint just parse the bus configuration. */
> +		if (ep.port == MAX9286_SRC_PAD) {
> +			struct v4l2_fwnode_endpoint vep = {
> +				.bus_type = V4L2_MBUS_CSI2_DPHY
> +			};
> +			int ret;
> +
> +			ret = v4l2_fwnode_endpoint_parse(
> +					of_fwnode_handle(node), &vep);
> +			if (ret) {
> +				of_node_put(node);
> +				of_node_put(dev->of_node);
> +				return ret;
> +			}
> +
> +			if (vep.bus_type != V4L2_MBUS_CSI2_DPHY) {

This won't happen, the bus type will stay if you set it to a non-zero
value.

> +				dev_err(dev,
> +					"Media bus %u type not supported\n",
> +					vep.bus_type);
> +				v4l2_fwnode_endpoint_free(&vep);
> +				of_node_put(node);
> +				of_node_put(dev->of_node);
> +				return -EINVAL;
> +			}
> +
> +			priv->csi2_data_lanes =
> +				vep.bus.mipi_csi2.num_data_lanes;
> +			v4l2_fwnode_endpoint_free(&vep);

No need to call this unless you use v4l2_fwnode_endpoint_alloc_parse().

And as you don't, you also won't know which frequencies are known to be
safe to use. That said, perhaps where this device is used having a random
frequency on that bus could not be an issue. Perhaps.

> +
> +			continue;
> +		}
> +
> +		/* Skip if the corresponding GMSL link is unavailable. */
> +		if (!(i2c_mux_mask & BIT(ep.port)))
> +			continue;
> +
> +		if (priv->sources[ep.port].fwnode) {
> +			dev_err(dev,
> +				"Multiple port endpoints are not supported: %d",
> +				ep.port);
> +
> +			continue;
> +		}
> +
> +		source = &priv->sources[ep.port];
> +		source->fwnode = fwnode_graph_get_remote_endpoint(
> +						of_fwnode_handle(node));
> +		if (!source->fwnode) {
> +			dev_err(dev,
> +				"Endpoint %pOF has no remote endpoint connection\n",
> +				ep.local_node);
> +
> +			continue;
> +		}
> +
> +		priv->source_mask |= BIT(ep.port);
> +		priv->nsources++;
> +	}
> +	of_node_put(node);
> +	of_node_put(dev->of_node);
> +
> +	priv->route_mask = priv->source_mask;
> +
> +	return 0;
> +}

-- 
Kind regards,

Sakari Ailus