Message-ID: <20180103101131.r3njszxr3bcwafdt@valkosipuli.retiisi.org.uk>
Date:   Wed, 3 Jan 2018 12:11:32 +0200
From:   Sakari Ailus <sakari.ailus@....fi>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>
Cc:     corbet@....net, mchehab@...nel.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] v4l2: i2c: ov7670: Implement OF mbus configuration

Hi Jacopo,

Please see my comments below.

On Tue, Jan 02, 2018 at 04:03:53PM +0100, Jacopo Mondi wrote:
> ov7670 driver supports two optional properties supplied through platform
> data, but currently does not support any standard video interface
> property.
> 
> Add support through OF parsing for 2 generic properties (vsync and hsync
> polarities) and for two custom properties already supported by platform
> data.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> ---
> 
> I have made sure signal polarities gets properly changed using a scope and
> capturing images with negative polarities using CEU capture interface.
> Also verified with a scope that pixel clock gets suppressed on horizontal
> blankings as well when "ov7670,pclk-hb-disable" property is specified.
> 
> Thanks
>    j
> ---
> 
>  .../devicetree/bindings/media/i2c/ov7670.txt       |  12 +++
>  drivers/media/i2c/ov7670.c                         | 101 +++++++++++++++++++--
>  2 files changed, 106 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/ov7670.txt b/Documentation/devicetree/bindings/media/i2c/ov7670.txt
> index 826b656..c005453 100644
> --- a/Documentation/devicetree/bindings/media/i2c/ov7670.txt
> +++ b/Documentation/devicetree/bindings/media/i2c/ov7670.txt
> @@ -9,11 +9,20 @@ Required Properties:
>  - clocks: reference to the xclk input clock.
>  - clock-names: should be "xclk".
> 
> +The following properties, as defined by "video-interfaces.txt", are supported:
> +- hsync-active: active state of the HSYNC signal, 0/1 for LOW/HIGH respectively.
> +- vsync-active: active state of the VSYNC signal, 0/1 for LOW/HIGH respectively.
> +
> +Default is high active state for both vsync and hsync signals.
> +
>  Optional Properties:
>  - reset-gpios: reference to the GPIO connected to the resetb pin, if any.
>    Active is low.
>  - powerdown-gpios: reference to the GPIO connected to the pwdn pin, if any.
>    Active is high.
> +- ov7670,pll-bypass: set to 1 to bypass PLL for pixel clock generation.

Is this something that should be specified using a device specific
property?

It looks like a rather crude way to configure the sensor's internal clock
tree. Is this something that could be deduced from the external clock
frequency? The check for the clock frequency seems very coarse and more or
less satisfies the device's input clock frequency limits (between 10 and 48
MHz).

> +- ov7670,pclk-hb-disable: set to 1 to suppress pixel clock output signal during
> +  horizontal blankings.

Please separate the DT bindings from driver changes, and cc the devicetree
list.

> 
>  The device node must contain one 'port' child node for its digital output
>  video port, in accordance with the video interface bindings defined in
> @@ -34,6 +43,9 @@ Example:
>  			assigned-clocks = <&pck0>;
>  			assigned-clock-rates = <25000000>;
> 
> +			vsync-active = <0>;
> +			pclk-sample = <1>;
> +
>  			port {
>  				ov7670_0: endpoint {
>  					remote-endpoint = <&isi_0>;
> diff --git a/drivers/media/i2c/ov7670.c b/drivers/media/i2c/ov7670.c
> index 950a0ac..a42bee7 100644
> --- a/drivers/media/i2c/ov7670.c
> +++ b/drivers/media/i2c/ov7670.c
> @@ -11,6 +11,7 @@
>   * Public License, version 2.
>   */
>  #include <linux/clk.h>
> +#include <linux/fwnode.h>

media/v4l2-fwnode.h includes linux/fwnode.h.

>  #include <linux/init.h>
>  #include <linux/module.h>
>  #include <linux/slab.h>
> @@ -21,6 +22,7 @@
>  #include <linux/gpio/consumer.h>
>  #include <media/v4l2-device.h>
>  #include <media/v4l2-ctrls.h>
> +#include <media/v4l2-fwnode.h>
>  #include <media/v4l2-mediabus.h>
>  #include <media/v4l2-image-sizes.h>
>  #include <media/i2c/ov7670.h>
> @@ -237,6 +239,7 @@ struct ov7670_info {
>  	struct clk *clk;
>  	struct gpio_desc *resetb_gpio;
>  	struct gpio_desc *pwdn_gpio;
> +	unsigned int mbus_config;	/* Media bus configuration flags */
>  	int min_width;			/* Filter out smaller sizes */
>  	int min_height;			/* Filter out smaller sizes */
>  	int clock_speed;		/* External clock speed (MHz) */
> @@ -995,7 +998,7 @@ static int ov7670_set_fmt(struct v4l2_subdev *sd,
>  #ifdef CONFIG_VIDEO_V4L2_SUBDEV_API
>  	struct v4l2_mbus_framefmt *mbus_fmt;
>  #endif
> -	unsigned char com7;
> +	unsigned char com7, com10 = 0;
>  	int ret;
> 
>  	if (format->pad)
> @@ -1027,6 +1030,18 @@ static int ov7670_set_fmt(struct v4l2_subdev *sd,
>  	com7 = ovfmt->regs[0].value;
>  	com7 |= wsize->com7_bit;
>  	ov7670_write(sd, REG_COM7, com7);
> +
> +	/*
> +	 * Configure the media bus through COM10 register
> +	 */
> +	if (info->mbus_config & V4L2_MBUS_VSYNC_ACTIVE_LOW)
> +		com10 |= COM10_VS_NEG;
> +	if (info->mbus_config & V4L2_MBUS_HSYNC_ACTIVE_LOW)
> +		com10 |= COM10_HREF_REV;
> +	if (info->pclk_hb_disable)
> +		com10 |= COM10_PCLK_HB;
> +	ov7670_write(sd, REG_COM10, com10);

How about checking the return value here?

> +
>  	/*
>  	 * Now write the rest of the array.  Also store start/stops
>  	 */
> @@ -1036,6 +1051,9 @@ static int ov7670_set_fmt(struct v4l2_subdev *sd,
>  	ret = 0;
>  	if (wsize->regs)
>  		ret = ov7670_write_array(sd, wsize->regs);
> +	if (ret)
> +		return ret;

That looks a bit confusing. How about checking it only if it's set? Or
change ov7670_write_array() to accept NULL register list (and return zero)?

> +
>  	info->fmt = ovfmt;
> 
>  	/*
> @@ -1048,8 +1066,10 @@ static int ov7670_set_fmt(struct v4l2_subdev *sd,
>  	 * to write it unconditionally, and that will make the frame
>  	 * rate persistent too.
>  	 */
> -	if (ret == 0)
> -		ret = ov7670_write(sd, REG_CLKRC, info->clkrc);
> +	ret = ov7670_write(sd, REG_CLKRC, info->clkrc);
> +	if (ret)
> +		return ret;
> +
>  	return 0;
>  }
> 
> @@ -1658,6 +1678,71 @@ static int ov7670_init_gpio(struct i2c_client *client, struct ov7670_info *info)
>  	return 0;
>  }
> 
> +/*
> + * ov7670_parse_dt() - Parse device tree to collect mbus configuration
> + *			properties
> + */
> +static int ov7670_parse_dt(struct device *dev,
> +			   struct ov7670_info *info)
> +{
> +	struct fwnode_handle *fwnode = dev_fwnode(dev);
> +	struct v4l2_fwnode_endpoint bus_cfg;
> +	struct fwnode_handle *ep;
> +	struct device_node *dep;
> +	u32 propval;
> +	int ret;
> +
> +	if (!fwnode)
> +		return -EINVAL;
> +
> +	ep = fwnode_graph_get_next_endpoint(fwnode, NULL);
> +	if (!ep)
> +		return -EINVAL;
> +
> +	ret = v4l2_fwnode_endpoint_parse(ep, &bus_cfg);
> +	if (ret) {
> +		fwnode_handle_put(fwnode);
> +		return ret;
> +	}
> +
> +	/* Any CSI-2 property set? */
> +	if (bus_cfg.bus_type != V4L2_MBUS_PARALLEL) {
> +		fwnode_handle_put(fwnode);
> +		return -EINVAL;
> +	}
> +	info->mbus_config = bus_cfg.bus.parallel.flags;
> +	fwnode_handle_put(fwnode);
> +
> +	/* Parse custom OF properties. */
> +	dep = to_of_node(ep);
> +	ret = of_property_read_u32(dep, "ov7670,pclk-hb-disable", &propval);

You could use fwnode_property_read_u32() on the fwnode without converting
it to OF node.

> +	if (ret < 0 && ret != -EINVAL) {
> +		dev_err(dev,
> +			"Unable to parse property \"ov7670,pclk-hb-disable\"\n");
> +		fwnode_handle_put(ep);
> +		return ret;
> +	}
> +	if (ret == 0 && propval)
> +		info->pclk_hb_disable = true;
> +	else
> +		info->pclk_hb_disable = false;
> +
> +	ret = of_property_read_u32(dep, "ov7670,pll-bypass", &propval);
> +	if (ret < 0 && ret != -EINVAL) {
> +		dev_err(dev,
> +			"Unable to parse property \"ov7670,pll-bypass\"\n");
> +		fwnode_handle_put(ep);
> +		return ret;
> +	}
> +	if (ret == 0 && propval)
> +		info->pll_bypass = true;
> +	else
> +		info->pll_bypass = false;
> +
> +	fwnode_handle_put(ep);

Newline here?

> +	return 0;
> +}
> +
>  static int ov7670_probe(struct i2c_client *client,
>  			const struct i2c_device_id *id)
>  {
> @@ -1678,7 +1763,12 @@ static int ov7670_probe(struct i2c_client *client,
>  #endif
> 
>  	info->clock_speed = 30; /* default: a guess */
> -	if (client->dev.platform_data) {
> +
> +	if (IS_ENABLED(CONFIG_OF) && client->dev.of_node) {

if (dev_fwnode(&client->dev))

> +		ret = ov7670_parse_dt(&client->dev, info);
> +		if (ret)
> +			return ret;
> +	} else if (client->dev.platform_data) {
>  		struct ov7670_config *config = client->dev.platform_data;
> 
>  		/*
> @@ -1745,9 +1835,6 @@ static int ov7670_probe(struct i2c_client *client,
>  	tpf.denominator = 30;
>  	info->devtype->set_framerate(sd, &tpf);
> 
> -	if (info->pclk_hb_disable)
> -		ov7670_write(sd, REG_COM10, COM10_PCLK_HB);
> -
>  	v4l2_ctrl_handler_init(&info->hdl, 10);
>  	v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
>  			V4L2_CID_BRIGHTNESS, 0, 255, 1, 128);

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@....fi

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