Date:   Tue, 21 Feb 2017 17:54:14 +0200
From:   Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
To:     Ramiro Oliveira <Ramiro.Oliveira@...opsys.com>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <devicetree@...r.kernel.org>
CC:     <CARLOS.PALMINHA@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Pali Rohár <pali.rohar@...il.com>,
        Pavel Machek <pavel@....cz>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Rob Herring <robh+dt@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Steve Longerbeam <slongerbeam@...il.com>
Subject: Re: [PATCH v9 2/2] Add support for OV5647 sensor.

Hi Ramiro,

please find some review comments below.

On 02/17/2017 03:14 PM, Ramiro Oliveira wrote:
> The OV5647 sensor from Omnivision supports up to 2592x1944 @ 15 fps, RAW 8
> and RAW 10 output formats, and MIPI CSI-2 interface.
> 
> The driver adds support for 640x480 RAW 8.
> 
> Signed-off-by: Ramiro Oliveira <roliveir@...opsys.com>
> ---

[snip]

> +
> +struct ov5647 {
> +	struct v4l2_subdev		sd;
> +	struct media_pad		pad;
> +	struct mutex			lock;
> +	struct v4l2_mbus_framefmt	format;
> +	unsigned int			width;
> +	unsigned int			height;
> +	int				power_count;
> +	struct clk			*xclk;
> +	/* External clock frequency currently supported is 30MHz */
> +	u32				xclk_freq;

See a comment about 25MHz vs 30MHz below.

Also I assume you can remove 'xclk_freq' from the struct fields,
it can be replaced by a local variable.

> +};

[snip]

> +
> +static int ov5647_read(struct v4l2_subdev *sd, u16 reg, u8 *val)
> +{
> +	int ret;
> +	unsigned char data_w[2] = { reg >> 8, reg & 0xff };
> +	struct i2c_client *client = v4l2_get_subdevdata(sd);
> +
> +	ret = i2c_master_send(client, data_w, 2);
> +	if (ret < 0) {
> +		dev_dbg(&client->dev, "%s: i2c read error, reg: %x\n",

s/i2c read error/i2c write error/

> +			__func__, reg);
> +		return ret;
> +	}
> +
> +	ret = i2c_master_recv(client, val, 1);
> +	if (ret < 0)
> +		dev_dbg(&client->dev, "%s: i2c read error, reg: %x\n",
> +				__func__, reg);
> +
> +	return ret;
> +

Please remove the empty line above.

> +}
> +
> +static int ov5647_write_array(struct v4l2_subdev *sd,
> +				struct regval_list *regs, int array_size)
> +{
> +	int i = 0, ret;

Assignment of 'i' on declaration is not needed, please remove.

> +
> +	for (i = 0; i < array_size; i++) {
> +		ret = ov5647_write(sd, regs[i].addr, regs[i].data);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int ov5647_set_virtual_channel(struct v4l2_subdev *sd, int channel)
> +{
> +	u8 channel_id;
> +	int ret;
> +
> +	ret = ov5647_read(sd, 0x4814, &channel_id);
> +	if (ret < 0)
> +		return ret;
> +
> +	channel_id &= ~(3 << 6);
> +	return ov5647_write(sd, 0x4814, channel_id | (channel << 6));
> +}
> +
> +static int ov5647_stream_on(struct v4l2_subdev *sd)
> +{
> +	struct i2c_client *client = v4l2_get_subdevdata(sd);
> +
> +	ov5647_write(sd, 0x4202, 0x00);

Should you add a check of the returned value?

> +
> +	dev_dbg(&client->dev, "Stream on");

I would suggest to remove dev_dbg(), because ftrace will report to a user,
when this function is called.

Also dev_dbg() in the middle of two I2C transfers in a row looks as being
placed improperly.

> +
> +	return ov5647_write(sd, 0x300D, 0x00);
> +}
> +
> +static int ov5647_stream_off(struct v4l2_subdev *sd)
> +{
> +	struct i2c_client *client = v4l2_get_subdevdata(sd);
> +
> +	ov5647_write(sd, 0x4202, 0x0f);

Should you add a check of the returned value?

> +
> +	dev_dbg(&client->dev, "Stream off");

I would suggest to remove dev_dbg(), because ftrace will report to a user,
when this function is called.

Also dev_dbg() in the middle of two I2C transfers in a row looks as being
placed improperly.

> +
> +	return ov5647_write(sd, 0x300D, 0x01);
> +}
> +
> +static int set_sw_standby(struct v4l2_subdev *sd, bool standby)
> +{
> +	int ret;
> +	u8 rdval;
> +
> +	ret = ov5647_read(sd, 0x0100, &rdval);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (standby)
> +		rdval &= ~0x01;
> +	else
> +		rdval |= 0x01;
> +
> +	return ov5647_write(sd, 0x0100, rdval);
> +}
> +
> +static int __sensor_init(struct v4l2_subdev *sd)
> +{
> +	int ret;
> +	u8 resetval;
> +	u8 rdval;

It could be possible to put declarations of 'resetval' and 'rdval' on the same line.

> +	struct i2c_client *client = v4l2_get_subdevdata(sd);
> +
> +	dev_dbg(&client->dev, "sensor init\n");
> +
> +	ret = ov5647_read(sd, 0x0100, &rdval);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ov5647_write_array(sd, ov5647_640x480,
> +					ARRAY_SIZE(ov5647_640x480));
> +	if (ret < 0) {
> +		dev_err(&client->dev, "write sensor default regs error\n");
> +		return ret;
> +	}
> +
> +	ret = ov5647_set_virtual_channel(sd, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ov5647_read(sd, 0x0100, &resetval);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (!(resetval & 0x01)) {
> +		dev_err(&client->dev, "Device was in SW standby");
> +		ret = ov5647_write(sd, 0x0100, 0x01);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return ov5647_write(sd, 0x4800, 0x04);
> +}
> +
> +static int sensor_power(struct v4l2_subdev *sd, int on)
> +{
> +	int ret;
> +	struct ov5647 *ov5647 = to_state(sd);
> +	struct i2c_client *client = v4l2_get_subdevdata(sd);
> +
> +	ret = 0;
> +	mutex_lock(&ov5647->lock);
> +
> +	if (on && !ov5647->power_count)	{
> +		dev_dbg(&client->dev, "OV5647 power on\n");
> +
> +		clk_set_rate(ov5647->xclk, ov5647->xclk_freq);

Now clk_set_rate() is redundant, please remove it.

If once it is needed again, please move it to the .probe function, so
it is called only once in the runtime.

> +
> +		ret = clk_prepare_enable(ov5647->xclk);

I wonder would it be possible to unload the driver or to unbind the device
and leave the clock unintentionally enabled? If yes, then this is a bug.

> +		if (ret < 0) {
> +			dev_err(&client->dev, "clk prepare enable failed\n");
> +			goto out;
> +		}
> +
> +		ret = ov5647_write_array(sd, sensor_oe_enable_regs,
> +				ARRAY_SIZE(sensor_oe_enable_regs));
> +		if (ret < 0) {
> +			clk_disable_unprepare(ov5647->xclk);
> +			dev_err(&client->dev,
> +				"write sensor_oe_enable_regs error\n");
> +			goto out;
> +		}
> +
> +		ret = __sensor_init(sd);
> +		if (ret < 0) {
> +			clk_disable_unprepare(ov5647->xclk);
> +			dev_err(&client->dev,
> +				"Camera not available, check Power\n");
> +			goto out;
> +		}
> +	} else if (!on && ov5647->power_count == 1) {
> +		dev_dbg(&client->dev, "OV5647 power off\n");
> +
> +		dev_dbg(&client->dev, "disable oe\n");

One of two dev_dbg()'s above is apparently redundant.

> +		ret = ov5647_write_array(sd, sensor_oe_disable_regs,
> +				ARRAY_SIZE(sensor_oe_disable_regs));
> +
> +		if (ret < 0)
> +			dev_dbg(&client->dev, "disable oe failed\n");
> +
> +		ret = set_sw_standby(sd, true);
> +
> +		if (ret < 0)
> +			dev_dbg(&client->dev, "soft stby failed\n");
> +
> +		clk_disable_unprepare(ov5647->xclk);
> +	}
> +
> +	/* Update the power count. */
> +	ov5647->power_count += on ? 1 : -1;
> +	WARN_ON(ov5647->power_count < 0);
> +
> +out:
> +	mutex_unlock(&ov5647->lock);
> +
> +	return ret;
> +}
> +

[snip]

> +
> +static int ov5647_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct device *dev = &client->dev;
> +	struct ov5647 *sensor;
> +	int ret;
> +	struct v4l2_subdev *sd;
> +
> +	sensor = devm_kzalloc(dev, sizeof(*sensor), GFP_KERNEL);
> +	if (sensor == NULL)

if (!sensor) is a bit shorter.

> +		return -ENOMEM;
> +
> +	/* get system clock (xclk) */
> +	sensor->xclk = devm_clk_get(dev, "xclk");
> +	if (IS_ERR(sensor->xclk)) {
> +		dev_err(dev, "could not get xclk");
> +		return PTR_ERR(sensor->xclk);
> +	}
> +
> +	sensor->xclk_freq = clk_get_rate(sensor->xclk);
> +	if (sensor->xclk_freq != 25000000) {

A comment in "struct ov5647" declaration says about 30MHz, which one is correct?

> +		dev_err(dev, "Unsupported clock frequency: %u\n",
> +			sensor->xclk_freq);
> +		return -EINVAL;
> +	}
> +
> +	mutex_init(&sensor->lock);
> +
> +	sd = &sensor->sd;
> +	v4l2_i2c_subdev_init(sd, client, &subdev_ops);
> +	sensor->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
> +
> +	sensor->pad.flags = MEDIA_PAD_FL_SOURCE;
> +	sd->entity.function = MEDIA_ENT_F_CAM_SENSOR;
> +	ret = media_entity_pads_init(&sd->entity, 1, &sensor->pad);
> +	if (ret < 0)
> +		goto mutex_remove;
> +
> +	ret = ov5647_detect(sd);
> +	if (ret < 0)
> +		goto error;
> +
> +	ret = v4l2_async_register_subdev(sd);
> +	if (ret < 0)
> +		goto error;
> +
> +	dev_dbg(&client->dev, "OmniVision OV5647 camera driver probed\n");
> +	return 0;
> +error:
> +	media_entity_cleanup(&sd->entity);
> +mutex_remove:
> +	mutex_destroy(&sensor->lock);
> +	return ret;
> +}
> +

[snip]

The driver looks good in general IMO.

--
With best wishes,
Vladimir

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