Re: [PATCH 2/4] media: ov2640: add primary dt support

[Josh Wu <josh.wu@atmel.com>]

Hi, Laurent

On 12/2/2014 6:33 AM, Laurent Pinchart wrote:
> Hi Josh,
>
> Thank you for the patch.
>
> On Friday 28 November 2014 18:28:25 Josh Wu wrote:
>> Add device tree support for ov2640.
>>
>> Cc:devicetree@vger.kernel.org
>> Signed-off-by: Josh Wu<josh.wu@atmel.com>
>> ---
>>   drivers/media/i2c/soc_camera/ov2640.c | 95 +++++++++++++++++++++++++++++---
>>   1 file changed, 89 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/media/i2c/soc_camera/ov2640.c
>> b/drivers/media/i2c/soc_camera/ov2640.c index 9ee910d..6506126 100644
>> --- a/drivers/media/i2c/soc_camera/ov2640.c
>> +++ b/drivers/media/i2c/soc_camera/ov2640.c
>> @@ -18,6 +18,8 @@
>>   #include <linux/i2c.h>
>>   #include <linux/slab.h>
>>   #include <linux/delay.h>
>> +#include <linux/gpio.h>
>> +#include <linux/of_gpio.h>
>>   #include <linux/v4l2-mediabus.h>
>>   #include <linux/videodev2.h>
>>
>> @@ -283,6 +285,10 @@ struct ov2640_priv {
>>   	u32	cfmt_code;
>>   	struct v4l2_clk			*clk;
>>   	const struct ov2640_win_size	*win;
>> +
>> +	struct soc_camera_subdev_desc	ssdd_dt;
>> +	int reset_pin;
>> +	int pwr_down_pin;
>>   };
>>
>>   /*
>> @@ -1047,6 +1053,70 @@ static struct v4l2_subdev_ops ov2640_subdev_ops = {
>>   	.video	= &ov2640_subdev_video_ops,
>>   };
>>
>> +/* OF probe functions */
>> +static int ov2640_hw_power(struct device *dev, int on)
>> +{
>> +	struct i2c_client *client = to_i2c_client(dev);
>> +	struct ov2640_priv *priv = to_ov2640(client);
>> +
>> +	dev_dbg(&client->dev, "%s: %s the camera\n",
>> +			__func__, on ? "ENABLE" : "DISABLE");
>> +
>> +	/* enable or disable the camera */
>> +	gpio_direction_output(priv->pwr_down_pin, !on);
> Isn't there a delay required to wake the chip up ?
I don't see any document mention a delay is needed when waked up.

>
>> +
>> +	return 0;
>> +}
>> +
>> +static int ov2640_hw_reset(struct device *dev)
>> +{
>> +	struct i2c_client *client = to_i2c_client(dev);
>> +	struct ov2640_priv *priv = to_ov2640(client);
>> +
> If the reset GPIO isn't specified you should return immediately without
> waiting 120ms.

I find some document that said the reset pulse need >= 3ms. So I think 
use 3~5ms is enough.

>
>> +	/* If enabled, give a reset impulse */
>> +	gpio_direction_output(priv->reset_pin, 0);
>> +	msleep(20);
> Please use usleep_range().

ok.
>
>> +	gpio_direction_output(priv->reset_pin, 1);
>> +	msleep(100);
> Is the reset delay documented somewhere ? 100ms seems pretty large to me.

It seems no need to wait another delay after the reset pulse is generated.
I will remove this line: msleep(100);
>> +
>> +	return 0;
>> +}
>> +
>> +static int ov2640_probe_dt(struct i2c_client *client,
>> +		struct ov2640_priv *priv)
>> +{
>> +	struct device_node *np = client->dev.of_node;
>> +	int ret;
>> +
>> +	priv->reset_pin = of_get_named_gpio(np, "reset-gpio", 0);
>> +	priv->pwr_down_pin = of_get_named_gpio(np, "power-down-gpio", 0);
>> +	if (!gpio_is_valid(priv->reset_pin) ||
>> +			!gpio_is_valid(priv->pwr_down_pin))
>> +		return -EINVAL;
>> +
>> +	ret = devm_gpio_request(&client->dev, priv->pwr_down_pin,
>> +			"power-down-pin");
>> +	if (ret < 0) {
>> +		dev_err(&client->dev, "request gpio pin %d failed\n",
>> +				priv->pwr_down_pin);
>> +		return ret;
>> +	}
>> +
>> +	ret = devm_gpio_request(&client->dev, priv->reset_pin, "reset_pin");
>> +	if (ret < 0) {
>> +		dev_err(&client->dev, "request gpio pin %d failed\n",
>> +				priv->reset_pin);
>> +		return ret;
>> +	}
> Please use the gpiod API with the devm_gpiod_get_index_optional() function, it
> will simply your code and take care about GPIO polarity automatically. Don't
> forget to specify the default state using the GPIOD_* flags.

Thank, I will use it.
It seems in this case, use devm_gpiod_get_optional() is enough.

Best Regards,
Josh Wu
>
>> +
>> +	/* Initialize the soc_camera_subdev_desc */
>> +	priv->ssdd_dt.power = ov2640_hw_power;
>> +	priv->ssdd_dt.reset = ov2640_hw_reset;
>> +	client->dev.platform_data = &priv->ssdd_dt;
>> +
>> +	return 0;
>> +}
>> +
>>   /*
>>    * i2c_driver functions
>>    */
>> @@ -1058,12 +1128,6 @@ static int ov2640_probe(struct i2c_client *client,
>>   	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);
>>   	int			ret;
>>
>> -	if (!ssdd) {
>> -		dev_err(&adapter->dev,
>> -			"OV2640: Missing platform_data for driver\n");
>> -		return -EINVAL;
>> -	}
>> -
>>   	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)) {
>>   		dev_err(&adapter->dev,
>>   			"OV2640: I2C-Adapter doesn't support SMBUS\n");
>> @@ -1077,6 +1141,18 @@ static int ov2640_probe(struct i2c_client *client,
>>   		return -ENOMEM;
>>   	}
>>
>> +	if (!ssdd) {
>> +		if (client->dev.of_node) {
>> +			ret = ov2640_probe_dt(client, priv);
>> +			if (ret)
>> +				return ret;
>> +		} else {
>> +			dev_err(&client->dev,
>> +				"Missing platform_data for driver\n");
>> +			return  -EINVAL;
>> +		}
>> +	}
>> +
>>   	v4l2_i2c_subdev_init(&priv->subdev, client, &ov2640_subdev_ops);
>>   	v4l2_ctrl_handler_init(&priv->hdl, 2);
>>   	v4l2_ctrl_new_std(&priv->hdl, &ov2640_ctrl_ops,
>> @@ -1123,9 +1199,16 @@ static const struct i2c_device_id ov2640_id[] = {
>>   };
>>   MODULE_DEVICE_TABLE(i2c, ov2640_id);
>>
>> +static const struct of_device_id ov2640_of_match[] = {
>> +	{.compatible = "omnivision,ov2640", },
>> +	{},
>> +};
>> +MODULE_DEVICE_TABLE(of, ov2640_of_match);
>> +
>>   static struct i2c_driver ov2640_i2c_driver = {
>>   	.driver = {
>>   		.name = "ov2640",
>> +		.of_match_table = of_match_ptr(ov2640_of_match),
>>   	},
>>   	.probe    = ov2640_probe,
>>   	.remove   = ov2640_remove,