linux-kernel - Re: [PATCH v4 3/3] media: ov7670: Add the s

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Date:   Mon, 18 Sep 2017 17:26:16 +0800
From:   "Yang, Wenyou" <Wenyou.Yang@...rochip.com>
To:     Sakari Ailus <sakari.ailus@....fi>
CC:     Jonathan Corbet <corbet@....net>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>
Subject: Re: [PATCH v4 3/3] media: ov7670: Add the s_power operation

Hi Sakari,


On 2017/9/18 15:35, Sakari Ailus wrote:
> Hi Wenyou,
>
> Thanks for the update.
>
> The driver exposes controls that are accessible through the sub-device node
> even if the device hasn't been powered on.
>
> Many ISP and bridge drivers will also power the sensor down once the last
> user of the user space device nodes disappears. You could keep the device
> powered at all times or change the behaviour so that controls can be
> accessed when the power is off.
>
> The best option would be to convert the driver to use runtime PM.
Yes, I agree with you.
I also noticed there are a lot of things needed to improve except for 
it, such as the platform data via device tree.
I would like do it in another patch set. I will continue to work on it.
> An example of this can be found in drivers/media/i2c/ov13858.c .
A good example, thank you for your providing.
>
> On Mon, Sep 18, 2017 at 02:45:14PM +0800, Wenyou Yang wrote:
>> Add the s_power operation which is responsible for manipulating the
>> power dowm mode through the PWDN pin and the reset operation through
>> the RESET pin.
>>
>> Signed-off-by: Wenyou Yang <wenyou.yang@...rochip.com>
>> ---
>>
>> Changes in v4: None
>> Changes in v3: None
>> Changes in v2:
>>   - Add the patch to support the get_fmt ops.
>>   - Remove the redundant invoking ov7670_init_gpio().
>>
>>   drivers/media/i2c/ov7670.c | 32 +++++++++++++++++++++++++++-----
>>   1 file changed, 27 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/media/i2c/ov7670.c b/drivers/media/i2c/ov7670.c
>> index 456f48057605..304abc769a67 100644
>> --- a/drivers/media/i2c/ov7670.c
>> +++ b/drivers/media/i2c/ov7670.c
>> @@ -1542,6 +1542,22 @@ static int ov7670_s_register(struct v4l2_subdev *sd, const struct v4l2_dbg_regis
>>   }
>>   #endif
>>   
>> +static int ov7670_s_power(struct v4l2_subdev *sd, int on)
>> +{
>> +	struct ov7670_info *info = to_state(sd);
>> +
>> +	if (info->pwdn_gpio)
>> +		gpiod_direction_output(info->pwdn_gpio, !on);
>> +	if (on && info->resetb_gpio) {
>> +		gpiod_set_value(info->resetb_gpio, 1);
>> +		usleep_range(500, 1000);
>> +		gpiod_set_value(info->resetb_gpio, 0);
>> +		usleep_range(3000, 5000);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>   static void ov7670_get_default_format(struct v4l2_subdev *sd,
>>   				      struct v4l2_mbus_framefmt *format)
>>   {
>> @@ -1575,6 +1591,7 @@ static const struct v4l2_subdev_core_ops ov7670_core_ops = {
>>   	.g_register = ov7670_g_register,
>>   	.s_register = ov7670_s_register,
>>   #endif
>> +	.s_power = ov7670_s_power,
>>   };
>>   
>>   static const struct v4l2_subdev_video_ops ov7670_video_ops = {
>> @@ -1692,23 +1709,25 @@ static int ov7670_probe(struct i2c_client *client,
>>   	if (ret)
>>   		return ret;
>>   
>> -	ret = ov7670_init_gpio(client, info);
>> -	if (ret)
>> -		goto clk_disable;
>> -
>>   	info->clock_speed = clk_get_rate(info->clk) / 1000000;
>>   	if (info->clock_speed < 10 || info->clock_speed > 48) {
>>   		ret = -EINVAL;
>>   		goto clk_disable;
>>   	}
>>   
>> +	ret = ov7670_init_gpio(client, info);
>> +	if (ret)
>> +		goto clk_disable;
>> +
>> +	ov7670_s_power(sd, 1);
>> +
>>   	/* Make sure it's an ov7670 */
>>   	ret = ov7670_detect(sd);
>>   	if (ret) {
>>   		v4l_dbg(1, debug, client,
>>   			"chip found @ 0x%x (%s) is not an ov7670 chip.\n",
>>   			client->addr << 1, client->adapter->name);
>> -		goto clk_disable;
>> +		goto power_off;
>>   	}
>>   	v4l_info(client, "chip found @ 0x%02x (%s)\n",
>>   			client->addr << 1, client->adapter->name);
>> @@ -1787,6 +1806,8 @@ static int ov7670_probe(struct i2c_client *client,
>>   #endif
>>   hdl_free:
>>   	v4l2_ctrl_handler_free(&info->hdl);
>> +power_off:
>> +	ov7670_s_power(sd, 0);
>>   clk_disable:
>>   	clk_disable_unprepare(info->clk);
>>   	return ret;
>> @@ -1804,6 +1825,7 @@ static int ov7670_remove(struct i2c_client *client)
>>   #if defined(CONFIG_MEDIA_CONTROLLER)
>>   	media_entity_cleanup(&info->sd.entity);
>>   #endif
>> +	ov7670_s_power(sd, 0);
>>   	return 0;
>>   }
>>   
>> -- 
>> 2.13.0
>>

Best Regards,
Wenyou Yang