Re: [PATCH v4 3/3] media: ov7670: Add the s_power operation

[Yang, Wenyou]

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@xxxxxxxxxxxxx>
> > ---
> >
> > 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