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From:   "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Date:   Sat, 14 Sep 2019 11:33:42 +0100
Message-ID: <CA+V-a8stmX2WmJEQRvvdOfHiFNgmEbtPTWtn+Fuq2h8SW4N3Hw@mail.gmail.com>
Subject: Re: [Patch 4/6] media: i2c: ov2659: Add optional powerdown gpio handling
To:     Benoit Parrot <bparrot@ti.com>
Cc:     Hans Verkuil <hverkuil@xs4all.nl>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        linux-media <linux-media@vger.kernel.org>,
        devicetree@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Benoit,

On Thu, Sep 12, 2019 at 1:58 PM Benoit Parrot <bparrot@ti.com> wrote:
>
> On some board it is possible that the sensor 'powerdown'
> pin might be controlled with a gpio instead of being
> tied to always powered.
>
> This patch add support to specify an optional gpio
> which will be set at probe time and remained on.
>
> Signed-off-by: Benoit Parrot <bparrot@ti.com>
> ---
>  drivers/media/i2c/Kconfig  |  2 +-
>  drivers/media/i2c/ov2659.c | 13 +++++++++++++
>  2 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
> index 7eee1812bba3..315c1d8bdb7b 100644
> --- a/drivers/media/i2c/Kconfig
> +++ b/drivers/media/i2c/Kconfig
> @@ -634,7 +634,7 @@ config VIDEO_OV2640
>  config VIDEO_OV2659
>         tristate "OmniVision OV2659 sensor support"
>         depends on VIDEO_V4L2 && I2C
> -       depends on MEDIA_CAMERA_SUPPORT
> +       depends on MEDIA_CAMERA_SUPPORT && GPIOLIB
>         select V4L2_FWNODE
>         help
>           This is a Video4Linux2 sensor driver for the OmniVision
> diff --git a/drivers/media/i2c/ov2659.c b/drivers/media/i2c/ov2659.c
> index efbe6dc720e2..c64f73bef336 100644
> --- a/drivers/media/i2c/ov2659.c
> +++ b/drivers/media/i2c/ov2659.c
> @@ -32,6 +32,8 @@
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/of_graph.h>
> +#include <linux/of_gpio.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/slab.h>
>  #include <linux/uaccess.h>
>  #include <linux/videodev2.h>
> @@ -232,6 +234,8 @@ struct ov2659 {
>         struct sensor_register *format_ctrl_regs;
>         struct ov2659_pll_ctrl pll;
>         int streaming;
> +       /* used to control the sensor powerdownN pin */
> +       struct gpio_desc *pwrdn_gpio;
>  };
>
>  static const struct sensor_register ov2659_init_regs[] = {
> @@ -1391,6 +1395,7 @@ static int ov2659_probe(struct i2c_client *client)
>         struct v4l2_subdev *sd;
>         struct ov2659 *ov2659;
>         struct clk *clk;
> +       struct gpio_desc *gpio;

you don't need the local var here you can just assign it directly to pwrdn_gpio.

>         int ret;
>
>         if (!pdata) {
> @@ -1414,6 +1419,14 @@ static int ov2659_probe(struct i2c_client *client)
>             ov2659->xvclk_frequency > 27000000)
>                 return -EINVAL;
>
> +       /* Optional gpio don't fail if not present */
> +       gpio = devm_gpiod_get_optional(&client->dev, "powerdown",
> +                                      GPIOD_OUT_HIGH);
> +       if (IS_ERR(gpio))
> +               return PTR_ERR(gpio);
> +
> +       ov2659->pwrdn_gpio = gpio;
> +
apart from assigning it you don't actually use it.

you will also have to read the reset gpio pin and implement
ov2659_set_power() and
call it in appropriate places/ s_power ?

Cheers,
--Prabhakar Lad