linux-kernel - Re: [Patch v4 6/8] media: i2c: ov2659: Add powerdown/reset gpio handling

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Date:   Mon, 30 Sep 2019 10:28:57 +0300
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Benoit Parrot <bparrot@...com>
Cc:     Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v4 6/8] media: i2c: ov2659: Add powerdown/reset gpio
 handling

Hi Benoit,

On Fri, Sep 27, 2019 at 01:47:20PM -0500, Benoit Parrot wrote:
> On some board it is possible that the sensor 'powerdown' and or 'reset'
> pin might be controlled by gpio instead of being tied.
> 
> To implement we add pm_runtime support which will handle the power
> up/down sequence when it is available otherwise the sensor will be
> powered on at module insertion/probe and powered off at module removal.
> 
> Now originally the driver assumed that the sensor would always stay
> powered and keep its register setting. We cannot assume this anymore, so
> every time we "power up" we need to re-program the initial registers
> configuration first. This was previously done only at probe time.
> 
> Signed-off-by: Benoit Parrot <bparrot@...com>
> ---
>  drivers/media/i2c/Kconfig  |  2 +-
>  drivers/media/i2c/ov2659.c | 88 +++++++++++++++++++++++++++++++++++++-
>  2 files changed, 87 insertions(+), 3 deletions(-)
> 
> 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 cd4625432264..7d0baa386644 100644
> --- a/drivers/media/i2c/ov2659.c
> +++ b/drivers/media/i2c/ov2659.c
> @@ -22,9 +22,11 @@
>  
>  #include <linux/clk.h>
>  #include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/i2c.h>
>  #include <linux/module.h>
>  #include <linux/of_graph.h>
> +#include <linux/pm_runtime.h>
>  
>  #include <media/i2c/ov2659.h>
>  #include <media/v4l2-ctrls.h>
> @@ -218,6 +220,11 @@ struct ov2659 {
>  	struct sensor_register *format_ctrl_regs;
>  	struct ov2659_pll_ctrl pll;
>  	int streaming;
> +	/* used to control the sensor PWDN pin */
> +	struct gpio_desc *pwdn_gpio;
> +	/* used to control the sensor RESETB pin */
> +	struct gpio_desc *resetb_gpio;
> +	int on;

Please use runtime PM for this instead. It's hard to get this right
otherwise.

Access to "on" is not serialised with the power state changes. In this case
e.g. drivers/media/i2c/ov5670.c is a good example. I think I'll see how I
could improve smiapp as well.

-- 
Sakari Ailus
sakari.ailus@...ux.intel.com