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

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Date:   Mon, 30 Sep 2019 07:29:46 -0500
From:   Benoit Parrot <bparrot@...com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.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

Sakari Ailus <sakari.ailus@...ux.intel.com> wrote on Mon [2019-Sep-30 10:28:57 +0300]:
> 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.

So you mean, I should use the "if (!pm_runtime_get_if_in_use(dev))"
construct?

Ok I'll switch it to that, just using "on" was a little simple but I
already had it :).


> 
> 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.

Ok so that driver uses this pm method but does not actually power up or
down the sensor. 

Benoit

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