From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: jacopo mondi <jacopo@jmondi.org>
Cc: Jacopo Mondi <jacopo+renesas@jmondi.org>, magnus.damm@gmail.com,
        geert@glider.be, mchehab@kernel.org, hverkuil@xs4all.nl,
        robh+dt@kernel.org, mark.rutland@arm.com,
        linux-renesas-soc@vger.kernel.org, linux-media@vger.kernel.org,
        linux-sh@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 7/9] media: i2c: ov772x: Remove soc_camera dependencies
Date: Wed, 03 Jan 2018 17:49:55 +0200
Message-ID: <2597640.1dqQloDucb@avalon>
Organization: Ideas on Board Oy
In-Reply-To: <20180103154458.GD9493@w540>
References: <1514469681-15602-1-git-send-email-jacopo+renesas@jmondi.org> <5703631.yJ335LfYLI@avalon> <20180103154458.GD9493@w540>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
Sender: linux-kernel-owner@vger.kernel.org

Hi Jacopo,

On Wednesday, 3 January 2018 17:44:58 EET jacopo mondi wrote:
> On Tue, Jan 02, 2018 at 05:44:03PM +0200, Laurent Pinchart wrote:
> > On Thursday, 28 December 2017 16:01:19 EET Jacopo Mondi wrote:
> >> Remove soc_camera framework dependencies from ov772x sensor driver.
> >> - Handle clock and gpios
> >> - Register async subdevice
> >> - Remove soc_camera specific g/s_mbus_config operations
> >> - Change image format colorspace to SRGB
> > 
> > Could you explain the rationale for this ?
> 
> Hans suggested this, and I assume it is beacause COLORSPACE_JPEG ==
> (COLORSPACE_SRGB + assumptions on quantization ranges) which does not
> apply to the sensor.

Could you capture it in the commit message ? :-)

> >> - Remove sizes crop from get_selection as driver can't scale
> >> - Add kernel doc to driver interface header file
> >> - Adjust build system
> > 
> > That's a lot for a single patch. On the other hand I don't think splitting
> > this in 7 patches would be a good idea either. If you can find a better
> > granularity, go for it, otherwise keep it as-is. Same comment for the
> > tw9910 driver.
> 
> I know.
> I would have kept changes down to the minimum required to remove
> soc_camera dependencies, but I received comments on other parts of the
> driver not directly soc_camera specific. I understand this, since I'm
> touching the driver it is maybe worth changing some parts of it that
> needs updates..
> 
> >> This commit does not remove the original soc_camera based driver as long
> >> as other platforms depends on soc_camera-based CEU driver.
> >> 
> >> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> >> ---
> >> 
> >>  drivers/media/i2c/Kconfig  |  11 +++
> >>  drivers/media/i2c/Makefile |   1 +
> >>  drivers/media/i2c/ov772x.c | 169 +++++++++++++++++++++++++-------------
> >>  include/media/i2c/ov772x.h |   8 ++-
> >>  4 files changed, 130 insertions(+), 59 deletions(-)
> >> 
> >> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
> >> index cb5d7ff..a61d7f4 100644
> >> --- a/drivers/media/i2c/Kconfig
> >> +++ b/drivers/media/i2c/Kconfig
> > 
> > [snip]
> > 
> >> diff --git a/drivers/media/i2c/ov772x.c b/drivers/media/i2c/ov772x.c
> >> index 8063835..f7b293f 100644
> >> --- a/drivers/media/i2c/ov772x.c
> >> +++ b/drivers/media/i2c/ov772x.c
> >> @@ -1,6 +1,9 @@
> > 
> > [snip]
> > 
> >> @@ -25,8 +26,8 @@
> >> 
> >>  #include <linux/videodev2.h>
> >>  
> >>  #include <media/i2c/ov772x.h>
> > > 
> > > -#include <media/soc_camera.h>
> > > -#include <media/v4l2-clk.h>
> > > +
> > > +#include <media/v4l2-device.h>
> > > 
> > >  #include <media/v4l2-ctrls.h>
> > 
> > I think C comes before D.
> > 
> > >  #include <media/v4l2-subdev.h>
> > >  #include <media/v4l2-image-sizes.h>
> > 
> > [snip]
> > 
> >> @@ -650,13 +653,63 @@ static int ov772x_s_register(struct v4l2_subdev
> >> *sd,
> >>  }
> >>  #endif
> >> 
> >> +static int ov772x_power_on(struct ov772x_priv *priv)
> >> +{
> >> +	struct i2c_client *client = v4l2_get_subdevdata(&priv->subdev);
> >> +	int ret;
> >> +
> >> +	if (priv->info->xclk_rate)
> >> +		ret = clk_set_rate(priv->clk, priv->info->xclk_rate);
> > 
> > The return value is then ignored.
> > 
> > I wonder whether the clk_set_rate() call shouldn't be kept in board code
> > as it's a board-specific frequency. DT platforms would use the
> > assigned-clock-rates property that doesn't require any explicit handling
> > in the driver.
> 
> DT based platforms won't have any info->xlkc_rate, so they should be
> fine. I wonder how could I set rate in board code, as I'm just
> registering an alias for the clock there...

Exactly as done by the current code, get the clock and set the rate :) You can 
do that at initialization time, when you register the alias. Don't forget to 
put the clock too.

> >> +	if (priv->clk) {
> >> +		ret = clk_prepare_enable(priv->clk);
> >> +		if (ret)
> >> +			return ret;
> >> +	}
> >> +
> >> +	if (priv->pwdn_gpio) {
> >> +		gpiod_set_value(priv->pwdn_gpio, 1);
> >> +		usleep_range(500, 1000);
> >> +	}
> >> +
> >> +	/* Reset GPIOs are shared in some platforms. */
> > 
> > I'd make this a FIXME comment as this is really a hack.
> > 
> > 	/*
> > 	 * FIXME: The reset signal is connected to a shared GPIO on some
> > 	 * platforms (namely the SuperH Migo-R). Until a framework becomes
> > 	 * available to handle this cleanly, request the GPIO temporarily
> > 	 * only to avoid conflicts.
> > 	 */
> > 
> > Same for the tw9910 driver.
> 
> Ack.

-- 
Regards,

Laurent Pinchart