linux-kernel - Re: [PATCH v2 3/3] media: imx258: Get clock from device properties and enable it via runtime PM

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Date:   Mon, 21 Sep 2020 14:02:34 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] media: imx258: Get clock from device properties
 and enable it via runtime PM

On Wed, Sep 02, 2020 at 10:39:35AM +0300, Sakari Ailus wrote:
> Hi Krzysztof,
> 
> Thanks for the update.
> 
> On Wed, Sep 02, 2020 at 09:18:10AM +0200, Krzysztof Kozlowski wrote:
> > The IMX258 sensor driver checked in device properties for a
> > clock-frequency property which actually does not mean that the clock is
> > really running such frequency or is it even enabled.
> > 
> > Get the provided clock and check it frequency.  If none is provided,
> > fall back to old property.
> > 
> > Enable the clock when accessing the IMX258 registers and when streaming
> > starts with runtime PM.
> > 
> > Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
> > 
> > ---
> > 
> > Changes since v1:
> > 1. Use runtime PM for clock toggling
> > ---
> >  drivers/media/i2c/imx258.c | 68 ++++++++++++++++++++++++++++++++++++++++------
> >  1 file changed, 59 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/media/i2c/imx258.c b/drivers/media/i2c/imx258.c
> > index c20bac9b00ec..ee38dafb8450 100644
> > --- a/drivers/media/i2c/imx258.c
> > +++ b/drivers/media/i2c/imx258.c
> > @@ -2,6 +2,7 @@
> >  // Copyright (C) 2018 Intel Corporation
> >  
> >  #include <linux/acpi.h>
> > +#include <linux/clk.h>
> >  #include <linux/delay.h>
> >  #include <linux/i2c.h>
> >  #include <linux/module.h>
> > @@ -68,6 +69,9 @@
> >  #define REG_CONFIG_MIRROR_FLIP		0x03
> >  #define REG_CONFIG_FLIP_TEST_PATTERN	0x02
> >  
> > +/* Input clock frequency in Hz */
> > +#define IMX258_INPUT_CLOCK_FREQ		19200000
> > +
> >  struct imx258_reg {
> >  	u16 address;
> >  	u8 val;
> > @@ -610,6 +614,8 @@ struct imx258 {
> >  
> >  	/* Streaming on/off */
> >  	bool streaming;
> > +
> > +	struct clk *clk;
> >  };
> >  
> >  static inline struct imx258 *to_imx258(struct v4l2_subdev *_sd)
> > @@ -972,6 +978,27 @@ static int imx258_stop_streaming(struct imx258 *imx258)
> >  	return 0;
> >  }
> >  
> > +static int imx258_power_on(struct device *dev)
> > +{
> > +	struct imx258 *imx258 = dev_get_drvdata(dev);
> > +	int ret;
> > +
> > +	ret = clk_prepare_enable(imx258->clk);
> > +	if (ret)
> > +		dev_err(dev, "failed to enable clock\n");
> > +
> > +	return ret;
> > +}
> > +
> > +static int imx258_power_off(struct device *dev)
> > +{
> > +	struct imx258 *imx258 = dev_get_drvdata(dev);
> > +
> > +	clk_disable_unprepare(imx258->clk);
> > +
> > +	return 0;
> > +}
> > +
> >  static int imx258_set_stream(struct v4l2_subdev *sd, int enable)
> >  {
> >  	struct imx258 *imx258 = to_imx258(sd);
> > @@ -1201,9 +1228,27 @@ static int imx258_probe(struct i2c_client *client)
> >  	int ret;
> >  	u32 val = 0;
> >  
> > -	device_property_read_u32(&client->dev, "clock-frequency", &val);
> > -	if (val != 19200000)
> > -		return -EINVAL;
> > +	imx258 = devm_kzalloc(&client->dev, sizeof(*imx258), GFP_KERNEL);
> > +	if (!imx258)
> > +		return -ENOMEM;
> > +
> > +	dev_set_drvdata(&client->dev, imx258);
> 
> This you cannot do --- it'll be overwritten by v4l2_i2c_subdev_init().

Right, thanks.

> 
> > +
> > +	imx258->clk = devm_clk_get_optional(&client->dev, NULL);
> > +	if (!imx258->clk) {
> 
> You can move declaration of val here (I think).

No, the val is used later in further device_property_read* calls.

> 
> > +		dev_info(&client->dev, "no clock provided, using clock-frequency property\n");
> 
> As this is showing up on all ACPI based systems, I guess dev_dbg() would be
> more appropriate.

Sure, I'll make it debug.

> 
> Please also wrap lines over 80 if they reasonably can be.

OK

Thanks for the review.

Best regards,
Krzysztof