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Date:   Sun, 18 Apr 2021 17:01:33 +0200
From:   Jacopo Mondi <jacopo@jmondi.org>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Jacopo Mondi <jacopo+renesas@jmondi.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Magnus Damm <magnus.damm@gmail.com>,
        Kieran Bingham <kieran.bingham@ideasonboard.com>,
        Rob Herring <robh+dt@kernel.org>,
        linux-renesas-soc@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 3/7] media: i2c: max9286: Use "maxim,gpio-poc" property
Message-ID: <20210418150133.cql5qnnqj4p4fu6c@uno.localdomain>
References: <20210415122602.87697-1-jacopo+renesas@jmondi.org>
 <20210415122602.87697-4-jacopo+renesas@jmondi.org>
 <YHiRwr+2PzJmoTaQ@pendragon.ideasonboard.com>
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In-Reply-To: <YHiRwr+2PzJmoTaQ@pendragon.ideasonboard.com>
Precedence: bulk

Hi Laurent,

On Thu, Apr 15, 2021 at 10:19:30PM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On Thu, Apr 15, 2021 at 02:25:58PM +0200, Jacopo Mondi wrote:
> > The 'maxim,gpio-poc' property is used when the remote camera
> > power-over-coax is controlled by one of the MAX9286 gpio lines,
> > to instruct the driver about which line to use and what the line
> > polarity is.
> >
> > Add to the max9286 driver support for parsing the newly introduced
> > property and use it if available in place of the usual supply, as it is
> > not possible to establish one as consumer of the max9286 gpio
> > controller.
> >
> > If the new property is present, no gpio controller is registered and
> > 'poc-supply' is ignored.
> >
> > In order to maximize code re-use, break out the max9286 gpio handling
> > function so that they can be used by the gpio controller through the
> > gpio-consumer API, or directly by the driver code.
> >
> > Wrap the power up and power down routines to their own function to
> > be able to use either the gpio line directly or the supply. This will
> > make it easier to control the remote camera power at run time.
> >
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> > ---
> >  drivers/media/i2c/max9286.c | 119 ++++++++++++++++++++++++++++--------
> >  1 file changed, 93 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> > index 6fd4d59fcc72..a8b37783d2ef 100644
> > --- a/drivers/media/i2c/max9286.c
> > +++ b/drivers/media/i2c/max9286.c
> > @@ -15,6 +15,7 @@
> >  #include <linux/fwnode.h>
> >  #include <linux/gpio/consumer.h>
> >  #include <linux/gpio/driver.h>
> > +#include <linux/gpio/machine.h>
> >  #include <linux/i2c.h>
> >  #include <linux/i2c-mux.h>
> >  #include <linux/module.h>
> > @@ -165,6 +166,9 @@ struct max9286_priv {
> >
> >  	u32 reverse_channel_mv;
> >
> > +	u32 gpio_poc;
> > +	u32 gpio_poc_flags;
> > +
> >  	struct v4l2_ctrl_handler ctrls;
> >  	struct v4l2_ctrl *pixelrate;
> >
> > @@ -1022,8 +1026,19 @@ static int max9286_setup(struct max9286_priv *priv)
> >  	return 0;
> >  }
> >
> > -static void max9286_gpio_set(struct gpio_chip *chip,
> > -			     unsigned int offset, int value)
> > +static int max9286_gpio_set(struct max9286_priv *priv, unsigned int offset,
> > +			    int value)
> > +{
> > +	int ret = max9286_read(priv, 0x0f);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	ret = value ? (ret & 0x3) | BIT(offset) : (ret & 0x3) & ~BIT(offset);
> > +	return max9286_write(priv, 0x0f, MAX9286_0X0F_RESERVED | ret);
> > +}
>
> Was there anything wrong with v3, sharing the implementation between the

Yes, my understanding that your comment about not mixing the two
cases as they're mutually exclusive  :)

I found that it actually made sense, as my reasoning was to support
both at the same time, but it was actually not possible. I then
thought it was a good idea to keep them separate....

> gpio-controller and non gpio-controller cases ? In particular, caching
> the state locally seems better, max9286_read() goes over I2C and is thus
> slow.

At the expense of an additional i2c read... The gpio is only toggled
at power-up/down, so I considered this acceptable...

Both solutions are ok with me, I can restore the usage of gpio->state
or keep what I have here...

The only argument in favour of using gpio->state is that it paves the
way for the usage of 'gpio-poc' and for registering a gpio-controller
on the other gpio line at the same time, in future.. I think I'll
switch back to that solution then...

Thanks
  j
>
> > +
> > +static void max9286_gpiochip_set(struct gpio_chip *chip,
> > +				 unsigned int offset, int value)
> >  {
> >  	struct max9286_priv *priv = gpiochip_get_data(chip);
> >
> > @@ -1035,7 +1050,7 @@ static void max9286_gpio_set(struct gpio_chip *chip,
> >  	max9286_write(priv, 0x0f, MAX9286_0X0F_RESERVED | priv->gpio_state);
> >  }
> >
> > -static int max9286_gpio_get(struct gpio_chip *chip, unsigned int offset)
> > +static int max9286_gpiochip_get(struct gpio_chip *chip, unsigned int offset)
> >  {
> >  	struct max9286_priv *priv = gpiochip_get_data(chip);
> >
> > @@ -1055,8 +1070,8 @@ static int max9286_register_gpio(struct max9286_priv *priv)
> >  	gpio->of_node = dev->of_node;
> >  	gpio->ngpio = 2;
> >  	gpio->base = -1;
> > -	gpio->set = max9286_gpio_set;
> > -	gpio->get = max9286_gpio_get;
> > +	gpio->set = max9286_gpiochip_set;
> > +	gpio->get = max9286_gpiochip_get;
> >  	gpio->can_sleep = true;
> >
> >  	/* GPIO values default to high */
> > @@ -1069,6 +1084,71 @@ static int max9286_register_gpio(struct max9286_priv *priv)
> >  	return ret;
> >  }
> >
> > +static int max9286_parse_gpios(struct max9286_priv *priv)
> > +{
> > +	struct device *dev = &priv->client->dev;
> > +	u32 gpio_poc[2];
> > +	int ret;
> > +
> > +	/*
> > +	 * Parse the "gpio-poc" vendor property. If the camera power is
> > +	 * controlled by one of the MAX9286 gpio lines, do not register
> > +	 * the gpio controller and ignore 'poc-supply'.
> > +	 */
> > +	ret = of_property_read_u32_array(dev->of_node,
> > +					 "maxim,gpio-poc", gpio_poc, 2);
> > +	if (!ret) {
> > +		priv->gpio_poc = gpio_poc[0];
> > +		priv->gpio_poc_flags = gpio_poc[1];
> > +		if (priv->gpio_poc > 1 ||
> > +		    (priv->gpio_poc_flags != GPIO_ACTIVE_HIGH &&
> > +		     priv->gpio_poc_flags != GPIO_ACTIVE_LOW)) {
> > +			dev_err(dev, "Invalid 'gpio-poc': (%u %u)\n",
> > +				priv->gpio_poc, priv->gpio_poc_flags);
> > +			return -EINVAL;
> > +		}
> > +
> > +		return 0;
> > +	}
> > +
> > +	ret = max9286_register_gpio(priv);
> > +	if (ret)
> > +		return ret;
> > +
> > +	priv->regulator = devm_regulator_get(dev, "poc");
> > +	if (IS_ERR(priv->regulator)) {
> > +		if (PTR_ERR(priv->regulator) != -EPROBE_DEFER)
> > +			dev_err(dev, "Unable to get PoC regulator (%ld)\n",
> > +				PTR_ERR(priv->regulator));
> > +		return PTR_ERR(priv->regulator);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int max9286_poc_enable(struct max9286_priv *priv, bool enable)
> > +{
> > +	int ret;
> > +
> > +	/* If "poc-gpio" is used, toggle the line and do not use regulator. */
> > +	if (enable)
> > +		ret = priv->regulator
> > +		    ? regulator_enable(priv->regulator)
> > +		    : max9286_gpio_set(priv, priv->gpio_poc,
> > +				       enable ^ priv->gpio_poc_flags);
> > +	else
> > +		ret = priv->regulator
> > +		    ? regulator_disable(priv->regulator)
> > +		    : max9286_gpio_set(priv, priv->gpio_poc,
> > +				       enable ^ priv->gpio_poc_flags);
> > +
> > +	if (ret < 0)
> > +		dev_err(&priv->client->dev, "Unable to turn PoC %s\n",
> > +			enable ? "on" : "off");
> > +
> > +	return ret;
> > +}
> > +
> >  static int max9286_init(struct device *dev)
> >  {
> >  	struct max9286_priv *priv;
> > @@ -1078,17 +1158,14 @@ static int max9286_init(struct device *dev)
> >  	client = to_i2c_client(dev);
> >  	priv = i2c_get_clientdata(client);
> >
> > -	/* Enable the bus power. */
> > -	ret = regulator_enable(priv->regulator);
> > -	if (ret < 0) {
> > -		dev_err(&client->dev, "Unable to turn PoC on\n");
> > +	ret = max9286_poc_enable(priv, true);
> > +	if (ret)
> >  		return ret;
> > -	}
> >
> >  	ret = max9286_setup(priv);
> >  	if (ret) {
> >  		dev_err(dev, "Unable to setup max9286\n");
> > -		goto err_regulator;
> > +		goto err_poc_disable;
> >  	}
> >
> >  	/*
> > @@ -1098,7 +1175,7 @@ static int max9286_init(struct device *dev)
> >  	ret = max9286_v4l2_register(priv);
> >  	if (ret) {
> >  		dev_err(dev, "Failed to register with V4L2\n");
> > -		goto err_regulator;
> > +		goto err_poc_disable;
> >  	}
> >
> >  	ret = max9286_i2c_mux_init(priv);
> > @@ -1114,8 +1191,8 @@ static int max9286_init(struct device *dev)
> >
> >  err_v4l2_register:
> >  	max9286_v4l2_unregister(priv);
> > -err_regulator:
> > -	regulator_disable(priv->regulator);
> > +err_poc_disable:
> > +	max9286_poc_enable(priv, false);
> >
> >  	return ret;
> >  }
> > @@ -1286,20 +1363,10 @@ static int max9286_probe(struct i2c_client *client)
> >  	 */
> >  	max9286_configure_i2c(priv, false);
> >
> > -	ret = max9286_register_gpio(priv);
> > +	ret = max9286_parse_gpios(priv);
> >  	if (ret)
> >  		goto err_powerdown;
> >
> > -	priv->regulator = devm_regulator_get(&client->dev, "poc");
> > -	if (IS_ERR(priv->regulator)) {
> > -		if (PTR_ERR(priv->regulator) != -EPROBE_DEFER)
> > -			dev_err(&client->dev,
> > -				"Unable to get PoC regulator (%ld)\n",
> > -				PTR_ERR(priv->regulator));
> > -		ret = PTR_ERR(priv->regulator);
> > -		goto err_powerdown;
> > -	}
> > -
> >  	ret = max9286_parse_dt(priv);
> >  	if (ret)
> >  		goto err_powerdown;
> > @@ -1326,7 +1393,7 @@ static int max9286_remove(struct i2c_client *client)
> >
> >  	max9286_v4l2_unregister(priv);
> >
> > -	regulator_disable(priv->regulator);
> > +	max9286_poc_enable(priv, false);
> >
> >  	gpiod_set_value_cansleep(priv->gpiod_pwdn, 0);
> >
>
> --
> Regards,
>
> Laurent Pinchart