Re: [v2 2/3] media: ov8856: Add devicetree support

From: Sakari Ailus <sakari.ailus@iki.fi>
To: Robert Foss <robert.foss@linaro.org>
Cc: Dongchun Zhu <dongchun.zhu@mediatek.com>,
	Fabio Estevam <festevam@gmail.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Tomasz Figa <tfiga@chromium.org>,
	linux-media@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [v2 2/3] media: ov8856: Add devicetree support
Date: Fri, 13 Mar 2020 14:17:46 +0200	[thread overview]
Message-ID: <20200313121746.GC5730@valkosipuli.retiisi.org.uk> (raw)
In-Reply-To: <20200313110350.10864-3-robert.foss@linaro.org>

Hi Robert,

On Fri, Mar 13, 2020 at 12:03:49PM +0100, Robert Foss wrote:
> Add devicetree match table, and enable ov8856_probe()
> to initialize power, clocks and reset pins.
> 
> Signed-off-by: Robert Foss <robert.foss@linaro.org>
> ---
> 
> - Changes since v1:
>   * Fabio: Change n_shutdown_gpio name to reset_gpio
>   * Fabio: Invert reset_gpio due to GPIO_ACTIVE_HIGH -> GPIO_ACTIVE_LOW change
>   * Fabio: Remove empty line
>   * Fabio: Remove real error from devm_gpiod_get() failures
>   * Andy & Sakari: Make XVCLK optional since to not break ACPI
>   * Sakari: ARRAY_SIZE() directly instead of through OV8856_NUM_SUPPLIES
>   * Sakari: Use XVCLK rate as provided by DT
> 
>  drivers/media/i2c/ov8856.c | 109 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 107 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov8856.c b/drivers/media/i2c/ov8856.c
> index 8655842af275..db61eed223e8 100644
> --- a/drivers/media/i2c/ov8856.c
> +++ b/drivers/media/i2c/ov8856.c
> @@ -3,10 +3,13 @@
>  
>  #include <asm/unaligned.h>
>  #include <linux/acpi.h>
> +#include <linux/clk.h>
>  #include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/i2c.h>
>  #include <linux/module.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/regulator/consumer.h>
>  #include <media/v4l2-ctrls.h>
>  #include <media/v4l2-device.h>
>  #include <media/v4l2-fwnode.h>
> @@ -19,6 +22,8 @@
>  #define OV8856_LINK_FREQ_180MHZ		180000000ULL
>  #define OV8856_SCLK			144000000ULL
>  #define OV8856_MCLK			19200000
> +#define OV8856_XVCLK_19_2		19200000

Please use a single macro to refer to 19,2 MHz clock.

> +#define OV8856_XVCLK_24			24000000

This doesn't seem to be needed 

>  #define OV8856_DATA_LANES		4
>  #define OV8856_RGB_DEPTH		10
>  
> @@ -64,6 +69,12 @@
>  
>  #define to_ov8856(_sd)			container_of(_sd, struct ov8856, sd)
>  
> +static const char * const ov8856_supply_names[] = {
> +	"dovdd",	/* Digital I/O power */
> +	"avdd",		/* Analog power */
> +	"dvdd",		/* Digital core power */
> +};
> +
>  enum {
>  	OV8856_LINK_FREQ_720MBPS,
>  	OV8856_LINK_FREQ_360MBPS,
> @@ -566,6 +577,10 @@ struct ov8856 {
>  	struct media_pad pad;
>  	struct v4l2_ctrl_handler ctrl_handler;
>  
> +	struct clk		*xvclk;
> +	struct gpio_desc	*reset_gpio;
> +	struct regulator_bulk_data supplies[ARRAY_SIZE(ov8856_supply_names)];
> +
>  	/* V4L2 Controls */
>  	struct v4l2_ctrl *link_freq;
>  	struct v4l2_ctrl *pixel_rate;
> @@ -908,6 +923,46 @@ static int ov8856_set_stream(struct v4l2_subdev *sd, int enable)
>  	return ret;
>  }
>  
> +static int __ov8856_power_on(struct ov8856 *ov8856)
> +{
> +	struct i2c_client *client = v4l2_get_subdevdata(&ov8856->sd);
> +	int ret;
> +
> +	ret = clk_prepare_enable(ov8856->xvclk);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to enable xvclk\n");
> +		return ret;
> +	}
> +
> +	gpiod_set_value_cansleep(ov8856->reset_gpio, GPIOD_OUT_HIGH);
> +
> +	ret = regulator_bulk_enable(ARRAY_SIZE(ov8856_supply_names),
> +				    ov8856->supplies);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to enable regulators\n");
> +		goto disable_clk;
> +	}
> +
> +	gpiod_set_value_cansleep(ov8856->reset_gpio, GPIOD_OUT_LOW);
> +
> +	usleep_range(1500, 1800);

I think you could omit the delay on ACPI based systems. Or just bail out
early in that case.

> +
> +	return 0;
> +
> +disable_clk:

How about the GPIO here?

> +	clk_disable_unprepare(ov8856->xvclk);
> +
> +	return ret;
> +}
> +
> +static void __ov8856_power_off(struct ov8856 *ov8856)
> +{
> +	gpiod_set_value_cansleep(ov8856->reset_gpio, GPIOD_OUT_HIGH);
> +	regulator_bulk_disable(ARRAY_SIZE(ov8856_supply_names),
> +			       ov8856->supplies);
> +	clk_disable_unprepare(ov8856->xvclk);
> +}

You'll need to call the two in the driver's suspend and resume functions.

> +
>  static int __maybe_unused ov8856_suspend(struct device *dev)
>  {
>  	struct i2c_client *client = to_i2c_client(dev);
> @@ -1175,7 +1230,7 @@ static int ov8856_remove(struct i2c_client *client)
>  static int ov8856_probe(struct i2c_client *client)
>  {
>  	struct ov8856 *ov8856;
> -	int ret;
> +	int i, ret;

unsigned int?

>  
>  	ret = ov8856_check_hwcfg(&client->dev);
>  	if (ret) {
> @@ -1189,10 +1244,50 @@ static int ov8856_probe(struct i2c_client *client)
>  		return -ENOMEM;
>  
>  	v4l2_i2c_subdev_init(&ov8856->sd, client, &ov8856_subdev_ops);
> +	ov8856->xvclk = devm_clk_get(&client->dev, "xvclk");
> +	if (PTR_ERR(ov8856->xvclk) == -ENOENT) {
> +		dev_info(&client->dev, "xvclk clock not defined, continuing...\n");

How about dev_dbg()?

> +		ov8856->xvclk = NULL;
> +	} else if (IS_ERR(ov8856->xvclk)) {
> +		dev_err(&client->dev, "could not get xvclk clock (%ld)\n",
> +			PTR_ERR(ov8856->xvclk));
> +		return PTR_ERR(ov8856->xvclk);
> +	}
> +
> +	ret = clk_set_rate(ov8856->xvclk, OV8856_XVCLK_24);

This should either come from platform data, or perhaps it'd be even better
to get the clock rate and use assigned-clock-rates. I guess that's
preferred nowadays.

> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to set xvclk rate (24MHz)\n");
> +		return ret;
> +	}
> +
> +	ov8856->reset_gpio = devm_gpiod_get(&client->dev, "reset",
> +					       GPIOD_OUT_HIGH);

Indentation.

What if no gpio is defined?

> +	if (IS_ERR(ov8856->reset_gpio)) {
> +		dev_err(&client->dev, "failed to get reset-gpios\n");
> +		return PTR_ERR(ov8856->reset_gpio);
> +	}
> +
> +	for (i = 0; i < ARRAY_SIZE(ov8856_supply_names); i++)
> +		ov8856->supplies[i].supply = ov8856_supply_names[i];
> +
> +	ret = devm_regulator_bulk_get(&client->dev,
> +				      ARRAY_SIZE(ov8856_supply_names),
> +				      ov8856->supplies);

What happens if there are no regulators?

> +	if (ret) {
> +		dev_warn(&client->dev, "failed to get regulators\n");
> +		return ret;
> +	}
> +
> +	ret = __ov8856_power_on(ov8856);
> +	if (ret) {
> +		dev_warn(&client->dev, "failed to power on\n");
> +		return ret;
> +	}
> +
>  	ret = ov8856_identify_module(ov8856);
>  	if (ret) {
>  		dev_err(&client->dev, "failed to find sensor: %d", ret);
> -		return ret;
> +		goto probe_power_off;
>  	}
>  
>  	mutex_init(&ov8856->mutex);
> @@ -1238,6 +1333,9 @@ static int ov8856_probe(struct i2c_client *client)
>  	v4l2_ctrl_handler_free(ov8856->sd.ctrl_handler);
>  	mutex_destroy(&ov8856->mutex);
>  
> +probe_power_off:
> +	__ov8856_power_off(ov8856);
> +

Also remember to power off the device in remove().

>  	return ret;
>  }
>  
> @@ -1254,11 +1352,18 @@ static const struct acpi_device_id ov8856_acpi_ids[] = {
>  MODULE_DEVICE_TABLE(acpi, ov8856_acpi_ids);
>  #endif
>  
> +static const struct of_device_id ov8856_of_match[] = {
> +	{ .compatible = "ovti,ov8856" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, ov8856_of_match);
> +
>  static struct i2c_driver ov8856_i2c_driver = {
>  	.driver = {
>  		.name = "ov8856",
>  		.pm = &ov8856_pm_ops,
>  		.acpi_match_table = ACPI_PTR(ov8856_acpi_ids),
> +		.of_match_table = ov8856_of_match,
>  	},
>  	.probe_new = ov8856_probe,
>  	.remove = ov8856_remove,

-- 
Regards,

Sakari Ailus