Date:   Thu, 5 Mar 2020 22:09:16 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Luca Weiss <luca@...tu.xyz>, linux-leds@...r.kernel.org
Cc:     ~postmarketos/upstreaming@...ts.sr.ht, Pavel Machek <pavel@....cz>,
        Dan Murphy <dmurphy@...com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] leds: add sgm3140 driver

Hi Luca,

Thank you for the patch.

On 2/27/20 7:50 PM, Luca Weiss wrote:
> Add a driver for the SGMICRO SGM3140 Buck/Boost Charge Pump LED driver.
> 
> This device is controller by two GPIO lines, one for enabling the LED
> and the second one for switching between torch and flash mode.
> 
> The device will automatically switch to torch mode after being in flash
> mode for about 250-300ms, so after that time the driver will turn the
> LED off again automatically.
> 
> Signed-off-by: Luca Weiss <luca@...tu.xyz>
> ---
> Hi, this driver is controllable via sysfs and v4l2 APIs (as documented
> in Documentation/leds/leds-class-flash.rst).
> 
> The following is possible:
> 
> # Torch on
> echo 1 > /sys/class/leds/white\:flash/brightness
> # Torch off
> echo 0 > /sys/class/leds/white\:flash/brightness
> # Activate flash
> echo 1 > /sys/class/leds/white\:flash/flash_strobe
> 
> # Torch on
> v4l2-ctl -d /dev/video1 -c led_mode=2
> # Torch off
> v4l2-ctl -d /dev/video1 -c led_mode=0
> # Activate flash
> v4l2-ctl -d /dev/video1 -c strobe=1

What is /dev/video1 ? Did you register vl42 flash subdev
in some v4l2 media controller device?

> 
> Unfortunately the last command (enabling the 'flash' via v4l2 results in
> the following being printed and nothing happening:
> 
>   VIDIOC_S_EXT_CTRLS: failed: Resource busy
>   strobe: Resource busy
> 
> Unfortunately I couldn't figure out the reason so I'm hoping to get some
> guidance for this. iirc it worked at some point but then stopped.

You have to be in flash mode to strobe i.e. led_mode=1.

> I will also write dt bindings for the driver once I have "strobe"
> working.
> 
> Regards,
> Luca
> 
>  drivers/leds/Kconfig        |   9 ++
>  drivers/leds/Makefile       |   1 +
>  drivers/leds/leds-sgm3140.c | 210 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 220 insertions(+)
>  create mode 100644 drivers/leds/leds-sgm3140.c
> 
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 4b68520ac251..7c391af8b380 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -836,6 +836,15 @@ config LEDS_LM36274
>  	  Say Y to enable the LM36274 LED driver for TI LMU devices.
>  	  This supports the LED device LM36274.
>  
> +config LEDS_SGM3140
> +	tristate "LED support for the SGM3140"
> +	depends on LEDS_CLASS_FLASH
> +	depends on V4L2_FLASH_LED_CLASS || !V4L2_FLASH_LED_CLASS
> +	depends on OF
> +	help
> +	  This option enables support for the SGM3140 500mA Buck/Boost Charge
> +	  Pump LED Driver. It has supports flash and torch mode.
> +
>  comment "LED Triggers"
>  source "drivers/leds/trigger/Kconfig"
>  
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index 2da39e896ce8..38d57dd53e4b 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -85,6 +85,7 @@ obj-$(CONFIG_LEDS_LM3601X)		+= leds-lm3601x.o
>  obj-$(CONFIG_LEDS_TI_LMU_COMMON)	+= leds-ti-lmu-common.o
>  obj-$(CONFIG_LEDS_LM3697)		+= leds-lm3697.o
>  obj-$(CONFIG_LEDS_LM36274)		+= leds-lm36274.o
> +obj-$(CONFIG_LEDS_SGM3140)		+= leds-sgm3140.o
>  
>  # LED SPI Drivers
>  obj-$(CONFIG_LEDS_CR0014114)		+= leds-cr0014114.o
> diff --git a/drivers/leds/leds-sgm3140.c b/drivers/leds/leds-sgm3140.c
> new file mode 100644
> index 000000000000..9e91392f0343
> --- /dev/null
> +++ b/drivers/leds/leds-sgm3140.c
> @@ -0,0 +1,210 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2020 Luca Weiss <luca@...tu.xyz>
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/led-class-flash.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +#include <media/v4l2-flash-led-class.h>
> +
> +#define SGM3140_NAME "sgm3140"
> +
> +struct sgm3140 {
> +	struct gpio_desc *flash_gpio;
> +	struct gpio_desc *enable_gpio;
> +
> +	struct led_classdev_flash fled_cdev;
> +	struct v4l2_flash *v4l2_flash;
> +
> +	struct timer_list powerdown_timer;
> +};
> +
> +static struct sgm3140 *flcdev_to_sgm3140(struct led_classdev_flash *flcdev)
> +{
> +	return container_of(flcdev, struct sgm3140, fled_cdev);
> +}
> +
> +int sgm3140_strobe_set(struct led_classdev_flash *fled_cdev, bool state)
> +{
> +	struct sgm3140 *priv = flcdev_to_sgm3140(fled_cdev);
> +
> +	if (state) {
> +		gpiod_set_value_cansleep(priv->flash_gpio, 1);
> +		gpiod_set_value_cansleep(priv->enable_gpio, 1);
> +		mod_timer(&priv->powerdown_timer,
> +			  jiffies + msecs_to_jiffies(250));
> +	} else {
> +		gpiod_set_value_cansleep(priv->enable_gpio, 0);
> +		gpiod_set_value_cansleep(priv->flash_gpio, 0);
> +		del_timer_sync(&priv->powerdown_timer);
> +	}
> +
> +	return 0;
> +}
> +
> +struct led_flash_ops sgm3140_flash_ops = {
> +	.strobe_set = sgm3140_strobe_set,
> +};
> +
> +int sgm3140_brightness_set(struct led_classdev *led_cdev,
> +			   enum led_brightness brightness)
> +{
> +	struct led_classdev_flash *fled_cdev = lcdev_to_flcdev(led_cdev);
> +	struct sgm3140 *priv = flcdev_to_sgm3140(fled_cdev);
> +
> +	if (brightness == LED_OFF)
> +		gpiod_set_value_cansleep(priv->enable_gpio, 0);
> +	else
> +		gpiod_set_value_cansleep(priv->enable_gpio, 1);
> +
> +	return 0;
> +}
> +
> +static void sgm3140_powerdown_timer(struct timer_list *t)
> +{
> +	struct sgm3140 *priv = from_timer(priv, t, powerdown_timer);
> +
> +	gpiod_set_value_cansleep(priv->enable_gpio, 0);
> +	gpiod_set_value_cansleep(priv->flash_gpio, 0);

You could also implement strobe_get op and return from it a flag
indicating if LED is strobing.

> +}
> +
> +#if IS_ENABLED(CONFIG_V4L2_FLASH_LED_CLASS)
> +static void sgm3140_init_v4l2_flash_config(struct sgm3140 *priv,
> +					   struct v4l2_flash_config *v4l2_sd_cfg)
> +{
> +	struct led_classdev *led_cdev = &priv->fled_cdev.led_cdev;
> +	struct led_flash_setting *s;
> +
> +	strlcpy(v4l2_sd_cfg->dev_name, led_cdev->dev->kobj.name,
> +		sizeof(v4l2_sd_cfg->dev_name));
> +
> +	s = &v4l2_sd_cfg->intensity;
> +	s->min = 0;
> +	s->max = 1;
> +	s->step = 1;
> +	s->val = 1;
> +}
> +
> +#else
> +static void sgm3140_init_v4l2_flash_config(struct sgm3140 *priv,
> +					   struct v4l2_flash_config *v4l2_sd_cfg)
> +{
> +}
> +#endif
> +
> +static int sgm3140_probe(struct platform_device *pdev)
> +{
> +	struct sgm3140 *priv;
> +	struct led_classdev *led_cdev;
> +	struct led_classdev_flash *fled_cdev;
> +	struct led_init_data init_data = {};
> +	struct device_node *child_node;
> +	struct v4l2_flash_config v4l2_sd_cfg;

s/v4l2_sd_cfg;/v4l2_sd_cfg = {};/

Otherwise it is possible that some controls would be initialized
to random values.

> +	int ret;
> +
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->flash_gpio = devm_gpiod_get(&pdev->dev, "flash", GPIOD_OUT_LOW);
> +	ret = PTR_ERR_OR_ZERO(priv->flash_gpio);
> +	if (ret) {
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "Failed to request flash gpio: %d\n",
> +				ret);
> +		return ret;
> +	}
> +
> +	priv->enable_gpio = devm_gpiod_get(&pdev->dev, "enable", GPIOD_OUT_LOW);
> +	ret = PTR_ERR_OR_ZERO(priv->enable_gpio);
> +	if (ret) {
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "Failed to request enable gpio: %d\n",
> +				ret);
> +		return ret;
> +	}
> +
> +	child_node = of_get_next_available_child(pdev->dev.of_node, NULL);
> +	if (!child_node) {
> +		dev_err(&pdev->dev, "No DT child node found for connected LED.\n");
> +		return -EINVAL;
> +	}
> +
> +	timer_setup(&priv->powerdown_timer, sgm3140_powerdown_timer, 0);
> +
> +	fled_cdev = &priv->fled_cdev;
> +	led_cdev = &fled_cdev->led_cdev;
> +
> +	fled_cdev->ops = &sgm3140_flash_ops;
> +
> +	led_cdev->brightness_set_blocking = sgm3140_brightness_set;
> +	led_cdev->max_brightness = LED_ON;
> +	led_cdev->flags |= LED_DEV_CAP_FLASH;
> +
> +	init_data.fwnode = of_fwnode_handle(child_node);
> +	init_data.devicename = SGM3140_NAME;

devicename should be skipped in new drivers.

> +
> +	platform_set_drvdata(pdev, priv);
> +
> +	/* Register in the LED subsystem */
> +	ret = led_classdev_flash_register_ext(&pdev->dev, fled_cdev, &init_data);

We already have devm_* prefixed version thereof.

> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "Failed to register flash device: %d\n",
> +			ret);
> +		goto err_flash_register;
> +	}
> +
> +	sgm3140_init_v4l2_flash_config(priv, &v4l2_sd_cfg);
> +
> +	/* Create V4L2 Flash subdev */
> +	priv->v4l2_flash = v4l2_flash_init(&pdev->dev, of_fwnode_handle(child_node),
> +					   fled_cdev, NULL,
> +					   &v4l2_sd_cfg);
> +	if (IS_ERR(priv->v4l2_flash)) {
> +		ret = PTR_ERR(priv->v4l2_flash);
> +		goto err_v4l2_flash_init;
> +	}
> +
> +	return 0;
> +
> +err_v4l2_flash_init:
> +	led_classdev_flash_unregister(fled_cdev);
> +err_flash_register:
> +	of_node_put(child_node);

You need to relase of_node also in case of success.

> +	return ret;
> +}
> +
> +static int sgm3140_remove(struct platform_device *pdev)
> +{
> +	struct sgm3140 *priv = platform_get_drvdata(pdev);
> +
> +	del_timer_sync(&priv->powerdown_timer);
> +
> +	v4l2_flash_release(priv->v4l2_flash);
> +	led_classdev_flash_unregister(&priv->fled_cdev);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id sgm3140_dt_match[] = {
> +	{ .compatible = "sgmicro,sgm3140" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, sgm3140_dt_match);
> +
> +static struct platform_driver sgm3140_driver = {
> +	.probe	= sgm3140_probe,
> +	.remove	= sgm3140_remove,
> +	.driver	= {
> +		.name	= "sgm3140",
> +		.of_match_table = sgm3140_dt_match,
> +	},
> +};
> +
> +module_platform_driver(sgm3140_driver);
> +
> +MODULE_AUTHOR("Luca Weiss <luca@...tu.xyz>");
> +MODULE_DESCRIPTION("SG Micro SGM3140 charge pump led driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 
Best regards,
Jacek Anaszewski

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