Date:	Thu, 11 Dec 2014 16:16:48 +0200
From:	Sakari Ailus <sakari.ailus@....fi>
To:	Jacek Anaszewski <j.anaszewski@...sung.com>
Cc:	linux-leds@...r.kernel.org, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, kyungmin.park@...sung.com,
	b.zolnierkie@...sung.com, pavel@....cz, cooloney@...il.com,
	rpurdie@...ys.net, s.nawrocki@...sung.com, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org
Subject: Re: [PATCH/RFC v9 08/19] leds: Add driver for AAT1290 current
 regulator

Hi Jacek,

On Wed, Dec 03, 2014 at 05:06:43PM +0100, Jacek Anaszewski wrote:
> This patch adds a driver for the 1.5A Step-Up Current Regulator
> for Flash LEDs. The device is programmed through a Skyworks proprietary
> AS2Cwire serial digital interface.
> 
> Signed-off-by: Jacek Anaszewski <j.anaszewski@...sung.com>
> Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
> Cc: Bryan Wu <cooloney@...il.com>
> Cc: Richard Purdie <rpurdie@...ys.net>
> ---
>  drivers/leds/Kconfig        |    7 +
>  drivers/leds/Makefile       |    1 +
>  drivers/leds/leds-aat1290.c |  413 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 421 insertions(+)
>  create mode 100644 drivers/leds/leds-aat1290.c
> 
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 2e66d55..ec4b78c 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -39,6 +39,13 @@ config LEDS_88PM860X
>  	  This option enables support for on-chip LED drivers found on Marvell
>  	  Semiconductor 88PM8606 PMIC.
>  
> +config LEDS_AAT1290
> +	tristate "LED support for the AAT1290"
> +	depends on LEDS_CLASS_FLASH
> +	depends on OF
> +	help
> +	 This option enables support for the LEDs on the AAT1290.
> +
>  config LEDS_LM3530
>  	tristate "LCD Backlight driver for LM3530"
>  	depends on LEDS_CLASS
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index 57ca62b..b802251 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -7,6 +7,7 @@ obj-$(CONFIG_LEDS_TRIGGERS)		+= led-triggers.o
>  
>  # LED Platform Drivers
>  obj-$(CONFIG_LEDS_88PM860X)		+= leds-88pm860x.o
> +obj-$(CONFIG_LEDS_AAT1290)		+= leds-aat1290.o
>  obj-$(CONFIG_LEDS_BD2802)		+= leds-bd2802.o
>  obj-$(CONFIG_LEDS_LOCOMO)		+= leds-locomo.o
>  obj-$(CONFIG_LEDS_LM3530)		+= leds-lm3530.o
> diff --git a/drivers/leds/leds-aat1290.c b/drivers/leds/leds-aat1290.c
> new file mode 100644
> index 0000000..15d969b
> --- /dev/null
> +++ b/drivers/leds/leds-aat1290.c
> @@ -0,0 +1,413 @@
> +/*
> + *	LED Flash class driver for the AAT1290
> + *	1.5A Step-Up Current Regulator for Flash LEDs
> + *
> + *	Copyright (C) 2014, Samsung Electronics Co., Ltd.
> + *	Author: Jacek Anaszewski <j.anaszewski@...sung.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * version 2 as published by the Free Software Foundation.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/slab.h>
> +#include <linux/platform_device.h>
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/led-class-flash.h>
> +#include <linux/leds.h>
> +#include <linux/mutex.h>
> +#include <linux/gpio.h>
> +#include <linux/of_gpio.h>
> +#include <linux/of.h>
> +#include <linux/workqueue.h>

Alphabetic order, please.

> +
> +#define AAT1290_MOVIE_MODE_CURRENT_ADDR	17
> +#define AAT1290_FLASH_SAFETY_TIMER_ADDR	18
> +#define AAT1290_MOVIE_MODE_CONFIG_ADDR	19
> +#define AAT1290_MM_CURRENT_RATIO_ADDR	20
> +#define AAT1290_LATCH_TIME_US		500
> +#define AAT1290_EN_SET_TICK_TIME_US	1
> +#define AAT1290_MOVIE_MODE_OFF		1
> +#define AAT1290_MOVIE_MODE_ON		3
> +#define AAT1290_MAX_MM_CURR_PERCENT_0	16
> +#define AAT1290_MAX_MM_CURR_PERCENT_100 1
> +#define AAT1290_FLASH_TM_NUM_LEVELS	16

It'd be nice to arrange register bit definitions next to the register
address they're related to. That makes this a lot more readable. Timeouts
separately as well.

Please also align the values on the right to the same column. I think they
mostly are, but at least AAT1290_MAX_MM_CURR_PERCENT_100 uses space instead
of a tab.

> +#define AAT1290_MM_TO_FL_1_92	1
> +#define AAT1290_MM_TO_FL_3_7	2
> +#define AAT1290_MM_TO_FL_5_5	3
> +#define AAT1290_MM_TO_FL_7_3	4
> +#define AAT1290_MM_TO_FL_9	5
> +#define AAT1290_MM_TO_FL_10_7	6
> +#define AAT1290_MM_TO_FL_12_4	7
> +#define AAT1290_MM_TO_FL_14	8
> +#define AAT1290_MM_TO_FL_15_9	9
> +#define AAT1290_MM_TO_FL_17_5	10
> +#define AAT1290_MM_TO_FL_19_1	11
> +#define AAT1290_MM_TO_FL_20_8	12
> +#define AAT1290_MM_TO_FL_22_4	13
> +#define AAT1290_MM_TO_FL_24	14
> +#define AAT1290_MM_TO_FL_25_6	15
> +#define AAT1290_MM_TO_FL_OFF	16
> +
> +struct aat1290_led_settings {
> +	struct led_flash_setting torch_brightness;
> +	struct led_flash_setting flash_brightness;
> +	struct led_flash_setting flash_timeout;
> +};
> +
> +struct aat1290_led {
> +	struct platform_device *pdev;
> +	struct mutex lock;
> +
> +	struct led_classdev_flash ldev;
> +
> +	int flen_gpio;
> +	int en_set_gpio;
> +
> +	u32 max_flash_tm;
> +	bool movie_mode;
> +
> +	char *label;
> +	unsigned int torch_brightness;
> +	unsigned int flash_timeout;
> +	struct work_struct work_brightness_set;
> +};
> +
> +static struct aat1290_led *ldev_to_led(struct led_classdev_flash *ldev)
> +{
> +	return container_of(ldev, struct aat1290_led, ldev);
> +}
> +
> +static void aat1290_as2cwire_write(struct aat1290_led *led, int addr, int value)
> +{
> +	int i;
> +
> +	gpio_set_value(led->flen_gpio, 0);
> +	gpio_set_value(led->en_set_gpio, 0);
> +
> +	udelay(10);

Could you use a #define for this as you are using for the rest?

> +
> +	/* write address */
> +	for (i = 0; i < addr; ++i) {
> +		udelay(AAT1290_EN_SET_TICK_TIME_US);
> +		gpio_set_value(led->en_set_gpio, 0);
> +		udelay(AAT1290_EN_SET_TICK_TIME_US);
> +		gpio_set_value(led->en_set_gpio, 1);
> +	}

This is a very interesting approach to bus implementation. It's a bit like
pulse dial on POTS. :-)

> +
> +	udelay(AAT1290_LATCH_TIME_US);

How precise does this need to be? Could you use usleep_range() instead?

> +
> +	/* write data */
> +	for (i = 0; i < value; ++i) {
> +		udelay(AAT1290_EN_SET_TICK_TIME_US);
> +		gpio_set_value(led->en_set_gpio, 0);
> +		udelay(AAT1290_EN_SET_TICK_TIME_US);
> +		gpio_set_value(led->en_set_gpio, 1);
> +	}
> +
> +	udelay(AAT1290_LATCH_TIME_US);
> +}
> +
> +static void aat1290_set_flash_safety_timer(struct aat1290_led *led,
> +					unsigned int micro_sec)
> +{
> +	struct led_classdev_flash *flash = &led->ldev;
> +	struct led_flash_setting *flash_tm = &flash->timeout;
> +	int flash_tm_reg = AAT1290_FLASH_TM_NUM_LEVELS -
> +				(micro_sec / flash_tm->step) + 1;
> +
> +	aat1290_as2cwire_write(led, AAT1290_FLASH_SAFETY_TIMER_ADDR,
> +							flash_tm_reg);
> +}
> +
> +static void aat1290_brightness_set(struct aat1290_led *led,
> +					enum led_brightness brightness)
> +{
> +	mutex_lock(&led->lock);
> +
> +	if (brightness == 0) {
> +		gpio_set_value(led->flen_gpio, 0);
> +		gpio_set_value(led->en_set_gpio, 0);
> +		goto unlock;
> +	}
> +
> +	if (!led->movie_mode) {
> +		aat1290_as2cwire_write(led, AAT1290_MM_CURRENT_RATIO_ADDR,
> +					AAT1290_MM_TO_FL_1_92);
> +		led->movie_mode = true;
> +	}
> +
> +	aat1290_as2cwire_write(led, AAT1290_MOVIE_MODE_CURRENT_ADDR,
> +				AAT1290_MAX_MM_CURR_PERCENT_0 - brightness);
> +	aat1290_as2cwire_write(led, AAT1290_MOVIE_MODE_CONFIG_ADDR,
> +				AAT1290_MOVIE_MODE_ON);
> +unlock:
> +	mutex_unlock(&led->lock);
> +}
> +
> +/* LED subsystem callbacks */
> +
> +static void aat1290_brightness_set_work(struct work_struct *work)
> +{
> +	struct aat1290_led *led =
> +		container_of(work, struct aat1290_led, work_brightness_set);
> +
> +	aat1290_brightness_set(led, led->torch_brightness);
> +}
> +
> +static void aat1290_led_brightness_set(struct led_classdev *led_cdev,
> +					enum led_brightness brightness)
> +{
> +	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +	struct aat1290_led *led = ldev_to_led(flash);
> +
> +	led->torch_brightness = brightness;
> +	schedule_work(&led->work_brightness_set);

Where is the asynchronous brightness setting used? Don't flash class devices
use always the synchronous variant?

> +}
> +
> +static int aat1290_led_brightness_set_sync(struct led_classdev *led_cdev,
> +					enum led_brightness brightness)
> +{
> +	struct led_classdev_flash *flash = lcdev_to_flash(led_cdev);
> +	struct aat1290_led *led = ldev_to_led(flash);
> +
> +	aat1290_brightness_set(led, brightness);
> +
> +	return 0;
> +}
> +
> +static int aat1290_led_flash_strobe_set(struct led_classdev_flash *flash,
> +					 bool state)
> +
> +{
> +	struct aat1290_led *led = ldev_to_led(flash);
> +	struct led_classdev *led_cdev = &flash->led_cdev;
> +	struct led_flash_setting *timeout = &flash->timeout;
> +
> +	mutex_lock(&led->lock);
> +
> +	if (state == 0) {
> +		gpio_set_value(led->flen_gpio, 0);
> +		gpio_set_value(led->en_set_gpio, 0);
> +		goto unlock;
> +	}
> +
> +	aat1290_set_flash_safety_timer(led, timeout->val);
> +
> +	/*
> +	 * To reenter movie mode after a flash event the part
> +	 * must be cycled off and back on to reset the movie
> +	 * mode and reprogrammed via the AS2Cwire. Therefore
> +	 * the brightness value needs to be updated here to
> +	 * reflect the actual state.
> +	 */
> +	led_cdev->brightness = 0;
> +	led->movie_mode = false;
> +
> +	gpio_set_value(led->flen_gpio, 1);
> +
> +unlock:
> +	mutex_unlock(&led->lock);
> +
> +	return 0;
> +}
> +
> +static int aat1290_led_flash_timeout_set(struct led_classdev_flash *flash,
> +						u32 timeout)
> +{
> +	/*
> +	 * Don't do anything - flash timeout is cached in the led-class-flash
> +	 * core and will be applied in the strobe_set op, as writing the
> +	 * safety timer register spuriously turns the torch mode on.
> +	 */
> +
> +	return 0;
> +}
> +
> +static int aat1290_led_parse_dt(struct aat1290_led *led,
> +				struct device *dev)
> +{
> +	int ret;
> +	char *pname = "label";

You could use two const static variables for this, or a define. No need to
assign the variable in the middle.

I have to admit I've usually just written the string in verbatim where I
need it. :-)

> +
> +	ret = of_property_read_string(dev->of_node, pname,
> +				(const char **) &led->label);
> +	if (ret < 0) {
> +		dev_err(dev, "Error reading %s Device Tree property (%d)\n",
> +			pname, ret);
> +		return ret;
> +	}
> +
> +	pname = "flash-timeout-microsec";
> +
> +	ret = of_property_read_u32(dev->of_node, pname, &led->max_flash_tm);
> +	if (ret) {
> +		dev_err(dev, "Error reading %s Device Tree property (%d)\n",
> +			pname, ret);
> +		return ret;
> +	}
> +
> +	return ret;

You always return ret whether here or above.

> +}
> +
> +static void aat1290_init_flash_settings(struct aat1290_led *led,
> +					 struct aat1290_led_settings *s)
> +{
> +	struct led_flash_setting *setting;
> +
> +	/* Init flash intensity setting */
> +	setting = &s->torch_brightness;
> +	/*
> +	 * Torch current is adjustable in logarithmic fashion and thus
> +	 * it is not possible to define fixed step in microamperes.
> +	 * Instead led brightness levels are used to make possible
> +	 * setting all the supported levels from V4L2 Flash sub-device.
> +	 */
> +	setting->min = 1;
> +	setting->max = AAT1290_MAX_MM_CURR_PERCENT_0 -
> +		       AAT1290_MAX_MM_CURR_PERCENT_100;
> +	setting->step = 1;
> +	setting->val = setting->max;
> +
> +	/* Init flash timeout setting */
> +	setting = &s->flash_timeout;
> +	setting->min = led->max_flash_tm / AAT1290_FLASH_TM_NUM_LEVELS;
> +	setting->max = setting->min * AAT1290_FLASH_TM_NUM_LEVELS;
> +	setting->step = setting->min;
> +	setting->val = setting->max;
> +}
> +
> +static const struct led_flash_ops flash_ops = {
> +	.strobe_set = aat1290_led_flash_strobe_set,
> +	.timeout_set = aat1290_led_flash_timeout_set,
> +};
> +
> +static int aat1290_led_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *dev_node = pdev->dev.of_node;
> +	struct aat1290_led *led;
> +	struct led_classdev *led_cdev;
> +	struct led_classdev_flash *flash;
> +	struct aat1290_led_settings settings;
> +	int flen_gpio, enset_gpio, ret;
> +
> +	led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
> +	if (!led)
> +		return -ENOMEM;
> +
> +	led->pdev = pdev;
> +	platform_set_drvdata(pdev, led);
> +
> +	if (!dev_node)
> +		return -ENXIO;
> +
> +	flen_gpio = of_get_gpio(dev_node, 0);
> +	if (gpio_is_valid(flen_gpio)) {
> +		ret = gpio_request_one(flen_gpio, GPIOF_DIR_OUT,
> +						"aat1290_flen");
> +		if (ret < 0) {
> +			dev_err(dev,
> +				"failed to request GPIO %d, error %d\n",
> +							flen_gpio, ret);
> +			goto error_gpio_flen;
> +		}
> +	}
> +	led->flen_gpio = flen_gpio;
> +
> +	enset_gpio = of_get_gpio(dev_node, 1);
> +	if (gpio_is_valid(enset_gpio)) {
> +		ret = gpio_request_one(enset_gpio, GPIOF_DIR_OUT,

Could you use devm_gpio_request_one()?

> +						"aat1290_en_set");
> +		if (ret < 0) {
> +			dev_err(dev,
> +				"failed to request GPIO %d, error %d\n",
> +							enset_gpio, ret);
> +			goto error_gpio_en_set;
> +		}
> +	}
> +	led->en_set_gpio = enset_gpio;
> +
> +	ret = aat1290_led_parse_dt(led, &pdev->dev);
> +	if (ret < 0)
> +		goto error_gpio_en_set;
> +
> +	mutex_init(&led->lock);

By moving mutex_init() up, you can avoid calling mutex_destroy() on an
uninitialised mutex in error paths.

> +
> +	flash = &led->ldev;
> +
> +	/* Init flash settings */
> +	aat1290_init_flash_settings(led, &settings);
> +
> +	flash->timeout = settings.flash_timeout;
> +
> +	/* Init led class */
> +	led_cdev = &flash->led_cdev;
> +	led_cdev->name = led->label;
> +	led_cdev->brightness_set = aat1290_led_brightness_set;
> +	led_cdev->brightness_set_sync = aat1290_led_brightness_set_sync;
> +	led_cdev->max_brightness = settings.torch_brightness.max;
> +	led_cdev->flags |= LED_DEV_CAP_FLASH;
> +
> +	INIT_WORK(&led->work_brightness_set, aat1290_brightness_set_work);
> +
> +	flash->ops = &flash_ops;
> +
> +	/* Register in the LED subsystem. */
> +	ret = led_classdev_flash_register(&pdev->dev, flash);
> +	if (ret < 0)
> +		goto error_gpio_en_set;
> +
> +	return 0;
> +
> +error_gpio_en_set:
> +	if (gpio_is_valid(enset_gpio))
> +		gpio_free(enset_gpio);
> +error_gpio_flen:
> +	if (gpio_is_valid(flen_gpio))
> +		gpio_free(flen_gpio);
> +	mutex_destroy(&led->lock);
> +
> +	return ret;
> +}
> +
> +static int aat1290_led_remove(struct platform_device *pdev)
> +{
> +	struct aat1290_led *led = platform_get_drvdata(pdev);
> +
> +	led_classdev_flash_unregister(&led->ldev);
> +	cancel_work_sync(&led->work_brightness_set);
> +
> +	if (gpio_is_valid(led->en_set_gpio))
> +		gpio_free(led->en_set_gpio);
> +	if (gpio_is_valid(led->flen_gpio))
> +		gpio_free(led->flen_gpio);
> +
> +	mutex_destroy(&led->lock);
> +
> +	return 0;
> +}
> +
> +static struct of_device_id aat1290_led_dt_match[] = {
> +	{.compatible = "skyworks,aat1290"},
> +	{},
> +};
> +
> +static struct platform_driver aat1290_led_driver = {
> +	.probe		= aat1290_led_probe,
> +	.remove		= aat1290_led_remove,
> +	.driver		= {
> +		.name	= "aat1290-led",
> +		.owner	= THIS_MODULE,
> +		.of_match_table = aat1290_led_dt_match,
> +	},
> +};
> +
> +module_platform_driver(aat1290_led_driver);
> +
> +MODULE_AUTHOR("Jacek Anaszewski <j.anaszewski@...sung.com>");
> +MODULE_DESCRIPTION("Skyworks Current Regulator for Flash LEDs");
> +MODULE_LICENSE("GPL");

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@....fi	XMPP: sailus@...iisi.org.uk
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