Message-id: <5489B995.7080209@samsung.com>
Date:	Thu, 11 Dec 2014 16:34:45 +0100
From:	Jacek Anaszewski <j.anaszewski@...sung.com>
To:	Sakari Ailus <sakari.ailus@....fi>
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 Sakari,

Thanks for the review.

On 12/11/2014 03:16 PM, Sakari Ailus wrote:
> 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.

Oops, I missed that.

>> +
>> +#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.

OK.

>> +#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?

OK.

>> +
>> +	/* 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?

This is minimal required time, so usleep_range could be used here,
which would however make the delay of setting the torch brightness
even more unstable.

>> +
>> +	/* 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?

It is used by led-triggers. They are still available as the torch
functionality is handled by the LED class.

>> +}
>> +
>> +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. :-)

I will also write them in verbatim, as I am doing it in the max77693-led
driver. Here I got influenced by some code few months ago probably :)

>> +
>> +	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.

Indeed, only the last occurrence should be left.

>> +}
>> +
>> +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()?

OK.

>> +						"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.

Right.

>> +
>> +	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");
>


-- 
Best Regards,
Jacek Anaszewski
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