Re: [PATCH] LED: add driver for LT3593 controlled LEDs

[Daniel Mack <daniel@caiaq.de>]

Hi Richard,

Excuse the annoyance - I just want to make sure this is not getting
lost ...

Thanks,
Daniel


On Thu, Oct 15, 2009 at 02:59:35AM +0200, Daniel Mack wrote:
> Date: Thu, 15 Oct 2009 02:59:35 +0200
> From: Daniel Mack <daniel@caiaq.de>
> To: Richard Purdie <rpurdie@rpsys.net>
> Cc: linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] LED: add driver for LT3593 controlled LEDs
> 
> Hi,
> 
> thanks for the careful review!
> 
> On Wed, Oct 14, 2009 at 07:13:21PM +0100, Richard Purdie wrote:
> > On Wed, 2009-10-07 at 05:41 +0800, Daniel Mack wrote:
> > > The LT3593 is a step-up DC/DC converter designed to drive up to ten
> > > white LEDs in series. The current flow can be set with a control pin.
> > > 
> > > This driver controls any number of such devices connected on generic
> > > GPIOs and exports the function as as platform_driver.
> > > 
> > > The gpio_led platform data struct definition is reused for this purpose.
> > > 
> > > Successfully tested on a PXA embedded board.
> > 
> > Looks good to me, just some minor comments:
> > 
> > > +
> > > +#include <linux/kernel.h>
> > > +#include <linux/init.h>
> > > +#include <linux/platform_device.h>
> > > +#include <linux/leds.h>
> > > +#include <linux/workqueue.h>
> > > +#include <linux/delay.h>
> > > +
> > > +#include <asm/gpio.h>
> > 
> > Should this be <linux/gpio.h> ?
> 
> Yep, correct. As this is taken from leds-gpio, the original version
> should need an update, too.
> 
> > > +static void lt3593_led_work(struct work_struct *work)
> > > +{
> > > +	int pulses;
> > > +	struct lt3593_led_data	*led_dat =
> > > +		container_of(work, struct lt3593_led_data, work);
> > 
> > There's a tab above which caught my eye. I'd have ignored it if I wasn't
> > mentioning the above...
> 
> Fixed.
> 
> > > +	pulses = 32 - (led_dat->new_level * 32) / 255;
> > > +
> > > +	if (pulses == 0) {
> > > +		gpio_set_value_cansleep(led_dat->gpio, 0);
> > > +		mdelay(1);
> > > +		gpio_set_value_cansleep(led_dat->gpio, 1);
> > > +		return;
> > > +	}
> > 
> > mdelay is frowned upon
> > 
> > > +	gpio_set_value_cansleep(led_dat->gpio, 1);
> > > +
> > > +	while (pulses--) {
> > > +		gpio_set_value_cansleep(led_dat->gpio, 0);
> > > +		udelay(1);
> > > +		gpio_set_value_cansleep(led_dat->gpio, 1);
> > > +		udelay(1);
> > > +	}
> > 
> > and likewise udelay but I guess we can't do much else with this
> > hardware...
> > 
> > Otherwise it looks good, just check the include please and then I'll
> > apply it.
> 
> Thanks! New patch below.
> 
> Daniel
> 
> From c1024d34445d19abe53d80756b2439521ad03579 Mon Sep 17 00:00:00 2001
> From: Daniel Mack <daniel@caiaq.de>
> Date: Wed, 7 Oct 2009 04:11:40 +0800
> Subject: [PATCH] LED: add driver for LT3593 controlled LEDs
> 
> The LT3593 is a step-up DC/DC converter designed to drive up to ten
> white LEDs in series. The current flow can be set with a control pin.
> 
> This driver controls any number of such devices connected on generic
> GPIOs and exports the function as as platform_driver.
> 
> The gpio_led platform data struct definition is reused for this purpose.
> 
> Successfully tested on a PXA embedded board.
> 
> Signed-off-by: Daniel Mack <daniel@caiaq.de>
> Cc: Richard Purdie <rpurdie@rpsys.net>
> ---
>  drivers/leds/Kconfig       |    8 ++
>  drivers/leds/Makefile      |    1 +
>  drivers/leds/leds-lt3593.c |  217 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 226 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/leds/leds-lt3593.c
> 
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 7c8e712..80a183f 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -229,6 +229,14 @@ config LEDS_BD2802
>  	  This option enables support for BD2802GU RGB LED driver chips
>  	  accessed via the I2C bus.
>  
> +config LEDS_LT3593
> +	tristate "LED driver for LT3593 controllers"
> +	depends on LEDS_CLASS && GENERIC_GPIO
> +	help
> +	  This option enables support for LEDs driven by a Linear Technology
> +	  LT3593 controller. This controller uses a special one-wire pulse
> +	  coding protocol to set the brightness.
> +
>  comment "LED Triggers"
>  
>  config LEDS_TRIGGERS
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index e8cdcf7..3d79287 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_LEDS_PCA955X)		+= leds-pca955x.o
>  obj-$(CONFIG_LEDS_DA903X)		+= leds-da903x.o
>  obj-$(CONFIG_LEDS_WM8350)		+= leds-wm8350.o
>  obj-$(CONFIG_LEDS_PWM)			+= leds-pwm.o
> +obj-$(CONFIG_LEDS_LT3593)		+= leds-lt3593.o
>  
>  # LED SPI Drivers
>  obj-$(CONFIG_LEDS_DAC124S085)		+= leds-dac124s085.o
> diff --git a/drivers/leds/leds-lt3593.c b/drivers/leds/leds-lt3593.c
> new file mode 100644
> index 0000000..fee40a8
> --- /dev/null
> +++ b/drivers/leds/leds-lt3593.c
> @@ -0,0 +1,217 @@
> +/*
> + * LEDs driver for LT3593 controllers
> + *
> + * See the datasheet at http://cds.linear.com/docs/Datasheet/3593f.pdf
> + *
> + * Copyright (c) 2009 Daniel Mack <daniel@caiaq.de>
> + *
> + * Based on leds-gpio.c,
> + *
> + *   Copyright (C) 2007 8D Technologies inc.
> + *   Raphael Assenat <raph@8d.com>
> + *   Copyright (C) 2008 Freescale Semiconductor, Inc.
> + *
> + * 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/kernel.h>
> +#include <linux/init.h>
> +#include <linux/platform_device.h>
> +#include <linux/leds.h>
> +#include <linux/workqueue.h>
> +#include <linux/delay.h>
> +#include <linux/gpio.h>
> +
> +struct lt3593_led_data {
> +	struct led_classdev cdev;
> +	unsigned gpio;
> +	struct work_struct work;
> +	u8 new_level;
> +};
> +
> +static void lt3593_led_work(struct work_struct *work)
> +{
> +	int pulses;
> +	struct lt3593_led_data *led_dat =
> +		container_of(work, struct lt3593_led_data, work);
> +
> +	/*
> +	 * The LT3593 resets its internal current level register to the maximum
> +	 * level on the first falling edge on the control pin. Each following
> +	 * falling edge decreases the current level by 625uA. Up to 32 pulses
> +	 * can be sent, so the maximum power reduction is 20mA.
> +	 * After a timeout of 128us, the value is taken from the register and
> +	 * applied is to the output driver.
> +	 */
> +
> +	if (led_dat->new_level == 0) {
> +		gpio_set_value_cansleep(led_dat->gpio, 0);
> +		return;
> +	}
> +
> +	pulses = 32 - (led_dat->new_level * 32) / 255;
> +
> +	if (pulses == 0) {
> +		gpio_set_value_cansleep(led_dat->gpio, 0);
> +		mdelay(1);
> +		gpio_set_value_cansleep(led_dat->gpio, 1);
> +		return;
> +	}
> +
> +	gpio_set_value_cansleep(led_dat->gpio, 1);
> +
> +	while (pulses--) {
> +		gpio_set_value_cansleep(led_dat->gpio, 0);
> +		udelay(1);
> +		gpio_set_value_cansleep(led_dat->gpio, 1);
> +		udelay(1);
> +	}
> +}
> +
> +static void lt3593_led_set(struct led_classdev *led_cdev,
> +	enum led_brightness value)
> +{
> +	struct lt3593_led_data *led_dat =
> +		container_of(led_cdev, struct lt3593_led_data, cdev);
> +
> +	led_dat->new_level = value;
> +	schedule_work(&led_dat->work);
> +}
> +
> +static int __devinit create_lt3593_led(const struct gpio_led *template,
> +	struct lt3593_led_data *led_dat, struct device *parent)
> +{
> +	int ret, state;
> +
> +	/* skip leds on GPIOs that aren't available */
> +	if (!gpio_is_valid(template->gpio)) {
> +		printk(KERN_INFO "%s: skipping unavailable LT3593 LED at gpio %d (%s)\n",
> +				KBUILD_MODNAME, template->gpio, template->name);
> +		return 0;
> +	}
> +
> +	ret = gpio_request(template->gpio, template->name);
> +	if (ret < 0)
> +		return ret;
> +
> +	led_dat->cdev.name = template->name;
> +	led_dat->cdev.default_trigger = template->default_trigger;
> +	led_dat->gpio = template->gpio;
> +
> +	led_dat->cdev.brightness_set = lt3593_led_set;
> +
> +	state = (template->default_state == LEDS_GPIO_DEFSTATE_ON);
> +	led_dat->cdev.brightness = state ? LED_FULL : LED_OFF;
> +
> +	if (!template->retain_state_suspended)
> +		led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
> +
> +	ret = gpio_direction_output(led_dat->gpio, state);
> +	if (ret < 0)
> +		goto err;
> +
> +	INIT_WORK(&led_dat->work, lt3593_led_work);
> +
> +	ret = led_classdev_register(parent, &led_dat->cdev);
> +	if (ret < 0)
> +		goto err;
> +
> +	printk(KERN_INFO "%s: registered LT3593 LED '%s' at GPIO %d\n",
> +		KBUILD_MODNAME, template->name, template->gpio);
> +
> +	return 0;
> +
> +err:
> +	gpio_free(led_dat->gpio);
> +	return ret;
> +}
> +
> +static void delete_lt3593_led(struct lt3593_led_data *led)
> +{
> +	if (!gpio_is_valid(led->gpio))
> +		return;
> +
> +	led_classdev_unregister(&led->cdev);
> +	cancel_work_sync(&led->work);
> +	gpio_free(led->gpio);
> +}
> +
> +static int __devinit lt3593_led_probe(struct platform_device *pdev)
> +{
> +	struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
> +	struct lt3593_led_data *leds_data;
> +	int i, ret = 0;
> +
> +	if (!pdata)
> +		return -EBUSY;
> +
> +	leds_data = kzalloc(sizeof(struct lt3593_led_data) * pdata->num_leds,
> +				GFP_KERNEL);
> +	if (!leds_data)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < pdata->num_leds; i++) {
> +		ret = create_lt3593_led(&pdata->leds[i], &leds_data[i],
> +				      &pdev->dev);
> +		if (ret < 0)
> +			goto err;
> +	}
> +
> +	platform_set_drvdata(pdev, leds_data);
> +
> +	return 0;
> +
> +err:
> +	for (i = i - 1; i >= 0; i--)
> +		delete_lt3593_led(&leds_data[i]);
> +
> +	kfree(leds_data);
> +
> +	return ret;
> +}
> +
> +static int __devexit lt3593_led_remove(struct platform_device *pdev)
> +{
> +	int i;
> +	struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
> +	struct lt3593_led_data *leds_data;
> +
> +	leds_data = platform_get_drvdata(pdev);
> +
> +	for (i = 0; i < pdata->num_leds; i++)
> +		delete_lt3593_led(&leds_data[i]);
> +
> +	kfree(leds_data);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver lt3593_led_driver = {
> +	.probe		= lt3593_led_probe,
> +	.remove		= __devexit_p(lt3593_led_remove),
> +	.driver		= {
> +		.name	= "leds-lt3593",
> +		.owner	= THIS_MODULE,
> +	},
> +};
> +
> +MODULE_ALIAS("platform:leds-lt3593");
> +
> +static int __init lt3593_led_init(void)
> +{
> +	return platform_driver_register(&lt3593_led_driver);
> +}
> +
> +static void __exit lt3593_led_exit(void)
> +{
> +	platform_driver_unregister(&lt3593_led_driver);
> +}
> +
> +module_init(lt3593_led_init);
> +module_exit(lt3593_led_exit);
> +
> +MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>");
> +MODULE_DESCRIPTION("LED driver for LT3593 controllers");
> +MODULE_LICENSE("GPL");
> -- 
> 1.6.0.4
>