leds: 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>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>
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(<3593_led_driver);
+}
+
+static void __exit lt3593_led_exit(void)
+{
+ platform_driver_unregister(<3593_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");