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>

3 files changed, 226 insertions, 0 deletions

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index e481d3c52a54..e2b7a5382ae6 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -245,6 +245,14 @@ config LEDS_INTEL_SS4200
           drive or power LEDs on the front panel.  Using this driver
           can stop the front LED from blinking after startup.
 
+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 12b7a20fcfe0..eb5a141d825c 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -30,6 +30,7 @@ obj-$(CONFIG_LEDS_WM831X_STATUS)	+= leds-wm831x-status.o
 obj-$(CONFIG_LEDS_WM8350)               += leds-wm8350.o
 obj-$(CONFIG_LEDS_PWM)                  += leds-pwm.o
 obj-$(CONFIG_LEDS_INTEL_SS4200)         += leds-ss4200.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 000000000000..fee40a841959
--- /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");