backlight: add driver for Bachmann's ot200

Add backlight driver for Bachmann's ot200 visualisation device.  The
driver uses MFGPT 7 of CS5535 silicon to regulate the backlight.

[akpm@linux-foundation.org: remove redundant test of `brightness']
Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Andres Salomon <dilinger@queued.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 183 insertions, 1 deletions

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 49e7d83f869f..248d6c0858dd 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -341,6 +341,13 @@ config BACKLIGHT_LP855X
           This supports TI LP8550, LP8551, LP8552, LP8553 and LP8556
           backlight driver.
 
+config BACKLIGHT_OT200
+        tristate "Backlight driver for ot200 visualisation device"
+        depends on BACKLIGHT_CLASS_DEVICE && CS5535_MFGPT
+        help
+          To compile this driver as a module, choose M here: the module will be
+          called ot200_bl.
+
 endif # BACKLIGHT_CLASS_DEVICE
 
 endif # BACKLIGHT_LCD_SUPPORT
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 0ee06e0832bd..c71dd793363d 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -39,4 +39,4 @@ obj-$(CONFIG_BACKLIGHT_ADP8870)	+= adp8870_bl.o
 obj-$(CONFIG_BACKLIGHT_88PM860X) += 88pm860x_bl.o
 obj-$(CONFIG_BACKLIGHT_PCF50633)        += pcf50633-backlight.o
 obj-$(CONFIG_BACKLIGHT_AAT2870) += aat2870_bl.o
-
+obj-$(CONFIG_BACKLIGHT_OT200) += ot200_bl.o
diff --git a/drivers/video/backlight/ot200_bl.c b/drivers/video/backlight/ot200_bl.c
new file mode 100644
index 000000000000..f519d55a294c
--- /dev/null
+++ b/drivers/video/backlight/ot200_bl.c
@@ -0,0 +1,175 @@
+/*
+ * Copyright (C) 2012 Bachmann electronic GmbH
+ *      Christian Gmeiner <christian.gmeiner@gmail.com>
+ *
+ * Backlight driver for ot200 visualisation device from
+ * Bachmann electronic GmbH.
+ *
+ * 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/module.h>
+#include <linux/fb.h>
+#include <linux/backlight.h>
+#include <linux/gpio.h>
+#include <linux/cs5535.h>
+
+static struct cs5535_mfgpt_timer *pwm_timer;
+
+/* this array defines the mapping of brightness in % to pwm frequency */
+static const u8 dim_table[101] = {0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2,
+                                  2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4,
+                                  4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 9,
+                                  10, 10, 11, 11, 12, 12, 13, 14, 15, 15, 16,
+                                  17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28,
+                                  30, 31, 33, 35, 37, 39, 41, 43, 45, 47, 50,
+                                  53, 55, 58, 61, 65, 68, 72, 75, 79, 84, 88,
+                                  93, 97, 103, 108, 114, 120, 126, 133, 140,
+                                  147, 155, 163};
+
+struct ot200_backlight_data {
+        int current_brightness;
+};
+
+#define GPIO_DIMM       27
+#define SCALE           1
+#define CMP1MODE        0x2     /* compare on GE; output high on compare
+                                 * greater than or equal */
+#define PWM_SETUP       (SCALE | CMP1MODE << 6 | MFGPT_SETUP_CNTEN)
+#define MAX_COMP2       163
+
+static int ot200_backlight_update_status(struct backlight_device *bl)
+{
+        struct ot200_backlight_data *data = bl_get_data(bl);
+        int brightness = bl->props.brightness;
+
+        if (bl->props.state & BL_CORE_FBBLANK)
+                brightness = 0;
+
+        /* enable or disable PWM timer */
+        if (brightness == 0)
+                cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, 0);
+        else if (data->current_brightness == 0) {
+                cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
+                cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP,
+                        MFGPT_SETUP_CNTEN);
+        }
+
+        /* apply new brightness value */
+        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
+                MAX_COMP2 - dim_table[brightness]);
+        data->current_brightness = brightness;
+
+        return 0;
+}
+
+static int ot200_backlight_get_brightness(struct backlight_device *bl)
+{
+        struct ot200_backlight_data *data = bl_get_data(bl);
+        return data->current_brightness;
+}
+
+static const struct backlight_ops ot200_backlight_ops = {
+        .update_status  = ot200_backlight_update_status,
+        .get_brightness = ot200_backlight_get_brightness,
+};
+
+static int ot200_backlight_probe(struct platform_device *pdev)
+{
+        struct backlight_device *bl;
+        struct ot200_backlight_data *data;
+        struct backlight_properties props;
+        int retval = 0;
+
+        /* request gpio */
+        if (gpio_request(GPIO_DIMM, "ot200 backlight dimmer") < 0) {
+                dev_err(&pdev->dev, "failed to request GPIO %d\n", GPIO_DIMM);
+                return -ENODEV;
+        }
+
+        /* request timer */
+        pwm_timer = cs5535_mfgpt_alloc_timer(7, MFGPT_DOMAIN_ANY);
+        if (!pwm_timer) {
+                dev_err(&pdev->dev, "MFGPT 7 not available\n");
+                retval = -ENODEV;
+                goto error_mfgpt_alloc;
+        }
+
+        data = kzalloc(sizeof(*data), GFP_KERNEL);
+        if (!data) {
+                retval = -ENOMEM;
+                goto error_kzalloc;
+        }
+
+        /* setup gpio */
+        cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_ENABLE);
+        cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_AUX1);
+
+        /* setup timer */
+        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1, 0);
+        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP2, MAX_COMP2);
+        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, PWM_SETUP);
+
+        data->current_brightness = 100;
+        props.max_brightness = 100;
+        props.brightness = 100;
+        props.type = BACKLIGHT_RAW;
+
+        bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, data,
+                                        &ot200_backlight_ops, &props);
+        if (IS_ERR(bl)) {
+                dev_err(&pdev->dev, "failed to register backlight\n");
+                retval = PTR_ERR(bl);
+                goto error_backlight_device_register;
+        }
+
+        platform_set_drvdata(pdev, bl);
+
+        return 0;
+
+error_backlight_device_register:
+        kfree(data);
+error_kzalloc:
+        cs5535_mfgpt_free_timer(pwm_timer);
+error_mfgpt_alloc:
+        gpio_free(GPIO_DIMM);
+        return retval;
+}
+
+static int ot200_backlight_remove(struct platform_device *pdev)
+{
+        struct backlight_device *bl = platform_get_drvdata(pdev);
+        struct ot200_backlight_data *data = bl_get_data(bl);
+
+        backlight_device_unregister(bl);
+
+        /* on module unload set brightness to 100% */
+        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
+        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);
+        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
+                MAX_COMP2 - dim_table[100]);
+
+        cs5535_mfgpt_free_timer(pwm_timer);
+        gpio_free(GPIO_DIMM);
+
+        kfree(data);
+        return 0;
+}
+
+static struct platform_driver ot200_backlight_driver = {
+        .driver         = {
+                .name   = "ot200-backlight",
+                .owner  = THIS_MODULE,
+        },
+        .probe          = ot200_backlight_probe,
+        .remove         = ot200_backlight_remove,
+};
+
+module_platform_driver(ot200_backlight_driver);
+
+MODULE_DESCRIPTION("backlight driver for ot200 visualisation device");
+MODULE_AUTHOR("Christian Gmeiner <christian.gmeiner@gmail.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ot200-backlight");